When calling hugetlb_resv_map_add(), we've guaranteed that the parameter
'to' is always larger than 'from', so it never returns a negative value
from hugetlb_resv_map_add(). Thus remove the redundant VM_BUG_ON().
Link: https://lkml.kernel.org/r/2b565552f3d06753da1e8dda439c0d96d6d9a5a3.1634797639.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The callers of has_same_uncharge_info() has accessed the original
file_region and new file_region, and they are impossible to be NULL now.
So we can remove the file_region validation in has_same_uncharge_info()
to simplify the code.
Link: https://lkml.kernel.org/r/97fc68d3f8d34f63c204645e10d7a718997e50b7.1634797639.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After commit 8382d914eb ("mm, hugetlb: improve page-fault
scalability"), the hugetlb_instantiation_mutex lock had been replaced by
hugetlb_fault_mutex_table to serializes faults on the same logical page.
Thus update the obsolete hugetlb_instantiation_mutex related comments.
Link: https://lkml.kernel.org/r/4b3febeae37455ff7b74aa0aad16cc6909cf0926.1634797639.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now the size of CMA area for gigantic hugepages runtime allocation is
balanced for all online nodes, but we also want to specify the size of
CMA per-node, or only one node in some cases, which are similar with
patch [1].
For example, on some multi-nodes systems, each node's memory can be
different, allocating the same size of CMA for each node is not suitable
for the low-memory nodes. Meanwhile some workloads like DPDK mentioned
by Zhenguo in patch [1] only need hugepages in one node.
On the other hand, we have some machines with multiple types of memory,
like DRAM and PMEM (persistent memory). On this system, we may want to
specify all the hugepages only on DRAM node, or specify the proportion
of DRAM node and PMEM node, to tuning the performance of the workloads.
Thus this patch adds node format for 'hugetlb_cma' parameter to support
specifying the size of CMA per-node. An example is as follows:
hugetlb_cma=0:5G,2:5G
which means allocating 5G size of CMA area on node 0 and node 2
respectively. And the users should use the node specific sysfs file to
allocate the gigantic hugepages if specified the CMA size on that node.
Link: https://lkml.kernel.org/r/20211005054729.86457-1-yaozhenguo1@gmail.com [1]
Link: https://lkml.kernel.org/r/bb790775ca60bb8f4b26956bb3f6988f74e075c7.1634261144.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Support mremap() for hugepage backed vma segment by simply repositioning
page table entries. The page table entries are repositioned to the new
virtual address on mremap().
Hugetlb mremap() support is of course generic; my motivating use case is
a library (hugepage_text), which reloads the ELF text of executables in
hugepages. This significantly increases the execution performance of
said executables.
Restrict the mremap operation on hugepages to up to the size of the
original mapping as the underlying hugetlb reservation is not yet
capable of handling remapping to a larger size.
During the mremap() operation we detect pmd_share'd mappings and we
unshare those during the mremap(). On access and fault the sharing is
established again.
Link: https://lkml.kernel.org/r/20211013195825.3058275-1-almasrymina@google.com
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Ken Chen <kenchen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Kirill Shutemov <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Demote page functionality will split a huge page into a number of huge
pages of a smaller size. For example, on x86 a 1GB huge page can be
demoted into 512 2M huge pages. Demotion is done 'in place' by simply
splitting the huge page.
Added '*_for_demote' wrappers for remove_hugetlb_page,
destroy_compound_hugetlb_page and prep_compound_gigantic_page for use by
demote code.
[mike.kravetz@oracle.com: v4]
Link: https://lkml.kernel.org/r/6ca29b8e-527c-d6ec-900e-e6a43e4f8b73@oracle.com
Link: https://lkml.kernel.org/r/20211007181918.136982-6-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Nghia Le <nghialm78@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The routines remove_hugetlb_page and destroy_compound_gigantic_page will
remove a gigantic page and make the set of base pages ready to be
returned to a lower level allocator. In the process of doing this, they
make all base pages reference counted.
The routine prep_compound_gigantic_page creates a gigantic page from a
set of base pages. It assumes that all these base pages are reference
counted.
During demotion, a gigantic page will be split into huge pages of a
smaller size. This logically involves use of the routines,
remove_hugetlb_page, and destroy_compound_gigantic_page followed by
prep_compound*_page for each smaller huge page.
When pages are reference counted (ref count >= 0), additional
speculative ref counts could be taken as described in previous commits
[1] and [2]. This could result in errors while demoting a huge page.
Quite a bit of code would need to be created to handle all possible
issues.
Instead of dealing with the possibility of speculative ref counts, avoid
the possibility by keeping ref counts at zero during the demote process.
Add a boolean 'demote' to the routines remove_hugetlb_page,
destroy_compound_gigantic_page and prep_compound_gigantic_page. If the
boolean is set, the remove and destroy routines will not reference count
pages and the prep routine will not expect reference counted pages.
'*_for_demote' wrappers of the routines will be added in a subsequent
patch where this functionality is used.
[1] https://lore.kernel.org/linux-mm/20210622021423.154662-3-mike.kravetz@oracle.com/
[2] https://lore.kernel.org/linux-mm/20210809184832.18342-3-mike.kravetz@oracle.com/
Link: https://lkml.kernel.org/r/20211007181918.136982-5-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Nghia Le <nghialm78@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When huge page demotion is fully implemented, gigantic pages can be
demoted to a smaller huge page size. For example, on x86 a 1G page can
be demoted to 512 2M pages. However, gigantic pages can potentially be
allocated from CMA. If a gigantic page which was allocated from CMA is
demoted, the corresponding demoted pages needs to be returned to CMA.
Use the new interface cma_pages_valid() to determine if a non-gigantic
hugetlb page should be freed to CMA. Also, clear mapping field of these
pages as expected by cma_release.
This also requires a change to CMA region creation for gigantic pages.
CMA uses a per-region bit map to track allocations. When setting up the
region, you specify how many pages each bit represents. Currently, only
gigantic pages are allocated/freed from CMA so the region is set up such
that one bit represents a gigantic page size allocation.
With demote, a gigantic page (allocation) could be split into smaller
size pages. And, these smaller size pages will be freed to CMA. So,
since the per-region bit map needs to be set up to represent the
smallest allocation/free size, it now needs to be set to the smallest
huge page size which can be freed to CMA.
Unfortunately, we set up the CMA region for huge pages before we set up
huge pages sizes (hstates). So, technically we do not know the smallest
huge page size as this can change via command line options and
architecture specific code. Therefore, at region setup time we use
HUGETLB_PAGE_ORDER as the smallest possible huge page size that can be
given back to CMA. It is possible that this value is sub-optimal for
some architectures/config options. If needed, this can be addressed in
follow on work.
Link: https://lkml.kernel.org/r/20211007181918.136982-4-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Nghia Le <nghialm78@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "hugetlb: add demote/split page functionality", v4.
The concurrent use of multiple hugetlb page sizes on a single system is
becoming more common. One of the reasons is better TLB support for
gigantic page sizes on x86 hardware. In addition, hugetlb pages are
being used to back VMs in hosting environments.
When using hugetlb pages to back VMs, it is often desirable to
preallocate hugetlb pools. This avoids the delay and uncertainty of
allocating hugetlb pages at VM startup. In addition, preallocating huge
pages minimizes the issue of memory fragmentation that increases the
longer the system is up and running.
In such environments, a combination of larger and smaller hugetlb pages
are preallocated in anticipation of backing VMs of various sizes. Over
time, the preallocated pool of smaller hugetlb pages may become depleted
while larger hugetlb pages still remain. In such situations, it is
desirable to convert larger hugetlb pages to smaller hugetlb pages.
Converting larger to smaller hugetlb pages can be accomplished today by
first freeing the larger page to the buddy allocator and then allocating
the smaller pages. For example, to convert 50 GB pages on x86:
gb_pages=`cat .../hugepages-1048576kB/nr_hugepages`
m2_pages=`cat .../hugepages-2048kB/nr_hugepages`
echo $(($gb_pages - 50)) > .../hugepages-1048576kB/nr_hugepages
echo $(($m2_pages + 25600)) > .../hugepages-2048kB/nr_hugepages
On an idle system this operation is fairly reliable and results are as
expected. The number of 2MB pages is increased as expected and the time
of the operation is a second or two.
However, when there is activity on the system the following issues
arise:
1) This process can take quite some time, especially if allocation of
the smaller pages is not immediate and requires migration/compaction.
2) There is no guarantee that the total size of smaller pages allocated
will match the size of the larger page which was freed. This is
because the area freed by the larger page could quickly be
fragmented.
In a test environment with a load that continually fills the page cache
with clean pages, results such as the following can be observed:
Unexpected number of 2MB pages allocated: Expected 25600, have 19944
real 0m42.092s
user 0m0.008s
sys 0m41.467s
To address these issues, introduce the concept of hugetlb page demotion.
Demotion provides a means of 'in place' splitting of a hugetlb page to
pages of a smaller size. This avoids freeing pages to buddy and then
trying to allocate from buddy.
Page demotion is controlled via sysfs files that reside in the per-hugetlb
page size and per node directories.
- demote_size
Target page size for demotion, a smaller huge page size. File
can be written to chose a smaller huge page size if multiple are
available.
- demote
Writable number of hugetlb pages to be demoted
To demote 50 GB huge pages, one would:
cat .../hugepages-1048576kB/free_hugepages /* optional, verify free pages */
cat .../hugepages-1048576kB/demote_size /* optional, verify target size */
echo 50 > .../hugepages-1048576kB/demote
Only hugetlb pages which are free at the time of the request can be
demoted. Demotion does not add to the complexity of surplus pages and
honors reserved huge pages. Therefore, when a value is written to the
sysfs demote file, that value is only the maximum number of pages which
will be demoted. It is possible fewer will actually be demoted. The
recently introduced per-hstate mutex is used to synchronize demote
operations with other operations that modify hugetlb pools.
Real world use cases
--------------------
The above scenario describes a real world use case where hugetlb pages
are used to back VMs on x86. Both issues of long allocation times and
not necessarily getting the expected number of smaller huge pages after
a free and allocate cycle have been experienced. The occurrence of
these issues is dependent on other activity within the host and can not
be predicted.
This patch (of 5):
Two new sysfs files are added to demote hugtlb pages. These files are
both per-hugetlb page size and per node. Files are:
demote_size - The size in Kb that pages are demoted to. (read-write)
demote - The number of huge pages to demote. (write-only)
By default, demote_size is the next smallest huge page size. Valid huge
page sizes less than huge page size may be written to this file. When
huge pages are demoted, they are demoted to this size.
Writing a value to demote will result in an attempt to demote that
number of hugetlb pages to an appropriate number of demote_size pages.
NOTE: Demote interfaces are only provided for huge page sizes if there
is a smaller target demote huge page size. For example, on x86 1GB huge
pages will have demote interfaces. 2MB huge pages will not have demote
interfaces.
This patch does not provide full demote functionality. It only provides
the sysfs interfaces.
It also provides documentation for the new interfaces.
