Merge updates from Andrew Morton:
"A large amount of MM, plenty more to come.
Subsystems affected by this patch series:
- tools
- kthread
- kbuild
- scripts
- ocfs2
- vfs
- mm: slub, kmemleak, pagecache, gup, swap, memcg, pagemap, mremap,
sparsemem, kasan, pagealloc, vmscan, compaction, mempolicy,
hugetlbfs, hugetlb"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (155 commits)
include/linux/huge_mm.h: check PageTail in hpage_nr_pages even when !THP
mm/hugetlb: fix build failure with HUGETLB_PAGE but not HUGEBTLBFS
selftests/vm: fix map_hugetlb length used for testing read and write
mm/hugetlb: remove unnecessary memory fetch in PageHeadHuge()
mm/hugetlb.c: clean code by removing unnecessary initialization
hugetlb_cgroup: add hugetlb_cgroup reservation docs
hugetlb_cgroup: add hugetlb_cgroup reservation tests
hugetlb: support file_region coalescing again
hugetlb_cgroup: support noreserve mappings
hugetlb_cgroup: add accounting for shared mappings
hugetlb: disable region_add file_region coalescing
hugetlb_cgroup: add reservation accounting for private mappings
mm/hugetlb_cgroup: fix hugetlb_cgroup migration
hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations
hugetlb_cgroup: add hugetlb_cgroup reservation counter
hugetlbfs: Use i_mmap_rwsem to address page fault/truncate race
hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization
mm/memblock.c: remove redundant assignment to variable max_addr
mm: mempolicy: require at least one nodeid for MPOL_PREFERRED
mm: mempolicy: use VM_BUG_ON_VMA in queue_pages_test_walk()
...
Patch series "hugetlbfs: use i_mmap_rwsem for more synchronization", v2.
While discussing the issue with huge_pte_offset [1], I remembered that
there were more outstanding hugetlb races. These issues are:
1) For shared pmds, huge PTE pointers returned by huge_pte_alloc can become
invalid via a call to huge_pmd_unshare by another thread.
2) hugetlbfs page faults can race with truncation causing invalid global
reserve counts and state.
A previous attempt was made to use i_mmap_rwsem in this manner as
described at [2]. However, those patches were reverted starting with [3]
due to locking issues.
To effectively use i_mmap_rwsem to address the above issues it needs to be
held (in read mode) during page fault processing. However, during fault
processing we need to lock the page we will be adding. Lock ordering
requires we take page lock before i_mmap_rwsem. Waiting until after
taking the page lock is too late in the fault process for the
synchronization we want to do.
To address this lock ordering issue, the following patches change the lock
ordering for hugetlb pages. This is not too invasive as hugetlbfs
processing is done separate from core mm in many places. However, I don't
really like this idea. Much ugliness is contained in the new routine
hugetlb_page_mapping_lock_write() of patch 1.
The only other way I can think of to address these issues is by catching
all the races. After catching a race, cleanup, backout, retry ... etc,
as needed. This can get really ugly, especially for huge page
reservations. At one time, I started writing some of the reservation
backout code for page faults and it got so ugly and complicated I went
down the path of adding synchronization to avoid the races. Any other
suggestions would be welcome.
[1] https://lore.kernel.org/linux-mm/1582342427-230392-1-git-send-email-longpeng2@huawei.com/
[2] https://lore.kernel.org/linux-mm/20181222223013.22193-1-mike.kravetz@oracle.com/
[3] https://lore.kernel.org/linux-mm/20190103235452.29335-1-mike.kravetz@oracle.com
[4] https://lore.kernel.org/linux-mm/1584028670.7365.182.camel@lca.pw/
[5] https://lore.kernel.org/lkml/20200312183142.108df9ac@canb.auug.org.au/
This patch (of 2):
While looking at BUGs associated with invalid huge page map counts, it was
discovered and observed that a huge pte pointer could become 'invalid' and
point to another task's page table. Consider the following:
A task takes a page fault on a shared hugetlbfs file and calls
huge_pte_alloc to get a ptep. Suppose the returned ptep points to a
shared pmd.
Now, another task truncates the hugetlbfs file. As part of truncation, it
unmaps everyone who has the file mapped. If the range being truncated is
covered by a shared pmd, huge_pmd_unshare will be called. For all but the
last user of the shared pmd, huge_pmd_unshare will clear the pud pointing
to the pmd. If the task in the middle of the page fault is not the last
user, the ptep returned by huge_pte_alloc now points to another task's
page table or worse. This leads to bad things such as incorrect page
map/reference counts or invalid memory references.