[mike.kravetz@oracle.com: n_mask initialization does not need to be protected by the mutex]
Link: https://lkml.kernel.org/r/0530e4ef-2492-5186-f919-5db68edea654@oracle.com
Link: https://lkml.kernel.org/r/20211007181918.136982-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: David Rientjes <rientjes@google.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Nghia Le <nghialm78@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Remove __unmap_hugepage_range() from the header file, because it is only
used in hugetlb.c.
Link: https://lkml.kernel.org/r/20210917165108.9341-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the folio equivalent of migrate_page_copy(), which is retained
as a wrapper for filesystems which are not yet converted to folios.
Also convert copy_huge_page() to folio_copy().
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Guillaume Morin reported hitting the following WARNING followed by GPF or
NULL pointer deference either in cgroups_destroy or in the kill_css path.:
percpu ref (css_release) <= 0 (-1) after switching to atomic
WARNING: CPU: 23 PID: 130 at lib/percpu-refcount.c:196 percpu_ref_switch_to_atomic_rcu+0x127/0x130
CPU: 23 PID: 130 Comm: ksoftirqd/23 Kdump: loaded Tainted: G O 5.10.60 #1
RIP: 0010:percpu_ref_switch_to_atomic_rcu+0x127/0x130
Call Trace:
rcu_core+0x30f/0x530
rcu_core_si+0xe/0x10
__do_softirq+0x103/0x2a2
run_ksoftirqd+0x2b/0x40
smpboot_thread_fn+0x11a/0x170
kthread+0x10a/0x140
ret_from_fork+0x22/0x30
Upon further examination, it was discovered that the css structure was
associated with hugetlb reservations.
For private hugetlb mappings the vma points to a reserve map that
contains a pointer to the css. At mmap time, reservations are set up
and a reference to the css is taken. This reference is dropped in the
vma close operation; hugetlb_vm_op_close. However, if a vma is split no
additional reference to the css is taken yet hugetlb_vm_op_close will be
called twice for the split vma resulting in an underflow.
Fix by taking another reference in hugetlb_vm_op_open. Note that the
reference is only taken for the owner of the reserve map. In the more
common fork case, the pointer to the reserve map is cleared for
non-owning vmas.
Link: https://lkml.kernel.org/r/20210830215015.155224-1-mike.kravetz@oracle.com
Fixes: e9fe92ae0c ("hugetlb_cgroup: add reservation accounting for private mappings")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Guillaume Morin <guillaume@morinfr.org>
Suggested-by: Guillaume Morin <guillaume@morinfr.org>
Tested-by: Guillaume Morin <guillaume@morinfr.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When removing a hugetlb page from the pool the ref count is set to one (as
the free page has no ref count) and compound page destructor is set to
NULL_COMPOUND_DTOR. Since a subsequent call to free the hugetlb page will
call __free_pages for non-gigantic pages and free_gigantic_page for
gigantic pages the destructor is not used.
However, consider the following race with code taking a speculative
reference on the page:
Thread 0 Thread 1
-------- --------
remove_hugetlb_page
set_page_refcounted(page);
set_compound_page_dtor(page,
NULL_COMPOUND_DTOR);
get_page_unless_zero(page)
__update_and_free_page
__free_pages(page,
huge_page_order(h));
/* Note that __free_pages() will simply drop
the reference to the page. */
put_page(page)
__put_compound_page()
destroy_compound_page
NULL_COMPOUND_DTOR
BUG: kernel NULL pointer
dereference, address:
0000000000000000
To address this race, set the dtor to the normal compound page dtor for
non-gigantic pages. The dtor for gigantic pages does not matter as
gigantic pages are changed from a compound page to 'just a group of pages'
before freeing. Hence, the destructor is not used.
Link: https://lkml.kernel.org/r/20210809184832.18342-4-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Mina Almasry <almasrymina@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When discussing the possibility of inflated page ref counts, Muuchun Song
pointed out this potential issue [1]. It is true that any code could
potentially take a reference on a compound page after allocation and
before it is converted to and put into use as a hugetlb page.
Specifically, this could be done by any users of get_page_unless_zero.
There are three areas of concern within hugetlb code.
1) When adding pages to the pool. In this case, new pages are
allocated added to the pool by calling put_page to invoke the hugetlb
destructor (free_huge_page). If there is an inflated ref count on the
page, it will not be immediately added to the free list. It will only
be added to the free list when the temporary ref count is dropped.
This is deemed acceptable and will not be addressed.
2) A page is allocated for immediate use normally as a surplus page or
migration target. In this case, the user of the page will also hold a
reference. There is no issue as this is just like normal page ref
counting.
3) A page is allocated and MUST be added to the free list to satisfy a
reservation. One such example is gather_surplus_pages as pointed out
by Muchun in [1]. More specifically, this case covers callers of
enqueue_huge_page where the page reference count must be zero. This
patch covers this third case.
Three routines call enqueue_huge_page when the page reference count could
potentially be inflated. They are: gather_surplus_pages,
alloc_and_dissolve_huge_page and add_hugetlb_page.
add_hugetlb_page is called on error paths when a huge page can not be
freed due to the inability to allocate vmemmap pages. In this case, the
temporairly inflated ref count is not an issue. When the ref is dropped
the appropriate action will be taken. Instead of VM_BUG_ON if the ref
count does not drop to zero, simply return.
In gather_surplus_pages and alloc_and_dissolve_huge_page the caller
expects a page (or pages) to be put on the free lists. In this case we
must ensure there are no temporary ref counts. We do this by calling
put_page_testzero() earlier and not using pages without a zero ref count.
The temporary page flag (HPageTemporary) is used in such cases so that as
soon as the inflated ref count is dropped the page will be freed.
[1] https://lore.kernel.org/linux-mm/CAMZfGtVMn3daKrJwZMaVOGOaJU+B4dS--x_oPmGQMD=c=QNGEg@mail.gmail.com/
Link: https://lkml.kernel.org/r/20210809184832.18342-3-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Code in prep_compound_gigantic_page waits for a rcu grace period if it
notices a temporarily inflated ref count on a tail page. This was due to
the identified potential race with speculative page cache references which
could only last for a rcu grace period. This is overly complicated as
this situation is VERY unlikely to ever happen. Instead, just quickly
return an error.
Also, only print a warning in prep_compound_gigantic_page instead of
multiple callers.
Link: https://lkml.kernel.org/r/20210809184832.18342-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
syzbot hit kernel BUG at fs/hugetlbfs/inode.c:532 as described in [1].
This BUG triggers if the HPageRestoreReserve flag is set on a page in
the page cache. It should never be set, as the routine
huge_add_to_page_cache explicitly clears the flag after adding a page to
the cache.
The only code other than huge page allocation which sets the flag is
restore_reserve_on_error. It will potentially set the flag in rare out
of memory conditions. syzbot was injecting errors to cause memory
allocation errors which exercised this specific path.
The code in restore_reserve_on_error is doing the right thing. However,
there are instances where pages in the page cache were being passed to
restore_reserve_on_error. This is incorrect, as once a page goes into
the cache reservation information will not be modified for the page
until it is removed from the cache. Error paths do not remove pages
from the cache, so even in the case of error, the page will remain in
the cache and no reservation adjustment is needed.
Modify routines that potentially call restore_reserve_on_error with a
page cache page to no longer do so.
Note on fixes tag: Prior to commit 846be08578 ("mm/hugetlb: expand
restore_reserve_on_error functionality") the routine would not process
page cache pages because the HPageRestoreReserve flag is not set on such
pages. Therefore, this issue could not be trigggered. The code added
by commit 846be08578 ("mm/hugetlb: expand restore_reserve_on_error
functionality") is needed and correct. It exposed incorrect calls to
restore_reserve_on_error which is the root cause addressed by this
commit.
[1] https://lore.kernel.org/linux-mm/00000000000050776d05c9b7c7f0@google.com/
Link: https://lkml.kernel.org/r/20210818213304.37038-1-mike.kravetz@oracle.com
Fixes: 846be08578 ("mm/hugetlb: expand restore_reserve_on_error functionality")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: <syzbot+67654e51e54455f1c585@syzkaller.appspotmail.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit 82e5d378b0 ("mm/hugetlb: refactor subpage recording")
refactored the count of subpages but missed an edge case when @vaddr is
not aligned to PAGE_SIZE e.g. when close to vma->vm_end. It would then
errousnly set @refs to 0 and record_subpages_vmas() wouldn't set the
@pages array element to its value, consequently causing the reported
null-deref by syzbot.
Fix it by aligning down @vaddr by PAGE_SIZE in @refs calculation.
Link: https://lkml.kernel.org/r/20210713152440.28650-1-joao.m.martins@oracle.com
Fixes: 82e5d378b0 ("mm/hugetlb: refactor subpage recording")
Reported-by: syzbot+a3fcd59df1b372066f5a@syzkaller.appspotmail.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Both migration and device private pages use special swap entries that are
manipluated by a range of inline functions. The arguments to these are
somewhat inconsistent so rework them to remove flag type arguments and to
make the arguments similar for both read and write entry creation.
Link: https://lkml.kernel.org/r/20210616105937.23201-3-apopple@nvidia.com
Signed-off-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In [1], Jann Horn points out a possible race between
prep_compound_gigantic_page and __page_cache_add_speculative. The root
cause of the possible race is prep_compound_gigantic_page uncondittionally
setting the ref count of pages to zero. It does this because
prep_compound_gigantic_page is handed a 'group' of pages from an allocator
and needs to convert that group of pages to a compound page. The ref
count of each page in this 'group' is one as set by the allocator.
However, the ref count of compound page tail pages must be zero.
The potential race comes about when ref counted pages are returned from
the allocator. When this happens, other mm code could also take a
reference on the page. __page_cache_add_speculative is one such example.
Therefore, prep_compound_gigantic_page can not just set the ref count of
pages to zero as it does today. Doing so would lose the reference taken
by any other code. This would lead to BUGs in code checking ref counts
and could possibly even lead to memory corruption.
There are two possible ways to address this issue.
1) Make all allocators of gigantic groups of pages be able to return a
properly constructed compound page.
2) Make prep_compound_gigantic_page be more careful when constructing a
compound page.
This patch takes approach 2.
In prep_compound_gigantic_page, use cmpxchg to only set ref count to zero
if it is one. If the cmpxchg fails, call synchronize_rcu() in the hope
that the extra ref count will be driopped during a rcu grace period. This
is not a performance critical code path and the wait should be
accceptable. If the ref count is still inflated after the grace period,
then undo any modifications made and return an error.
Currently prep_compound_gigantic_page is type void and does not return
errors. Modify the two callers to check for and handle error returns. On
error, the caller must free the 'group' of pages as they can not be used
to form a gigantic page. After freeing pages, the runtime caller
(alloc_fresh_huge_page) will retry the allocation once. Boot time
allocations can not be retried.
The routine prep_compound_page also unconditionally sets the ref count of
compound page tail pages to zero. However, in this case the buddy
allocator is constructing a compound page from freshly allocated pages.
The ref count on those freshly allocated pages is already zero, so the
set_page_count(p, 0) is unnecessary and could lead to confusion. Just
remove it.
[1] https://lore.kernel.org/linux-mm/CAG48ez23q0Jy9cuVnwAe7t_fdhMk2S7N5Hdi-GLcCeq5bsfLxw@mail.gmail.com/
Link: https://lkml.kernel.org/r/20210622021423.154662-3-mike.kravetz@oracle.com
Fixes: 58a84aa927 ("thp: set compound tail page _count to zero")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Jann Horn <jannh@google.com>
Cc: Youquan Song <youquan.song@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Fix prep_compound_gigantic_page ref count adjustment".
These patches address the possible race between
prep_compound_gigantic_page and __page_cache_add_speculative as described
by Jann Horn in [1].
The first patch simply removes the unnecessary/obsolete helper routine
prep_compound_huge_page to make the actual fix a little simpler.
The second patch is the actual fix and has a detailed explanation in the
commit message.
This potential issue has existed for almost 10 years and I am unaware of
anyone actually hitting the race. I did not cc stable, but would be happy
to squash the patches and send to stable if anyone thinks that is a good
idea.
[1] https://lore.kernel.org/linux-mm/CAG48ez23q0Jy9cuVnwAe7t_fdhMk2S7N5Hdi-GLcCeq5bsfLxw@mail.gmail.com/
This patch (of 2):
I could not think of a reliable way to recreate the issue for testing.
Rather, I 'simulated errors' to exercise all the error paths.
The routine prep_compound_huge_page is a simple wrapper to call either
prep_compound_gigantic_page or prep_compound_page. However, it is only
called from gather_bootmem_prealloc which only processes gigantic pages.
Eliminate the routine and call prep_compound_gigantic_page directly.
Link: https://lkml.kernel.org/r/20210622021423.154662-1-mike.kravetz@oracle.com
Link: https://lkml.kernel.org/r/20210622021423.154662-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Youquan Song <youquan.song@intel.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
On UFFDIO_COPY, if we fail to copy the page contents while holding the
hugetlb_fault_mutex, we will drop the mutex and return to the caller after
allocating a page that consumed a reservation. In this case there may be
a fault that double consumes the reservation. To handle this, we free the
allocated page, fix the reservations, and allocate a temporary hugetlb
page and return that to the caller. When the caller does the copy outside
of the lock, we again check the cache, and allocate a page consuming the
reservation, and copy over the contents.
Test:
Hacked the code locally such that resv_huge_pages underflows produce
a warning and the copy_huge_page_from_user() always fails, then:
./tools/testing/selftests/vm/userfaultfd hugetlb_shared 10
2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success
./tools/testing/selftests/vm/userfaultfd hugetlb 10
2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success
Both tests succeed and produce no warnings. After the
test runs number of free/resv hugepages is correct.
[yuehaibing@huawei.com: remove set but not used variable 'vm_alloc_shared']
Link: https://lkml.kernel.org/r/20210601141610.28332-1-yuehaibing@huawei.com
[almasrymina@google.com: fix allocation error check and copy func name]
Link: https://lkml.kernel.org/r/20210605010626.1459873-1-almasrymina@google.com
Link: https://lkml.kernel.org/r/20210528005029.88088-1-almasrymina@google.com
Signed-off-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Subject: [PATCH v2 0/5] Implement huge VMAP and VMALLOC on powerpc 8xx", v2.
This series implements huge VMAP and VMALLOC on powerpc 8xx.
Powerpc 8xx has 4 page sizes:
- 4k
- 16k
- 512k
- 8M
At the time being, vmalloc and vmap only support huge pages which are
leaf at PMD level.
Here the PMD level is 4M, it doesn't correspond to any supported
page size.
For now, implement use of 16k and 512k pages which is done
at PTE level.
Support of 8M pages will be implemented later, it requires use of
hugepd tables.
To allow this, the architecture provides two functions:
- arch_vmap_pte_range_map_size() which tells vmap_pte_range() what
page size to use. A stub returning PAGE_SIZE is provided when the
architecture doesn't provide this function.
- arch_vmap_pte_supported_shift() which tells __vmalloc_node_range()
what page shift to use for a given area size. A stub returning
PAGE_SHIFT is provided when the architecture doesn't provide this
function.
This patch (of 5):
At the time being, arch_make_huge_pte() has the following prototype:
pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
struct page *page, int writable);
vma is used to get the pages shift or size.
vma is also used on Sparc to get vm_flags.
page is not used.
writable is not used.
In order to use this function without a vma, replace vma by shift and
flags. Also remove the used parameters.
Link: https://lkml.kernel.org/r/cover.1620795204.git.christophe.leroy@csgroup.eu
Link: https://lkml.kernel.org/r/f4633ac6a7da2f22f31a04a89e0a7026bb78b15b.1620795204.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All the infrastructure is ready, so we introduce nr_free_vmemmap_pages
field in the hstate to indicate how many vmemmap pages associated with a
HugeTLB page that can be freed to buddy allocator. And initialize it in
the hugetlb_vmemmap_init(). This patch is actual enablement of the
feature.
There are only (RESERVE_VMEMMAP_SIZE / sizeof(struct page)) struct page
structs that can be used when CONFIG_HUGETLB_PAGE_FREE_VMEMMAP, so add a
BUILD_BUG_ON to catch invalid usage of the tail struct page.
Link: https://lkml.kernel.org/r/20210510030027.56044-10-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Tested-by: Chen Huang <chenhuang5@huawei.com>
Tested-by: Bodeddula Balasubramaniam <bodeddub@amazon.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When we free a HugeTLB page to the buddy allocator, we need to allocate
the vmemmap pages associated with it. However, we may not be able to
allocate the vmemmap pages when the system is under memory pressure. In
this case, we just refuse to free the HugeTLB page. This changes behavior
in some corner cases as listed below:
1) Failing to free a huge page triggered by the user (decrease nr_pages).
User needs to try again later.
2) Failing to free a surplus huge page when freed by the application.
Try again later when freeing a huge page next time.
3) Failing to dissolve a free huge page on ZONE_MOVABLE via
offline_pages().
This can happen when we have plenty of ZONE_MOVABLE memory, but
not enough kernel memory to allocate vmemmmap pages. We may even
be able to migrate huge page contents, but will not be able to
dissolve the source huge page. This will prevent an offline
operation and is unfortunate as memory offlining is expected to
succeed on movable zones. Users that depend on memory hotplug
to succeed for movable zones should carefully consider whether the
memory savings gained from this feature are worth the risk of
possibly not being able to offline memory in certain situations.
4) Failing to dissolve a huge page on CMA/ZONE_MOVABLE via
alloc_contig_range() - once we have that handling in place. Mainly
affects CMA and virtio-mem.
Similar to 3). virito-mem will handle migration errors gracefully.
CMA might be able to fallback on other free areas within the CMA
region.
Vmemmap pages are allocated from the page freeing context. In order for
those allocations to be not disruptive (e.g. trigger oom killer)
__GFP_NORETRY is used. hugetlb_lock is dropped for the allocation because
a non sleeping allocation would be too fragile and it could fail too
easily under memory pressure. GFP_ATOMIC or other modes to access memory
reserves is not used because we want to prevent consuming reserves under
heavy hugetlb freeing.
[mike.kravetz@oracle.com: fix dissolve_free_huge_page use of tail/head page]
Link: https://lkml.kernel.org/r/20210527231225.226987-1-mike.kravetz@oracle.com
[willy@infradead.org: fix alloc_vmemmap_page_list documentation warning]
Link: https://lkml.kernel.org/r/20210615200242.1716568-6-willy@infradead.org
Link: https://lkml.kernel.org/r/20210510030027.56044-7-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Bodeddula Balasubramaniam <bodeddub@amazon.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chen Huang <chenhuang5@huawei.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In the subsequent patch, we should allocate the vmemmap pages when freeing
a HugeTLB page. But update_and_free_page() can be called under any
context, so we cannot use GFP_KERNEL to allocate vmemmap pages. However,
we can defer the actual freeing in a kworker to prevent from using
GFP_ATOMIC to allocate the vmemmap pages.
The __update_and_free_page() is where the call to allocate vmemmmap pages
will be inserted.
Link: https://lkml.kernel.org/r/20210510030027.56044-6-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Bodeddula Balasubramaniam <bodeddub@amazon.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chen Huang <chenhuang5@huawei.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Every HugeTLB has more than one struct page structure. We __know__ that
we only use the first 4 (__NR_USED_SUBPAGE) struct page structures to
store metadata associated with each HugeTLB.
There are a lot of struct page structures associated with each HugeTLB
page. For tail pages, the value of compound_head is the same. So we can
reuse first page of tail page structures. We map the virtual addresses of
the remaining pages of tail page structures to the first tail page struct,
and then free these page frames. Therefore, we need to reserve two pages
as vmemmap areas.
When we allocate a HugeTLB page from the buddy, we can free some vmemmap
pages associated with each HugeTLB page. It is more appropriate to do it
in the prep_new_huge_page().
The free_vmemmap_pages_per_hpage(), which indicates how many vmemmap pages
associated with a HugeTLB page can be freed, returns zero for now, which
means the feature is disabled. We will enable it once all the
infrastructure is there.
[willy@infradead.org: fix documentation warning]
Link: https://lkml.kernel.org/r/20210615200242.1716568-5-willy@infradead.org
Link: https://lkml.kernel.org/r/20210510030027.56044-5-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Tested-by: Chen Huang <chenhuang5@huawei.com>
Tested-by: Bodeddula Balasubramaniam <bodeddub@amazon.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Neukum <oneukum@suse.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__get_hwpoison_page() could fail to grab refcount by some race condition,
so it's helpful if we can handle it by retrying. We already have retry
logic, so make get_hwpoison_page() call get_any_page() when called from
memory_failure().
As a result, get_hwpoison_page() can return negative values (i.e. error
code), so some callers are also changed to handle error cases.
soft_offline_page() does nothing for -EBUSY because that's enough and
users in userspace can easily handle it. unpoison_memory() is also
unchanged because it's broken and need thorough fixes (will be done
later).
Link: https://lkml.kernel.org/r/20210603233632.2964832-3-nao.horiguchi@gmail.com
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If more than one futex is placed on a shmem huge page, it can happen
that waking the second wakes the first instead, and leaves the second
waiting: the key's shared.pgoff is wrong.
When 3.11 commit 13d60f4b6a ("futex: Take hugepages into account when
generating futex_key"), the only shared huge pages came from hugetlbfs,
and the code added to deal with its exceptional page->index was put into
hugetlb source. Then that was missed when 4.8 added shmem huge pages.
page_to_pgoff() is what others use for this nowadays: except that, as
currently written, it gives the right answer on hugetlbfs head, but
nonsense on hugetlbfs tails. Fix that by calling hugetlbfs-specific
hugetlb_basepage_index() on PageHuge tails as well as on head.