To fix, expand the use of i_mmap_rwsem as follows:
- i_mmap_rwsem is held in read mode whenever huge_pmd_share is called.
huge_pmd_share is only called via huge_pte_alloc, so callers of
huge_pte_alloc take i_mmap_rwsem before calling. In addition, callers
of huge_pte_alloc continue to hold the semaphore until finished with
the ptep.
- i_mmap_rwsem is held in write mode whenever huge_pmd_unshare is called.
One problem with this scheme is that it requires taking i_mmap_rwsem
before taking the page lock during page faults. This is not the order
specified in the rest of mm code. Handling of hugetlbfs pages is mostly
isolated today. Therefore, we use this alternative locking order for
PageHuge() pages.
mapping->i_mmap_rwsem
hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
page->flags PG_locked (lock_page)
To help with lock ordering issues, hugetlb_page_mapping_lock_write() is
introduced to write lock the i_mmap_rwsem associated with a page.
In most cases it is easy to get address_space via vma->vm_file->f_mapping.
However, in the case of migration or memory errors for anon pages we do
not have an associated vma. A new routine _get_hugetlb_page_mapping()
will use anon_vma to get address_space in these cases.
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Link: http://lkml.kernel.org/r/20200316205756.146666-2-mike.kravetz@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add a new src_owner field to struct migrate_vma. If the field is set,
only device private pages with page->pgmap->owner equal to that field are
migrated. If the field is not set only "normal" pages are migrated.
Fixes: df6ad69838 ("mm/device-public-memory: device memory cache coherent with CPU")
Link: https://lore.kernel.org/r/20200316193216.920734-3-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Tested-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
The pte_hole() callback is called at multiple levels of the page tables.
Code dumping the kernel page tables needs to know what at what depth the
missing entry is. Add this is an extra parameter to pte_hole(). When the
depth isn't know (e.g. processing a vma) then -1 is passed.
The depth that is reported is the actual level where the entry is missing
(ignoring any folding that is in place), i.e. any levels where
PTRS_PER_P?D is set to 1 are ignored.
Note that depth starts at 0 for a PGD so that PUD/PMD/PTE retain their
natural numbers as levels 2/3/4.
Link: http://lkml.kernel.org/r/20191218162402.45610-16-steven.price@arm.com
Signed-off-by: Steven Price <steven.price@arm.com>
Tested-by: Zong Li <zong.li@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.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>
migrate_vma_insert_page() closely follows the code in:
__handle_mm_fault()
handle_pte_fault()
do_anonymous_page()
Add a call to check_stable_address_space() after locking the page table
entry before inserting a ZONE_DEVICE private zero page mapping similar
to page faulting a new anonymous page.
Link: http://lkml.kernel.org/r/20200107211208.24595-4-rcampbell@nvidia.com
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Chris Down <chris@chrisdown.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix some comment typos and coding style clean up in preparation for the
next patch. No functional changes.
Link: http://lkml.kernel.org/r/20200107211208.24595-3-rcampbell@nvidia.com
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Acked-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Bharata B Rao <bharata@linux.ibm.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>
Addresses passed to walk_page_range() callback functions are already
page aligned and don't need to be masked with PAGE_MASK.
Link: http://lkml.kernel.org/r/20200107211208.24595-2-rcampbell@nvidia.com
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Chris Down <chris@chrisdown.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit a49bd4d716 ("mm, numa: rework do_pages_move"), the
semantic of move_pages() has changed to return the number of
non-migrated pages if they were result of a non-fatal reasons (usually a
busy page).
This was an unintentional change that hasn't been noticed except for LTP
tests which checked for the documented behavior.
There are two ways to go around this change. We can even get back to
the original behavior and return -EAGAIN whenever migrate_pages is not
able to migrate pages due to non-fatal reasons. Another option would be
to simply continue with the changed semantic and extend move_pages
documentation to clarify that -errno is returned on an invalid input or
when migration simply cannot succeed (e.g. -ENOMEM, -EBUSY) or the
number of pages that couldn't have been migrated due to ephemeral
reasons (e.g. page is pinned or locked for other reasons).
This patch implements the second option because this behavior is in
place for some time without anybody complaining and possibly new users
depending on it. Also it allows to have a slightly easier error
handling as the caller knows that it is worth to retry when err > 0.
But since the new semantic would be aborted immediately if migration is
failed due to ephemeral reasons, need include the number of
non-attempted pages in the return value too.