Yes, it's unconventional to declare hugetlb_basepage_index() there in
pagemap.h, rather than in hugetlb.h; but I do not expect anything but
page_to_pgoff() ever to need it.
[akpm@linux-foundation.org: give hugetlb_basepage_index() prototype the correct scope]
Link: https://lkml.kernel.org/r/b17d946b-d09-326e-b42a-52884c36df32@google.com
Fixes: 800d8c63b2 ("shmem: add huge pages support")
Reported-by: Neel Natu <neelnatu@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Zhang Yi <wetpzy@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The routine restore_reserve_on_error is called to restore reservation
information when an error occurs after page allocation. The routine
alloc_huge_page modifies the mapping reserve map and potentially the
reserve count during allocation. If code calling alloc_huge_page
encounters an error after allocation and needs to free the page, the
reservation information needs to be adjusted.
Currently, restore_reserve_on_error only takes action on pages for which
the reserve count was adjusted(HPageRestoreReserve flag). There is
nothing wrong with these adjustments. However, alloc_huge_page ALWAYS
modifies the reserve map during allocation even if the reserve count is
not adjusted. This can cause issues as observed during development of
this patch [1].
One specific series of operations causing an issue is:
- Create a shared hugetlb mapping
Reservations for all pages created by default
- Fault in a page in the mapping
Reservation exists so reservation count is decremented
- Punch a hole in the file/mapping at index previously faulted
Reservation and any associated pages will be removed
- Allocate a page to fill the hole
No reservation entry, so reserve count unmodified
Reservation entry added to map by alloc_huge_page
- Error after allocation and before instantiating the page
Reservation entry remains in map
- Allocate a page to fill the hole
Reservation entry exists, so decrement reservation count
This will cause a reservation count underflow as the reservation count
was decremented twice for the same index.
A user would observe a very large number for HugePages_Rsvd in
/proc/meminfo. This would also likely cause subsequent allocations of
hugetlb pages to fail as it would 'appear' that all pages are reserved.
This sequence of operations is unlikely to happen, however they were
easily reproduced and observed using hacked up code as described in [1].
Address the issue by having the routine restore_reserve_on_error take
action on pages where HPageRestoreReserve is not set. In this case, we
need to remove any reserve map entry created by alloc_huge_page. A new
helper routine vma_del_reservation assists with this operation.
There are three callers of alloc_huge_page which do not currently call
restore_reserve_on error before freeing a page on error paths. Add
those missing calls.
[1] https://lore.kernel.org/linux-mm/20210528005029.88088-1-almasrymina@google.com/
Link: https://lkml.kernel.org/r/20210607204510.22617-1-mike.kravetz@oracle.com
Fixes: 96b96a96dd ("mm/hugetlb: fix huge page reservation leak in private mapping error paths"
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When hugetlb page fault (under overcommitting situation) and
memory_failure() race, VM_BUG_ON_PAGE() is triggered by the following
race:
CPU0: CPU1:
gather_surplus_pages()
page = alloc_surplus_huge_page()
memory_failure_hugetlb()
get_hwpoison_page(page)
__get_hwpoison_page(page)
get_page_unless_zero(page)
zero = put_page_testzero(page)
VM_BUG_ON_PAGE(!zero, page)
enqueue_huge_page(h, page)
put_page(page)
__get_hwpoison_page() only checks the page refcount before taking an
additional one for memory error handling, which is not enough because
there's a time window where compound pages have non-zero refcount during
hugetlb page initialization.
So make __get_hwpoison_page() check page status a bit more for hugetlb
pages with get_hwpoison_huge_page(). Checking hugetlb-specific flags
under hugetlb_lock makes sure that the hugetlb page is not transitive.
It's notable that another new function, HWPoisonHandlable(), is helpful
to prevent a race against other transitive page states (like a generic
compound page just before PageHuge becomes true).
Link: https://lkml.kernel.org/r/20210603233632.2964832-2-nao.horiguchi@gmail.com
Fixes: ead07f6a86 ("mm/memory-failure: introduce get_hwpoison_page() for consistent refcount handling")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reported-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: <stable@vger.kernel.org> [5.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The userfaultfd hugetlb tests cause a resv_huge_pages underflow. This
happens when hugetlb_mcopy_atomic_pte() is called with !is_continue on
an index for which we already have a page in the cache. When this
happens, we allocate a second page, double consuming the reservation,
and then fail to insert the page into the cache and return -EEXIST.
To fix this, we first check if there is a page in the cache which
already consumed the reservation, and return -EEXIST immediately if so.
There is still a rare condition where we fail to copy the page contents
AND race with a call for hugetlb_no_page() for this index and again we
will underflow resv_huge_pages. That is fixed in a more complicated
patch not targeted for -stable.
Test:
Hacked the code locally such that resv_huge_pages underflows produce a
warning, then:
./tools/testing/selftests/vm/userfaultfd hugetlb_shared 10
2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success
./tools/testing/selftests/vm/userfaultfd hugetlb 10
2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success
Both tests succeed and produce no warnings. After the test runs number
of free/resv hugepages is correct.
[mike.kravetz@oracle.com: changelog fixes]
Link: https://lkml.kernel.org/r/20210528004649.85298-1-almasrymina@google.com
Fixes: 8fb5debc5f ("userfaultfd: hugetlbfs: add hugetlb_mcopy_atomic_pte for userfaultfd support")
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When memory_failure() or soft_offline_page() is called on a tail page of
some hugetlb page, "BUG: unable to handle page fault" error can be
triggered.
remove_hugetlb_page() dereferences page->lru, so it's assumed that the
page points to a head page, but one of the caller,
dissolve_free_huge_page(), provides remove_hugetlb_page() with 'page'
which could be a tail page. So pass 'head' to it, instead.
Link: https://lkml.kernel.org/r/20210526235257.2769473-1-nao.horiguchi@gmail.com
Fixes: 6eb4e88a6d ("hugetlb: create remove_hugetlb_page() to separate functionality")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When rework early cow of pinned hugetlb pages, we moved huge_ptep_get()
upper but overlooked a side effect that the huge_ptep_get() will fetch the
pte after wr-protection. After moving it upwards, we need explicit
wr-protect of child pte or we will keep the write bit set in the child
process, which could cause data corrution where the child can write to the
original page directly.
This issue can also be exposed by "memfd_test hugetlbfs" kselftest.
Link: https://lkml.kernel.org/r/20210503234356.9097-3-peterx@redhat.com
Fixes: 4eae4efa2c ("hugetlb: do early cow when page pinned on src mm")
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
PF_MEMALLOC_PIN is only honored for CMA pages, extend this flag to work
for any allocations from ZONE_MOVABLE by removing __GFP_MOVABLE from
gfp_mask when this flag is passed in the current context.
Add is_pinnable_page() to return true if page is in a pinnable page. A
pinnable page is not in ZONE_MOVABLE and not of MIGRATE_CMA type.
Link: https://lkml.kernel.org/r/20210215161349.246722-8-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
PF_MEMALLOC_NOCMA is used ot guarantee that the allocator will not
return pages that might belong to CMA region. This is currently used
for long term gup to make sure that such pins are not going to be done
on any CMA pages.
When PF_MEMALLOC_NOCMA has been introduced we haven't realized that it
is focusing on CMA pages too much and that there is larger class of
pages that need the same treatment. MOVABLE zone cannot contain any
long term pins as well so it makes sense to reuse and redefine this flag
for that usecase as well. Rename the flag to PF_MEMALLOC_PIN which
defines an allocation context which can only get pages suitable for
long-term pins.
Also rename: memalloc_nocma_save()/memalloc_nocma_restore to
memalloc_pin_save()/memalloc_pin_restore() and make the new functions
common.
[rppt@linux.ibm.com: fix renaming of PF_MEMALLOC_NOCMA to PF_MEMALLOC_PIN]
Link: https://lkml.kernel.org/r/20210331163816.11517-1-rppt@kernel.org
Link: https://lkml.kernel.org/r/20210215161349.246722-6-pasha.tatashin@soleen.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This ioctl is how userspace ought to resolve "minor" userfaults. The
idea is, userspace is notified that a minor fault has occurred. It
might change the contents of the page using its second non-UFFD mapping,
or not. Then, it calls UFFDIO_CONTINUE to tell the kernel "I have
ensured the page contents are correct, carry on setting up the mapping".
Note that it doesn't make much sense to use UFFDIO_{COPY,ZEROPAGE} for
MINOR registered VMAs. ZEROPAGE maps the VMA to the zero page; but in
the minor fault case, we already have some pre-existing underlying page.
Likewise, UFFDIO_COPY isn't useful if we have a second non-UFFD mapping.
We'd just use memcpy() or similar instead.
It turns out hugetlb_mcopy_atomic_pte() already does very close to what
we want, if an existing page is provided via `struct page **pagep`. We
already special-case the behavior a bit for the UFFDIO_ZEROPAGE case, so
just extend that design: add an enum for the three modes of operation,
and make the small adjustments needed for the MCOPY_ATOMIC_CONTINUE
case. (Basically, look up the existing page, and avoid adding the
existing page to the page cache or calling set_page_huge_active() on
it.)
Link: https://lkml.kernel.org/r/20210301222728.176417-5-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For background, mm/userfaultfd.c provides a general mcopy_atomic
implementation. But some types of memory (i.e., hugetlb and shmem) need
a slightly different implementation, so they provide their own helpers
for this. In other words, userfaultfd is the only caller of these
functions.
This patch achieves two things:
1. Don't spend time compiling code which will end up never being
referenced anyway (a small build time optimization).
2. In patches later in this series, we extend the signature of these
helpers with UFFD-specific state (a mode enumeration). Once this
happens, we *have to* either not compile the helpers, or
unconditionally define the UFFD-only state (which seems messier to me).
This includes the declarations in the headers, as otherwise they'd
yield warnings about implicitly defining the type of those arguments.
Link: https://lkml.kernel.org/r/20210301222728.176417-4-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "userfaultfd: add minor fault handling", v9.
Overview
========
This series adds a new userfaultfd feature, UFFD_FEATURE_MINOR_HUGETLBFS.
When enabled (via the UFFDIO_API ioctl), this feature means that any
hugetlbfs VMAs registered with UFFDIO_REGISTER_MODE_MISSING will *also*
get events for "minor" faults. By "minor" fault, I mean the following
situation:
Let there exist two mappings (i.e., VMAs) to the same page(s) (shared
memory). One of the mappings is registered with userfaultfd (in minor
mode), and the other is not. Via the non-UFFD mapping, the underlying
pages have already been allocated & filled with some contents. The UFFD
mapping has not yet been faulted in; when it is touched for the first
time, this results in what I'm calling a "minor" fault. As a concrete
example, when working with hugetlbfs, we have huge_pte_none(), but
find_lock_page() finds an existing page.
We also add a new ioctl to resolve such faults: UFFDIO_CONTINUE. The idea
is, userspace resolves the fault by either a) doing nothing if the
contents are already correct, or b) updating the underlying contents using
the second, non-UFFD mapping (via memcpy/memset or similar, or something
fancier like RDMA, or etc...). In either case, userspace issues
UFFDIO_CONTINUE to tell the kernel "I have ensured the page contents are
correct, carry on setting up the mapping".
Use Case
========
Consider the use case of VM live migration (e.g. under QEMU/KVM):
1. While a VM is still running, we copy the contents of its memory to a
target machine. The pages are populated on the target by writing to the
non-UFFD mapping, using the setup described above. The VM is still running
(and therefore its memory is likely changing), so this may be repeated
several times, until we decide the target is "up to date enough".
2. We pause the VM on the source, and start executing on the target machine.
During this gap, the VM's user(s) will *see* a pause, so it is desirable to
minimize this window.
3. Between the last time any page was copied from the source to the target, and
when the VM was paused, the contents of that page may have changed - and
therefore the copy we have on the target machine is out of date. Although we
can keep track of which pages are out of date, for VMs with large amounts of
memory, it is "slow" to transfer this information to the target machine. We
want to resume execution before such a transfer would complete.
4. So, the guest begins executing on the target machine. The first time it
touches its memory (via the UFFD-registered mapping), userspace wants to
intercept this fault. Userspace checks whether or not the page is up to date,
and if not, copies the updated page from the source machine, via the non-UFFD
mapping. Finally, whether a copy was performed or not, userspace issues a
UFFDIO_CONTINUE ioctl to tell the kernel "I have ensured the page contents
are correct, carry on setting up the mapping".
We don't have to do all of the final updates on-demand. The userfaultfd manager
can, in the background, also copy over updated pages once it receives the map of
which pages are up-to-date or not.
Interaction with Existing APIs
==============================
Because this is a feature, a registered VMA could potentially receive both
missing and minor faults. I spent some time thinking through how the
existing API interacts with the new feature:
UFFDIO_CONTINUE cannot be used to resolve non-minor faults, as it does not
allocate a new page. If UFFDIO_CONTINUE is used on a non-minor fault:
- For non-shared memory or shmem, -EINVAL is returned.
- For hugetlb, -EFAULT is returned.
UFFDIO_COPY and UFFDIO_ZEROPAGE cannot be used to resolve minor faults.
Without modifications, the existing codepath assumes a new page needs to
be allocated. This is okay, since userspace must have a second
non-UFFD-registered mapping anyway, thus there isn't much reason to want
to use these in any case (just memcpy or memset or similar).
- If UFFDIO_COPY is used on a minor fault, -EEXIST is returned.
- If UFFDIO_ZEROPAGE is used on a minor fault, -EEXIST is returned (or -EINVAL
in the case of hugetlb, as UFFDIO_ZEROPAGE is unsupported in any case).
- UFFDIO_WRITEPROTECT simply doesn't work with shared memory, and returns
-ENOENT in that case (regardless of the kind of fault).
Future Work
===========
This series only supports hugetlbfs. I have a second series in flight to
support shmem as well, extending the functionality. This series is more
mature than the shmem support at this point, and the functionality works
fully on hugetlbfs, so this series can be merged first and then shmem
support will follow.
This patch (of 6):
This feature allows userspace to intercept "minor" faults. By "minor"
faults, I mean the following situation:
Let there exist two mappings (i.e., VMAs) to the same page(s). One of the
mappings is registered with userfaultfd (in minor mode), and the other is
not. Via the non-UFFD mapping, the underlying pages have already been
allocated & filled with some contents. The UFFD mapping has not yet been
faulted in; when it is touched for the first time, this results in what
I'm calling a "minor" fault. As a concrete example, when working with
hugetlbfs, we have huge_pte_none(), but find_lock_page() finds an existing
page.
This commit adds the new registration mode, and sets the relevant flag on
the VMAs being registered. In the hugetlb fault path, if we find that we
have huge_pte_none(), but find_lock_page() does indeed find an existing
page, then we have a "minor" fault, and if the VMA has the userfaultfd
registration flag, we call into userfaultfd to handle it.
This is implemented as a new registration mode, instead of an API feature.
This is because the alternative implementation has significant drawbacks
[1].
However, doing it this was requires we allocate a VM_* flag for the new
registration mode. On 32-bit systems, there are no unused bits, so this
feature is only supported on architectures with
CONFIG_ARCH_USES_HIGH_VMA_FLAGS. When attempting to register a VMA in
MINOR mode on 32-bit architectures, we return -EINVAL.
[1] https://lore.kernel.org/patchwork/patch/1380226/
[peterx@redhat.com: fix minor fault page leak]
Link: https://lkml.kernel.org/r/20210322175132.36659-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20210301222728.176417-1-axelrasmussen@google.com
Link: https://lkml.kernel.org/r/20210301222728.176417-2-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
alloc_contig_range() will fail if it finds a HugeTLB page within the
range, without a chance to handle them. Since HugeTLB pages can be
migrated as any LRU or Movable page, it does not make sense to bail out
without trying. Enable the interface to recognize in-use HugeTLB pages so
we can migrate them, and have much better chances to succeed the call.
Link: https://lkml.kernel.org/r/20210419075413.1064-7-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
alloc_contig_range will fail if it ever sees a HugeTLB page within the
range we are trying to allocate, even when that page is free and can be
easily reallocated.
This has proved to be problematic for some users of alloc_contic_range,
e.g: CMA and virtio-mem, where those would fail the call even when those
pages lay in ZONE_MOVABLE and are free.
We can do better by trying to replace such page.
Free hugepages are tricky to handle so as to no userspace application
notices disruption, we need to replace the current free hugepage with a
new one.
In order to do that, a new function called alloc_and_dissolve_huge_page is
introduced. This function will first try to get a new fresh hugepage, and
if it succeeds, it will replace the old one in the free hugepage pool.
The free page replacement is done under hugetlb_lock, so no external users
of hugetlb will notice the change. To allocate the new huge page, we use
alloc_buddy_huge_page(), so we do not have to deal with any counters, and
prep_new_huge_page() is not called. This is valulable because in case we
need to free the new page, we only need to call __free_pages().
Once we know that the page to be replaced is a genuine 0-refcounted huge
page, we remove the old page from the freelist by remove_hugetlb_page().
Then, we can call __prep_new_huge_page() and
__prep_account_new_huge_page() for the new huge page to properly
initialize it and increment the hstate->nr_huge_pages counter (previously
decremented by remove_hugetlb_page()). Once done, the page is enqueued by
enqueue_huge_page() and it is ready to be used.
There is one tricky case when page's refcount is 0 because it is in the
process of being released. A missing PageHugeFreed bit will tell us that
freeing is in flight so we retry after dropping the hugetlb_lock. The
race window should be small and the next retry should make a forward
progress.
E.g:
CPU0 CPU1
free_huge_page() isolate_or_dissolve_huge_page
PageHuge() == T
alloc_and_dissolve_huge_page
alloc_buddy_huge_page()
spin_lock_irq(hugetlb_lock)
// PageHuge() && !PageHugeFreed &&
// !PageCount()
spin_unlock_irq(hugetlb_lock)
spin_lock_irq(hugetlb_lock)
1) update_and_free_page
PageHuge() == F
__free_pages()
2) enqueue_huge_page
SetPageHugeFreed()
spin_unlock_irq(&hugetlb_lock)
spin_lock_irq(hugetlb_lock)
1) PageHuge() == F (freed by case#1 from CPU0)
2) PageHuge() == T
PageHugeFreed() == T
- proceed with replacing the page
In the case above we retry as the window race is quite small and we have
high chances to succeed next time.
With regard to the allocation, we restrict it to the node the page belongs
to with __GFP_THISNODE, meaning we do not fallback on other node's zones.
Note that gigantic hugetlb pages are fenced off since there is a cyclic
dependency between them and alloc_contig_range.
Link: https://lkml.kernel.org/r/20210419075413.1064-6-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, prep_new_huge_page() performs two functions. It sets the
right state for a new hugetlb, and increases the hstate's counters to
account for the new page.
Let us split its functionality into two separate functions, decoupling
the handling of the counters from initializing a hugepage. The outcome
is having __prep_new_huge_page(), which only initializes the page , and
__prep_account_new_huge_page(), which adds the new page to the hstate's
counters.
This allows us to be able to set a hugetlb without having to worry about
the counter/locking. It will prove useful in the next patch.
prep_new_huge_page() still calls both functions.
Link: https://lkml.kernel.org/r/20210419075413.1064-5-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pages allocated via the page allocator or CMA get its private field
cleared by means of post_alloc_hook().
Pages allocated during boot, that is directly from the memblock
allocator, get cleared by paging_init()-> .. ->memmap_init_zone-> ..
->__init_single_page() before any memblock allocation.
Based on this ground, let us remove the clearing of the flag from
prep_new_huge_page() as it is not needed. This was a leftover from
commit 6c03714901 ("hugetlb: convert PageHugeFreed to HPageFreed
flag").
Previously the explicit clearing was necessary because compound
allocations do not get this initialization (see prep_compound_page).
Link: https://lkml.kernel.org/r/20210419075413.1064-4-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After making hugetlb lock irq safe and separating some functionality
done under the lock, add some lockdep_assert_held to help verify
locking.
Link: https://lkml.kernel.org/r/20210409205254.242291-9-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commit c77c0a8ac4 ("mm/hugetlb: defer freeing of huge pages if in
non-task context") was added to address the issue of free_huge_page being
called from irq context. That commit hands off free_huge_page processing
to a workqueue if !in_task. However, this doesn't cover all the cases as
pointed out by 0day bot lockdep report [1].
: Possible interrupt unsafe locking scenario:
:
: CPU0 CPU1
: ---- ----
: lock(hugetlb_lock);
: local_irq_disable();
: lock(slock-AF_INET);
: lock(hugetlb_lock);
: <Interrupt>
: lock(slock-AF_INET);
Shakeel has later explained that this is very likely TCP TX zerocopy from
hugetlb pages scenario when the networking code drops a last reference to
hugetlb page while having IRQ disabled. Hugetlb freeing path doesn't
disable IRQ while holding hugetlb_lock so a lock dependency chain can lead
to a deadlock.
This commit addresses the issue by doing the following:
- Make hugetlb_lock irq safe. This is mostly a simple process of
changing spin_*lock calls to spin_*lock_irq* calls.
- Make subpool lock irq safe in a similar manner.
- Revert the !in_task check and workqueue handoff.
[1] https://lore.kernel.org/linux-mm/000000000000f1c03b05bc43aadc@google.com/
Link: https://lkml.kernel.org/r/20210409205254.242291-8-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
free_pool_huge_page was called with hugetlb_lock held. It would remove
a hugetlb page, and then free the corresponding pages to the lower level
allocators such as buddy. free_pool_huge_page was called in a loop to
remove hugetlb pages and these loops could hold the hugetlb_lock for a
considerable time.
Create new routine remove_pool_huge_page to replace free_pool_huge_page.
remove_pool_huge_page will remove the hugetlb page, and it must be
called with the hugetlb_lock held. It will return the removed page and
it is the responsibility of the caller to free the page to the lower
level allocators. The hugetlb_lock is dropped before freeing to these
allocators which results in shorter lock hold times.