Link: http://lkml.kernel.org/r/1580160527-109104-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: a49bd4d716 ("mm, numa: rework do_pages_move")
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Wei Yang <richardw.yang@linux.intel.com>
Cc: <stable@vger.kernel.org> [4.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If we get here after successfully adding page to list, err would be 1 to
indicate the page is queued in the list.
Current code has two problems:
* on success, 0 is not returned
* on error, if add_page_for_migratioin() return 1, and the following err1
from do_move_pages_to_node() is set, the err1 is not returned since err
is 1
And these behaviors break the user interface.
Link: http://lkml.kernel.org/r/20200119065753.21694-1-richardw.yang@linux.intel.com
Fixes: e0153fc2c7 ("mm: move_pages: return valid node id in status if the page is already on the target node").
Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Lameter <cl@linux.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Felix Abecassis reports move_pages() would return random status if the
pages are already on the target node by the below test program:
int main(void)
{
const long node_id = 1;
const long page_size = sysconf(_SC_PAGESIZE);
const int64_t num_pages = 8;
unsigned long nodemask = 1 << node_id;
long ret = set_mempolicy(MPOL_BIND, &nodemask, sizeof(nodemask));
if (ret < 0)
return (EXIT_FAILURE);
void **pages = malloc(sizeof(void*) * num_pages);
for (int i = 0; i < num_pages; ++i) {
pages[i] = mmap(NULL, page_size, PROT_WRITE | PROT_READ,
MAP_PRIVATE | MAP_POPULATE | MAP_ANONYMOUS,
-1, 0);
if (pages[i] == MAP_FAILED)
return (EXIT_FAILURE);
}
ret = set_mempolicy(MPOL_DEFAULT, NULL, 0);
if (ret < 0)
return (EXIT_FAILURE);
int *nodes = malloc(sizeof(int) * num_pages);
int *status = malloc(sizeof(int) * num_pages);
for (int i = 0; i < num_pages; ++i) {
nodes[i] = node_id;
status[i] = 0xd0; /* simulate garbage values */
}
ret = move_pages(0, num_pages, pages, nodes, status, MPOL_MF_MOVE);
printf("move_pages: %ld\n", ret);
for (int i = 0; i < num_pages; ++i)
printf("status[%d] = %d\n", i, status[i]);
}
Then running the program would return nonsense status values:
$ ./move_pages_bug
move_pages: 0
status[0] = 208
status[1] = 208
status[2] = 208
status[3] = 208
status[4] = 208
status[5] = 208
status[6] = 208
status[7] = 208
This is because the status is not set if the page is already on the
target node, but move_pages() should return valid status as long as it
succeeds. The valid status may be errno or node id.
We can't simply initialize status array to zero since the pages may be
not on node 0. Fix it by updating status with node id which the page is
already on.
Link: http://lkml.kernel.org/r/1575584353-125392-1-git-send-email-yang.shi@linux.alibaba.com
Fixes: a49bd4d716 ("mm, numa: rework do_pages_move")
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reported-by: Felix Abecassis <fabecassis@nvidia.com>
Tested-by: Felix Abecassis <fabecassis@nvidia.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: <stable@vger.kernel.org> [4.17+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When zone_watermark_ok() is called in migrate_balanced_pgdat() to check
migration target node, the parameter classzone_idx (for requested zone)
is specified as 0 (ZONE_DMA). But when allocating memory for autonuma
in alloc_misplaced_dst_page(), the requested zone from GFP flags is
ZONE_MOVABLE. That is, the requested zone is different. The size of
lowmem_reserve for the different requested zone is different. And this
may cause some issues.
For example, in the zoneinfo of a test machine as below,
Node 0, zone DMA32
pages free 61592
min 29
low 454
high 879
spanned 1044480
present 442306
managed 425921
protection: (0, 0, 62457, 62457, 62457)
The free page number of ZONE_DMA32 is greater than "high watermark +
lowmem_reserve[ZONE_DMA]", but less than "high watermark +
lowmem_reserve[ZONE_MOVABLE]". And because __alloc_pages_node() in
alloc_misplaced_dst_page() requests ZONE_MOVABLE, the
zone_watermark_ok() on ZONE_DMA32 in migrate_balanced_pgdat() may always
return true. So, autonuma may not stop even when memory pressure in
node 0 is heavy.
To fix the issue, ZONE_MOVABLE is used as parameter to call
zone_watermark_ok() in migrate_balanced_pgdat(). This makes it same as
requested zone in alloc_misplaced_dst_page(). So that
migrate_balanced_pgdat() returns false when memory pressure is heavy.