Add new helper routine to call update_and_free_page for a list of pages.
Note: Some changes to the routine return_unused_surplus_pages are in
need of explanation. Commit e5bbc8a6c9 ("mm/hugetlb.c: fix
reservation race when freeing surplus pages") modified this routine to
address a race which could occur when dropping the hugetlb_lock in the
loop that removes pool pages. Accounting changes introduced in that
commit were subtle and took some thought to understand. This commit
removes the cond_resched_lock() and the potential race. Therefore,
remove the subtle code and restore the more straight forward accounting
effectively reverting the commit.
Link: https://lkml.kernel.org/r/20210409205254.242291-7-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With the introduction of remove_hugetlb_page(), there is no need for
update_and_free_page to hold the hugetlb lock. Change all callers to
drop the lock before calling.
With additional code modifications, this will allow loops which decrease
the huge page pool to drop the hugetlb_lock with each page to reduce
long hold times.
The ugly unlock/lock cycle in free_pool_huge_page will be removed in a
subsequent patch which restructures free_pool_huge_page.
Link: https://lkml.kernel.org/r/20210409205254.242291-6-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The new remove_hugetlb_page() routine is designed to remove a hugetlb
page from hugetlbfs processing. It will remove the page from the active
or free list, update global counters and set the compound page
destructor to NULL so that PageHuge() will return false for the 'page'.
After this call, the 'page' can be treated as a normal compound page or
a collection of base size pages.
update_and_free_page no longer decrements h->nr_huge_pages{_node} as
this is performed in remove_hugetlb_page. The only functionality
performed by update_and_free_page is to free the base pages to the lower
level allocators.
update_and_free_page is typically called after remove_hugetlb_page.
remove_hugetlb_page is to be called with the hugetlb_lock held.
Creating this routine and separating functionality is in preparation for
restructuring code to reduce lock hold times. This commit should not
introduce any changes to functionality.
Link: https://lkml.kernel.org/r/20210409205254.242291-5-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The helper routine hstate_next_node_to_alloc accesses and modifies the
hstate variable next_nid_to_alloc. The helper is used by the routines
alloc_pool_huge_page and adjust_pool_surplus. adjust_pool_surplus is
called with hugetlb_lock held. However, alloc_pool_huge_page can not be
called with the hugetlb lock held as it will call the page allocator.
Two instances of alloc_pool_huge_page could be run in parallel or
alloc_pool_huge_page could run in parallel with adjust_pool_surplus
which may result in the variable next_nid_to_alloc becoming invalid for
the caller and pages being allocated on the wrong node.
Both alloc_pool_huge_page and adjust_pool_surplus are only called from
the routine set_max_huge_pages after boot. set_max_huge_pages is only
called as the reusult of a user writing to the proc/sysfs nr_hugepages,
or nr_hugepages_mempolicy file to adjust the number of hugetlb pages.
It makes little sense to allow multiple adjustment to the number of
hugetlb pages in parallel. Add a mutex to the hstate and use it to only
allow one hugetlb page adjustment at a time. This will synchronize
modifications to the next_nid_to_alloc variable.
Link: https://lkml.kernel.org/r/20210409205254.242291-4-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Now that cma_release is non-blocking and irq safe, there is no need to
drop hugetlb_lock before calling.
Link: https://lkml.kernel.org/r/20210409205254.242291-3-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: HORIGUCHI NAOYA <naoya.horiguchi@nec.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A rare out of memory error would prevent removal of the reserve map region
for a page. hugetlb_fix_reserve_counts() handles this rare case to avoid
dangling with incorrect counts. Unfortunately, hugepage_subpool_get_pages
and hugetlb_acct_memory could possibly fail too. We should correctly
handle these cases.
Link: https://lkml.kernel.org/r/20210410072348.20437-5-linmiaohe@huawei.com
Fixes: b5cec28d36 ("hugetlbfs: truncate_hugepages() takes a range of pages")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Feilong Lin <linfeilong@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The resv_map could be NULL since this routine can be called in the evict
inode path for all hugetlbfs inodes and we will have chg = 0 in this case.
But (chg - freed) won't go negative as Mike pointed out:
"If resv_map is NULL, then no hugetlb pages can be allocated/associated
with the file. As a result, remove_inode_hugepages will never find any
huge pages associated with the inode and the passed value 'freed' will
always be zero."
Add a comment clarifying this to make it clear and also avoid confusion.
Link: https://lkml.kernel.org/r/20210410072348.20437-4-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Feilong Lin <linfeilong@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It's guaranteed that the vma is associated with a resv_map, i.e. either
VM_MAYSHARE or HPAGE_RESV_OWNER, when the code reaches here or we would
have returned via !resv check above. So it's unneeded to check whether
HPAGE_RESV_OWNER is set here. Simplify the return code to make it more
clear.
Link: https://lkml.kernel.org/r/20210410072348.20437-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Feilong Lin <linfeilong@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Cleanup and fixup for hugetlb", v2.
This series contains cleanups to remove redundant VM_BUG_ON() and simplify
the return code. Also this handles the error case in
hugetlb_fix_reserve_counts() correctly. More details can be found in the
respective changelogs.
This patch (of 5):
The same VM_BUG_ON() check is already done in the callee. Remove this
extra one to simplify the code slightly.
Link: https://lkml.kernel.org/r/20210410072348.20437-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210410072348.20437-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Feilong Lin <linfeilong@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Rework the error handling code when alloc_huge_page() failed to remove
some duplicated code and simplify the code slightly.
Link: https://lkml.kernel.org/r/20210308112809.26107-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We should not transfer the per-node surplus state when we do not cross the
node in order to save some cpu cycles
Link: https://lkml.kernel.org/r/20210308112809.26107-3-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Some cleanups for hugetlb".
This series contains cleanups to remove unnecessary VM_BUG_ON_PAGE, use
helper function and so on. I also collect some previous patches into this
series in case they are forgotten.
This patch (of 5):
We could use pages_per_huge_page to get the number of pages per hugepage,
use get_hstate_idx to calculate hstate index, and use hstate_is_gigantic
to check if a hstate is gigantic to make code more succinct.
Link: https://lkml.kernel.org/r/20210308112809.26107-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210308112809.26107-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
vma_resv_map(vma) checks if a reserve map is associated with the vma.
The routine vma_needs_reservation() will check vma_resv_map(vma) and
return 1 if no reserv map is present. map_chg is set to the return
value of vma_needs_reservation(). Therefore, !vma_resv_map(vma) is
redundant in the expression:
map_chg || avoid_reserve || !vma_resv_map(vma);
Remove the redundant check.
[Thanks Mike Kravetz for reshaping this commit message!]
Link: https://lkml.kernel.org/r/20210301104726.45159-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Huge pmd sharing for hugetlbfs is racy with userfaultfd-wp because
userfaultfd-wp is always based on pgtable entries, so they cannot be
shared.
Walk the hugetlb range and unshare all such mappings if there is, right
before UFFDIO_REGISTER will succeed and return to userspace.
This will pair with want_pmd_share() in hugetlb code so that huge pmd
sharing is completely disabled for userfaultfd-wp registered range.
Link: https://lkml.kernel.org/r/20210218231206.15524-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Huge pmd sharing could bring problem to userfaultfd. The thing is that
userfaultfd is running its logic based on the special bits on page table
entries, however the huge pmd sharing could potentially share page table
entries for different address ranges. That could cause issues on
either:
- When sharing huge pmd page tables for an uffd write protected range,
the newly mapped huge pmd range will also be write protected
unexpectedly, or,
- When we try to write protect a range of huge pmd shared range, we'll
first do huge_pmd_unshare() in hugetlb_change_protection(), however
that also means the UFFDIO_WRITEPROTECT could be silently skipped for
the shared region, which could lead to data loss.
While at it, a few other things are done altogether:
- Move want_pmd_share() from mm/hugetlb.c into linux/hugetlb.h, because
that's definitely something that arch code would like to use too
- ARM64 currently directly check against
CONFIG_ARCH_WANT_HUGE_PMD_SHARE when trying to share huge pmd. Switch
to the want_pmd_share() helper.
- Move vma_shareable() from huge_pmd_share() into want_pmd_share().
[peterx@redhat.com: fix build with !ARCH_WANT_HUGE_PMD_SHARE]
Link: https://lkml.kernel.org/r/20210310185359.88297-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20210218231202.15426-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "hugetlb: Disable huge pmd unshare for uffd-wp", v4.
This series tries to disable huge pmd unshare of hugetlbfs backed memory
for uffd-wp. Although uffd-wp of hugetlbfs is still during rfc stage,
the idea of this series may be needed for multiple tasks (Axel's uffd
minor fault series, and Mike's soft dirty series), so I picked it out
from the larger series.
This patch (of 4):
It is a preparation work to be able to behave differently in the per
architecture huge_pte_alloc() according to different VMA attributes.
Pass it deeper into huge_pmd_share() so that we can avoid the find_vma() call.
[peterx@redhat.com: build fix]
Link: https://lkml.kernel.org/r/20210304164653.GB397383@xz-x1Link: https://lkml.kernel.org/r/20210218230633.15028-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20210218230633.15028-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Adam Ruprecht <ruprecht@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Cannon Matthews <cannonmatthews@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: David Rientjes <rientjes@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: "Michal Koutn" <mkoutny@suse.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shawn Anastasio <shawn@anastas.io>
Cc: Steven Price <steven.price@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There are only two callers of __alloc_pages() so prune the thicket of
alloc_page variants by combining the two functions together. Current
callers of __alloc_pages() simply add an extra 'NULL' parameter and
current callers of __alloc_pages_nodemask() call __alloc_pages() instead.
Link: https://lkml.kernel.org/r/20210225150642.2582252-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current implementation of hugetlb_cgroup for shared mappings could
have different behavior. Consider the following two scenarios:
1.Assume initial css reference count of hugetlb_cgroup is 1:
1.1 Call hugetlb_reserve_pages with from = 1, to = 2. So css reference
count is 2 associated with 1 file_region.
1.2 Call hugetlb_reserve_pages with from = 2, to = 3. So css reference
count is 3 associated with 2 file_region.
1.3 coalesce_file_region will coalesce these two file_regions into
one. So css reference count is 3 associated with 1 file_region
now.
2.Assume initial css reference count of hugetlb_cgroup is 1 again:
2.1 Call hugetlb_reserve_pages with from = 1, to = 3. So css reference
count is 2 associated with 1 file_region.
Therefore, we might have one file_region while holding one or more css
reference counts. This inconsistency could lead to imbalanced css_get()
and css_put() pair. If we do css_put one by one (i.g. hole punch case),
scenario 2 would put one more css reference. If we do css_put all
together (i.g. truncate case), scenario 1 will leak one css reference.
The imbalanced css_get() and css_put() pair would result in a non-zero
reference when we try to destroy the hugetlb cgroup. The hugetlb cgroup
directory is removed __but__ associated resource is not freed. This
might result in OOM or can not create a new hugetlb cgroup in a busy
workload ultimately.
In order to fix this, we have to make sure that one file_region must
hold exactly one css reference. So in coalesce_file_region case, we
should release one css reference before coalescence. Also only put css
reference when the entire file_region is removed.
The last thing to note is that the caller of region_add() will only hold
one reference to h_cg->css for the whole contiguous reservation region.
But this area might be scattered when there are already some
file_regions reside in it. As a result, many file_regions may share only
one h_cg->css reference. In order to ensure that one file_region must
hold exactly one css reference, we should do css_get() for each
file_region and release the reference held by caller when they are done.
[linmiaohe@huawei.com: fix imbalanced css_get and css_put pair for shared mappings]
Link: https://lkml.kernel.org/r/20210316023002.53921-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210301120540.37076-1-linmiaohe@huawei.com
Fixes: 075a61d07a ("hugetlb_cgroup: add accounting for shared mappings")
Reported-by: kernel test robot <lkp@intel.com> (auto build test ERROR)
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Wanpeng Li <liwp.linux@gmail.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is the last missing piece of the COW-during-fork effort when there're
pinned pages found. One can reference 70e806e4e6 ("mm: Do early cow for
pinned pages during fork() for ptes", 2020-09-27) for more information,
since we do similar things here rather than pte this time, but just for
hugetlb.
Note that after Jason's recent work on 57efa1fe59 ("mm/gup: prevent
gup_fast from racing with COW during fork", 2020-12-15) which is safer and
easier to understand, we're safe now within the whole copy_page_range()
against gup-fast, we don't need the wr-protect trick that proposed in
70e806e4e6 anymore.
Link: https://lkml.kernel.org/r/20210217233547.93892-6-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Gal Pressman <galpress@amazon.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Wei Zhang <wzam@amazon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
After is_cow_mapping() is exported in mm.h, replace some manual checks
elsewhere throughout the tree but start to use the new helper.
Link: https://lkml.kernel.org/r/20210217233547.93892-5-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@ziepe.ca>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Gal Pressman <galpress@amazon.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Wei Zhang <wzam@amazon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All the regions maintained in hugetlb reserved map is inclusive on "from"
but exclusive on "to". We can break earlier even if rg->from==t because
it already means no possible intersection.
This does not need a Fixes in all cases because when it happens
(rg->from==t) we'll not break out of the loop while we should, however the
next thing we'd do is still add the last file_region we'd need and quit
the loop in the next round. So this change is not a bugfix (since the old
code should still run okay iiuc), but we'd better still touch it up to
make it logically sane.
Link: https://lkml.kernel.org/r/20210217233547.93892-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Gal Pressman <galpress@amazon.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Cc: Wei Zhang <wzam@amazon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm/hugetlb: Early cow on fork, and a few cleanups", v5.
As reported by Gal [1], we still miss the code clip to handle early cow
for hugetlb case, which is true. Again, it still feels odd to fork()
after using a few huge pages, especially if they're privately mapped to
me.. However I do agree with Gal and Jason in that we should still have
that since that'll complete the early cow on fork effort at least, and
it'll still fix issues where buffers are not well under control and not
easy to apply MADV_DONTFORK.
The first two patches (1-2) are some cleanups I noticed when reading into
the hugetlb reserve map code. I think it's good to have but they're not
necessary for fixing the fork issue.
The last two patches (3-4) are the real fix.
I tested this with a fork() after some vfio-pci assignment, so I'm pretty
sure the page copy path could trigger well (page will be accounted right
after the fork()), but I didn't do data check since the card I assigned is
some random nic.
https://github.com/xzpeter/linux/tree/fork-cow-pin-huge
[1] https://lore.kernel.org/lkml/27564187-4a08-f187-5a84-3df50009f6ca@amazon.com/
Introduce hugetlb_resv_map_add() helper to add a new file_region rather
than duplication the similar code twice in add_reservation_in_range().
Link: https://lkml.kernel.org/r/20210217233547.93892-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20210217233547.93892-2-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Gal Pressman <galpress@amazon.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Wei Zhang <wzam@amazon.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jann Horn <jannh@google.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: Roland Scheidegger <sroland@vmware.com>
Cc: VMware Graphics <linux-graphics-maintainer@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
While reviewing a bug in hugetlb_reserve_pages, it was noticed that all
callers ignore the return value. Any failure is considered an ENOMEM
error by the callers.
Change the function to be of type bool. The function will return true if
the reservation was successful, false otherwise. Callers currently assume
a zero return code indicates success. Change the callers to look for true
to indicate success. No functional change, only code cleanup.
Link: https://lkml.kernel.org/r/20201221192542.15732-1-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Gerald Schaefer reported a panic on s390 in hugepage_subpool_put_pages()
with linux-next 5.12.0-20210222.
Call trace:
hugepage_subpool_put_pages.part.0+0x2c/0x138
__free_huge_page+0xce/0x310
alloc_pool_huge_page+0x102/0x120
set_max_huge_pages+0x13e/0x350
hugetlb_sysctl_handler_common+0xd8/0x110
hugetlb_sysctl_handler+0x48/0x58
proc_sys_call_handler+0x138/0x238
new_sync_write+0x10e/0x198
vfs_write.part.0+0x12c/0x238
ksys_write+0x68/0xf8
do_syscall+0x82/0xd0
__do_syscall+0xb4/0xc8
system_call+0x72/0x98
This is a result of the change which moved the hugetlb page subpool
pointer from page->private to page[1]->private. When new pages are
allocated from the buddy allocator, the private field of the head
page will be cleared, but the private field of subpages is not modified.
Therefore, old values may remain.
Fix by initializing hugetlb page subpool pointer in prep_new_huge_page().
Link: https://lkml.kernel.org/r/20210223215544.313871-1-mike.kravetz@oracle.com
Fixes: f1280272ae4d ("hugetlb: use page.private for hugetlb specific page flags")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use new hugetlb specific HPageFreed flag to replace the PageHugeFreed
interfaces.
Link: https://lkml.kernel.org/r/20210122195231.324857-6-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use new hugetlb specific HPageTemporary flag to replace the
PageHugeTemporary() interfaces. PageHugeTemporary does contain a
PageHuge() check. However, this interface is only used within hugetlb
code where we know we are dealing with a hugetlb page. Therefore, the
check can be eliminated.
Link: https://lkml.kernel.org/r/20210122195231.324857-5-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use the new hugetlb page specific flag HPageMigratable to replace the
page_huge_active interfaces. By it's name, page_huge_active implied that
a huge page was on the active list. However, that is not really what code
checking the flag wanted to know. It really wanted to determine if the
huge page could be migrated. This happens when the page is actually added
to the page cache and/or task page table. This is the reasoning behind
the name change.
The VM_BUG_ON_PAGE() calls in the *_huge_active() interfaces are not
really necessary as we KNOW the page is a hugetlb page. Therefore, they
are removed.
The routine page_huge_active checked for PageHeadHuge before testing the
active bit. This is unnecessary in the case where we hold a reference or
lock and know it is a hugetlb head page. page_huge_active is also called
without holding a reference or lock (scan_movable_pages), and can race
with code freeing the page. The extra check in page_huge_active shortened
the race window, but did not prevent the race. Offline code calling
scan_movable_pages already deals with these races, so removing the check
is acceptable. Add comment to racy code.
[songmuchun@bytedance.com: remove set_page_huge_active() declaration from include/linux/hugetlb.h]
Link: https://lkml.kernel.org/r/CAMZfGtUda+KoAZscU0718TN61cSFwp4zy=y2oZ=+6Z2TAZZwng@mail.gmail.com
Link: https://lkml.kernel.org/r/20210122195231.324857-3-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "create hugetlb flags to consolidate state", v3.
While discussing a series of hugetlb fixes in [1], it became evident that
the hugetlb specific page state information is stored in a somewhat
haphazard manner. Code dealing with state information would be easier to
read, understand and maintain if this information was stored in a
consistent manner.
This series uses page.private of the hugetlb head page for storing a set
of hugetlb specific page flags. Routines are priovided for test, set and
clear of the flags.
[1] https://lore.kernel.org/r/20210106084739.63318-1-songmuchun@bytedance.com
This patch (of 4):
As hugetlbfs evolved, state information about hugetlb pages was added.
One 'convenient' way of doing this was to use available fields in tail
pages. Over time, it has become difficult to know the meaning or contents
of fields simply by looking at a small bit of code. Sometimes, the naming
is just confusing. For example: The PagePrivate flag indicates a huge
page reservation was consumed and needs to be restored if an error is
encountered and the page is freed before it is instantiated. The
page.private field contains the pointer to a subpool if the page is
associated with one.
In an effort to make the code more readable, use page.private to contain
hugetlb specific page flags. These flags will have test, set and clear
functions similar to those used for 'normal' page flags. More
importantly, an enum of flag values will be created with names that
actually reflect their purpose.
In this patch,
- Create infrastructure for hugetlb specific page flag functions
- Move subpool pointer to page[1].private to make way for flags
Create routines with meaningful names to modify subpool field
- Use new HPageRestoreReserve flag instead of PagePrivate
Conversion of other state information will happen in subsequent patches.
Link: https://lkml.kernel.org/r/20210122195231.324857-1-mike.kravetz@oracle.com
Link: https://lkml.kernel.org/r/20210122195231.324857-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If hugetlb_cma is enabled, it will skip boot time allocation when
allocating gigantic page, that doesn't means allocation failure, so
suppress this warning info.
Link: https://lkml.kernel.org/r/20210219123909.13130-1-chenwandun@huawei.com
Fixes: cf11e85fc0 ("mm: hugetlb: optionally allocate gigantic hugepages using cma")
Signed-off-by: Chen Wandun <chenwandun@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
page structs are not guaranteed to be contiguous for gigantic pages. The
routine update_and_free_page can encounter a gigantic page, yet it assumes
page structs are contiguous when setting page flags in subpages.
If update_and_free_page encounters non-contiguous page structs, we can see
“BUG: Bad page state in process …” errors.
Non-contiguous page structs are generally not an issue. However, they can
exist with a specific kernel configuration and hotplug operations. For
example: Configure the kernel with CONFIG_SPARSEMEM and
!CONFIG_SPARSEMEM_VMEMMAP. Then, hotplug add memory for the area where
the gigantic page will be allocated. Zi Yan outlined steps to reproduce
here [1].
[1] https://lore.kernel.org/linux-mm/16F7C58B-4D79-41C5-9B64-A1A1628F4AF2@nvidia.com/
Link: https://lkml.kernel.org/r/20210217184926.33567-1-mike.kravetz@oracle.com
Fixes: 944d9fec8d ("hugetlb: add support for gigantic page allocation at runtime")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We can use helper huge_page_size() to get the hugepage size directly to
simplify the code slightly.