Link: http://lkml.kernel.org/r/20191101075727.26683-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When doing migration if the freed page is met, we just return without
migrating it since it is pointless to migrate a freed page. But, the
current code allocates target page unconditionally before handling freed
page, if the page is freed, the newly allocated will be just freed. It
doesn't make too much sense and is just a waste of time although
migrating freed page is rare.
So, handle freed page at the before that to avoid unnecessary page
allocation and free.
Link: http://lkml.kernel.org/r/1573755869-106954-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
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 patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.
This patch allows tagged pointers to be passed to the following memory
syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect,
mremap, msync, munlock, move_pages.
The mmap and mremap syscalls do not currently accept tagged addresses.
Architectures may interpret the tag as a background colour for the
corresponding vma.
Link: http://lkml.kernel.org/r/aaf0c0969d46b2feb9017f3e1b3ef3970b633d91.1563904656.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Eric Auger <eric.auger@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jens Wiklander <jens.wiklander@linaro.org>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Mike Rapoport <rppt@linux.ibm.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>
Transparent Huge Pages are currently stored in i_pages as pointers to
consecutive subpages. This patch changes that to storing consecutive
pointers to the head page in preparation for storing huge pages more
efficiently in i_pages.
Large parts of this are "inspired" by Kirill's patch
https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@linux.intel.com/
Kirill and Huang Ying contributed several fixes.
[willy@infradead.org: use compound_nr, squish uninit-var warning]
Link: http://lkml.kernel.org/r/20190731210400.7419-1-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Jan Kara <jack@suse.cz>
Reviewed-by: Kirill Shutemov <kirill@shutemov.name>
Reviewed-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Tested-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Tested-by: Qian Cai <cai@lca.pw>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Song Liu <songliubraving@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Replace 1 << compound_order(page) with compound_nr(page). Minor
improvements in readability.
Link: http://lkml.kernel.org/r/20190721104612.19120-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The mm_walk structure currently mixed data and code. Split out the
operations vectors into a new mm_walk_ops structure, and while we are
changing the API also declare the mm_walk structure inside the
walk_page_range and walk_page_vma functions.
Based on patch from Linus Torvalds.
Link: https://lore.kernel.org/r/20190828141955.22210-3-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Add a new header for the two handful of users of the walk_page_range /
walk_page_vma interface instead of polluting all users of mm.h with it.
Link: https://lore.kernel.org/r/20190828141955.22210-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
From rdma.git
Jason Gunthorpe says:
====================
This is a collection of general cleanups for ODP to clarify some of the
flows around umem creation and use of the interval tree.
====================
The branch is based on v5.3-rc5 due to dependencies, and is being taken
into hmm.git due to dependencies in the next patches.
* odp_fixes:
RDMA/mlx5: Use odp instead of mr->umem in pagefault_mr
RDMA/mlx5: Use ib_umem_start instead of umem.address
RDMA/core: Make invalidate_range a device operation
RDMA/odp: Use kvcalloc for the dma_list and page_list
RDMA/odp: Check for overflow when computing the umem_odp end
RDMA/odp: Provide ib_umem_odp_release() to undo the allocs
RDMA/odp: Split creating a umem_odp from ib_umem_get
RDMA/odp: Make the three ways to create a umem_odp clear
RMDA/odp: Consolidate umem_odp initialization
RDMA/odp: Make it clearer when a umem is an implicit ODP umem
RDMA/odp: Iterate over the whole rbtree directly
RDMA/odp: Use the common interval tree library instead of generic
RDMA/mlx5: Fix MR npages calculation for IB_ACCESS_HUGETLB
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
CONFIG_MIGRATE_VMA_HELPER guards helpers that are required for proper
devic private memory support. Remove the option and just check for
CONFIG_DEVICE_PRIVATE instead.
Link: https://lore.kernel.org/r/20190814075928.23766-11-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
No one ever checks this flag, and we could easily get that information
from the page if needed.
Link: https://lore.kernel.org/r/20190814075928.23766-10-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
There isn't any good reason to pass callbacks to migrate_vma. Instead
we can just export the three steps done by this function to drivers and
let them sequence the operation without callbacks. This removes a lot
of boilerplate code as-is, and will allow the drivers to drastically
improve code flow and error handling further on.
Link: https://lore.kernel.org/r/20190814075928.23766-2-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Tested-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
When CONFIG_MIGRATE_VMA_HELPER is enabled, migrate_vma() calls
migrate_vma_collect() which initializes a struct mm_walk but didn't
initialize mm_walk.pud_entry. (Found by code inspection) Use a C
structure initialization to make sure it is set to NULL.