[linmiaohe@huawei.com: use helper huge_page_size() to get hugepage size]
Link: https://lkml.kernel.org/r/20210209021803.49211-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210208082450.15716-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All callers know they are operating on a hugetlb head page. So this
VM_BUG_ON_PAGE can not catch anything useful.
Link: https://lkml.kernel.org/r/20210209071151.44731-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We could use helper function range_in_vma() to check whether the vma is in
the desired range to simplify the code.
Link: https://lkml.kernel.org/r/20210204112949.43051-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Gigantic page is a compound page and its order is more than 1. Thus it
must be available for hpage_pincount. Let's remove the redundant check
for gigantic page.
Link: https://lkml.kernel.org/r/20210202112002.73170-1-yanfei.xu@windriver.com
Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix typos sasitfy to satisfy, reservtion to reservation, hugegpage to
hugepage and uniprocesor to uniprocessor in comments.
Link: https://lkml.kernel.org/r/20210128112028.64831-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
For a given hugepage backing a VA, there's a rather ineficient loop which
is solely responsible for storing subpages in GUP @pages/@vmas array. For
each subpage we check whether it's within range or size of @pages and keep
increment @pfn_offset and a couple other variables per subpage iteration.
Simplify this logic and minimize the cost of each iteration to just store
the output page/vma. Instead of incrementing number of @refs iteratively,
we do it through pre-calculation of @refs and only with a tight loop for
storing pinned subpages/vmas.
Additionally, retain existing behaviour with using mem_map_offset() when
recording the subpages for configurations that don't have a contiguous
mem_map.
pinning consequently improves bringing us close to
{pin,get}_user_pages_fast:
- 16G with 1G huge page size
gup_test -f /mnt/huge/file -m 16384 -r 30 -L -S -n 512 -w
PIN_LONGTERM_BENCHMARK: ~12.8k us -> ~5.8k us
PIN_FAST_BENCHMARK: ~3.7k us
Link: https://lkml.kernel.org/r/20210128182632.24562-3-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm/hugetlb: follow_hugetlb_page() improvements", v2.
While looking at ZONE_DEVICE struct page reuse particularly the last
patch[0], I found two possible improvements for follow_hugetlb_page()
which is solely used for get_user_pages()/pin_user_pages().
The first patch batches page refcount updates while the second tidies up
storing the subpages/vmas. Both together bring the cost of slow variant
of gup() cost from ~87.6k usecs to ~5.8k usecs.
libhugetlbfs tests seem to pass as well gup_test benchmarks with hugetlbfs
vmas.
This patch (of 2):
follow_hugetlb_page() once it locks the pmd/pud, checks all its N subpages
in a huge page and grabs a reference for each one. Similar to gup-fast,
have follow_hugetlb_page() grab the head page refcount only after counting
all its subpages that are part of the just faulted huge page.
Consequently we reduce the number of atomics necessary to pin said huge
page, which improves non-fast gup() considerably:
- 16G with 1G huge page size
gup_test -f /mnt/huge/file -m 16384 -r 10 -L -S -n 512 -w
PIN_LONGTERM_BENCHMARK: ~87.6k us -> ~12.8k us
Link: https://lkml.kernel.org/r/20210128182632.24562-1-joao.m.martins@oracle.com
Link: https://lkml.kernel.org/r/20210128182632.24562-2-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix the following coccicheck warnings:
mm/hugetlb.c:3372:20-22: WARNING !A || A && B is equivalent to !A || B.
Link: https://lkml.kernel.org/r/1611643468-52233-1-git-send-email-abaci-bugfix@linux.alibaba.com
Signed-off-by: Jiapeng Zhong <abaci-bugfix@linux.alibaba.com>
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a hugetlbfs filesystem is created with the min_size option and
without the size option, used_hpages is always 0 and might lead to
release subpool prematurely because it indicates no pages are used now
while there might be.
In order to fix this issue, we should check used_hpages == 0 iff
max_hpages accounting is enabled. As max_hpages accounting should be
enabled in most common case, this is not worth a Cc stable.
[mike.kravetz@oracle.com: new changelog]
Link: https://lkml.kernel.org/r/20210126115510.53374-1-linmiaohe@huawei.com
Signed-off-by: Hongxiang Lou <louhongxiang@huawei.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit a551643895 ("hugetlb: modular state for hugetlb page
size"), we can use huge_page_order to access hstate->order and
pages_per_huge_page to fetch the pages per huge page. But
gather_bootmem_prealloc() forgot to use it.
Link: https://lkml.kernel.org/r/20210114114435.40075-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When reservation accounting remains unchanged, hugetlb_acct_memory() will
do nothing except holding and releasing hugetlb_lock. We should avoid
this unnecessary hugetlb_lock lock/unlock cycle which is happening on
'most' hugetlb munmap operations by check delta against 0 at the beginning
of hugetlb_acct_memory.
Link: https://lkml.kernel.org/r/20210115092013.61012-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The current code would unnecessarily expand the address range. Consider
one example, (start, end) = (1G-2M, 3G+2M), and (vm_start, vm_end) =
(1G-4M, 3G+4M), the expected adjustment should be keep (1G-2M, 3G+2M)
without expand. But the current result will be (1G-4M, 3G+4M). Actually,
the range (1G-4M, 1G) and (3G, 3G+4M) would never been involved in pmd
sharing.
After this patch, we will check that the vma span at least one PUD aligned
size and the start,end range overlap the aligned range of vma.
With above example, the aligned vma range is (1G, 3G), so if (start, end)
range is within (1G-4M, 1G), or within (3G, 3G+4M), then no adjustment to
both start and end. Otherwise, we will have chance to adjust start
downwards or end upwards without exceeding (vm_start, vm_end).
Mike:
: The 'adjusted range' is used for calls to mmu notifiers and cache(tlb)
: flushing. Since the current code unnecessarily expands the range in some
: cases, more entries than necessary would be flushed. This would/could
: result in performance degradation. However, this is highly dependent on
: the user runtime. Is there a combination of vma layout and calls to
: actually hit this issue? If the issue is hit, will those entries
: unnecessarily flushed be used again and need to be unnecessarily reloaded?
Link: https://lkml.kernel.org/r/20210104081631.2921415-1-lixinhai.lxh@gmail.com
Fixes: 75802ca663 ("mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible")
Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In hugetlb_sysfs_add_hstate(), we would do kobject_put() on hstate_kobjs
when failed to create sysfs group but forget to set hstate_kobjs to NULL.
Then in hugetlb_register_node() error path, we may free it again via
hugetlb_unregister_node().
Link: https://lkml.kernel.org/r/20210107123249.36964-1-linmiaohe@huawei.com
Fixes: a343787016 ("hugetlb: new sysfs interface")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <smuchun@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The VM_BUG_ON_PAGE avoids the generation of any code, even if that
expression has side-effects when !CONFIG_DEBUG_VM.
Link: https://lkml.kernel.org/r/20210126031009.96266-1-songmuchun@bytedance.com
Fixes: e5dfacebe4 ("mm/hugetlb.c: just use put_page_testzero() instead of page_count()")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The page_huge_active() can be called from scan_movable_pages() which do
not hold a reference count to the HugeTLB page. So when we call
page_huge_active() from scan_movable_pages(), the HugeTLB page can be
freed parallel. Then we will trigger a BUG_ON which is in the
page_huge_active() when CONFIG_DEBUG_VM is enabled. Just remove the
VM_BUG_ON_PAGE.
Link: https://lkml.kernel.org/r/20210115124942.46403-6-songmuchun@bytedance.com
Fixes: 7e1f049efb ("mm: hugetlb: cleanup using paeg_huge_active()")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a race between isolate_huge_page() and __free_huge_page().
CPU0: CPU1:
if (PageHuge(page))
put_page(page)
__free_huge_page(page)
spin_lock(&hugetlb_lock)
update_and_free_page(page)
set_compound_page_dtor(page,
NULL_COMPOUND_DTOR)
spin_unlock(&hugetlb_lock)
isolate_huge_page(page)
// trigger BUG_ON
VM_BUG_ON_PAGE(!PageHead(page), page)
spin_lock(&hugetlb_lock)
page_huge_active(page)
// trigger BUG_ON
VM_BUG_ON_PAGE(!PageHuge(page), page)
spin_unlock(&hugetlb_lock)
When we isolate a HugeTLB page on CPU0. Meanwhile, we free it to the
buddy allocator on CPU1. Then, we can trigger a BUG_ON on CPU0, because
it is already freed to the buddy allocator.
Link: https://lkml.kernel.org/r/20210115124942.46403-5-songmuchun@bytedance.com
Fixes: c8721bbbdd ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
There is a race condition between __free_huge_page()
and dissolve_free_huge_page().
CPU0: CPU1:
// page_count(page) == 1
put_page(page)
__free_huge_page(page)
dissolve_free_huge_page(page)
spin_lock(&hugetlb_lock)
// PageHuge(page) && !page_count(page)
update_and_free_page(page)
// page is freed to the buddy
spin_unlock(&hugetlb_lock)
spin_lock(&hugetlb_lock)
clear_page_huge_active(page)
enqueue_huge_page(page)
// It is wrong, the page is already freed
spin_unlock(&hugetlb_lock)
The race window is between put_page() and dissolve_free_huge_page().
We should make sure that the page is already on the free list when it is
dissolved.
As a result __free_huge_page would corrupt page(s) already in the buddy
allocator.
Link: https://lkml.kernel.org/r/20210115124942.46403-4-songmuchun@bytedance.com
Fixes: c8721bbbdd ("mm: memory-hotplug: enable memory hotplug to handle hugepage")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a new hugetlb page is allocated during fallocate it will not be
marked as active (set_page_huge_active) which will result in a later
isolate_huge_page failure when the page migration code would like to
move that page. Such a failure would be unexpected and wrong.
Only export set_page_huge_active, just leave clear_page_huge_active as
static. Because there are no external users.
Link: https://lkml.kernel.org/r/20210115124942.46403-3-songmuchun@bytedance.com
Fixes: 70c3547e36 (hugetlbfs: add hugetlbfs_fallocate())
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The 'start' and 'end' arguments to tlb_gather_mmu() are no longer
needed now that there is a separate function for 'fullmm' flushing.
Remove the unused arguments and update all callers.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/CAHk-=wjQWa14_4UpfDf=fiineNP+RH74kZeDMo_f1D35xNzq9w@mail.gmail.com
Since commit 7a30df49f6 ("mm: mmu_gather: remove __tlb_reset_range()
for force flush"), the 'start' and 'end' arguments to tlb_finish_mmu()
are no longer used, since we flush the whole mm in case of a nested
invalidation.
Remove the unused arguments and update all callers.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Yu Zhao <yuzhao@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20210127235347.1402-3-will@kernel.org
The huge page size is encoded for VM_FAULT_HWPOISON errors only. So if
we return VM_FAULT_HWPOISON, huge page size would just be ignored.
Link: https://lkml.kernel.org/r/20210107123449.38481-1-linmiaohe@huawei.com
Fixes: aa50d3a7aa ("Encode huge page size for VM_FAULT_HWPOISON errors")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Baolin Wang