Link: http://lkml.kernel.org/r/20190719233225.12243-1-rcampbell@nvidia.com
Fixes: 8763cb45ab ("mm/migrate: new memory migration helper for use with device memory")
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
buffer_migrate_page_norefs() can race with bh users in the following
way:
CPU1 CPU2
buffer_migrate_page_norefs()
buffer_migrate_lock_buffers()
checks bh refs
spin_unlock(&mapping->private_lock)
__find_get_block()
spin_lock(&mapping->private_lock)
grab bh ref
spin_unlock(&mapping->private_lock)
move page do bh work
This can result in various issues like lost updates to buffers (i.e.
metadata corruption) or use after free issues for the old page.
This patch closes the race by holding mapping->private_lock while the
mapping is being moved to a new page. Ordinarily, a reference can be
taken outside of the private_lock using the per-cpu BH LRU but the
references are checked and the LRU invalidated if necessary. The
private_lock is held once the references are known so the buffer lookup
slow path will spin on the private_lock. Between the page lock and
private_lock, it should be impossible for other references to be
acquired and updates to happen during the migration.
A user had reported data corruption issues on a distribution kernel with
a similar page migration implementation as mainline. The data
corruption could not be reproduced with this patch applied. A small
number of migration-intensive tests were run and no performance problems
were noted.
[mgorman@techsingularity.net: Changelog, removed tracing]
Link: http://lkml.kernel.org/r/20190718090238.GF24383@techsingularity.net
Fixes: 89cb0888ca "mm: migrate: provide buffer_migrate_page_norefs()"
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Cc: <stable@vger.kernel.org> [5.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
migrate_page_move_mapping() doesn't use the mode argument. Remove it
and update callers accordingly.
Link: http://lkml.kernel.org/r/20190508210301.8472-1-keith.busch@intel.com
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Improvements and bug fixes for the hmm interface in the kernel:
- Improve clarity, locking and APIs related to the 'hmm mirror' feature
merged last cycle. In linux-next we now see AMDGPU and nouveau to be
using this API.
- Remove old or transitional hmm APIs. These are hold overs from the past
with no users, or APIs that existed only to manage cross tree conflicts.
There are still a few more of these cleanups that didn't make the merge
window cut off.
- Improve some core mm APIs:
* export alloc_pages_vma() for driver use
* refactor into devm_request_free_mem_region() to manage
DEVICE_PRIVATE resource reservations
* refactor duplicative driver code into the core dev_pagemap
struct
- Remove hmm wrappers of improved core mm APIs, instead have drivers use
the simplified API directly
- Remove DEVICE_PUBLIC
- Simplify the kconfig flow for the hmm users and core code
-----BEGIN PGP SIGNATURE-----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=wKvp
-----END PGP SIGNATURE-----
Merge tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma
Pull HMM updates from Jason Gunthorpe:
"Improvements and bug fixes for the hmm interface in the kernel:
- Improve clarity, locking and APIs related to the 'hmm mirror'
feature merged last cycle. In linux-next we now see AMDGPU and
nouveau to be using this API.
- Remove old or transitional hmm APIs. These are hold overs from the
past with no users, or APIs that existed only to manage cross tree
conflicts. There are still a few more of these cleanups that didn't
make the merge window cut off.
- Improve some core mm APIs:
- export alloc_pages_vma() for driver use
- refactor into devm_request_free_mem_region() to manage
DEVICE_PRIVATE resource reservations
- refactor duplicative driver code into the core dev_pagemap
struct
- Remove hmm wrappers of improved core mm APIs, instead have drivers
use the simplified API directly
- Remove DEVICE_PUBLIC
- Simplify the kconfig flow for the hmm users and core code"
* tag 'for-linus-hmm' of git://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma: (42 commits)
mm: don't select MIGRATE_VMA_HELPER from HMM_MIRROR
mm: remove the HMM config option
mm: sort out the DEVICE_PRIVATE Kconfig mess
mm: simplify ZONE_DEVICE page private data
mm: remove hmm_devmem_add
mm: remove hmm_vma_alloc_locked_page
nouveau: use devm_memremap_pages directly
nouveau: use alloc_page_vma directly
PCI/P2PDMA: use the dev_pagemap internal refcount
device-dax: use the dev_pagemap internal refcount
memremap: provide an optional internal refcount in struct dev_pagemap
memremap: replace the altmap_valid field with a PGMAP_ALTMAP_VALID flag
memremap: remove the data field in struct dev_pagemap
memremap: add a migrate_to_ram method to struct dev_pagemap_ops
memremap: lift the devmap_enable manipulation into devm_memremap_pages
memremap: pass a struct dev_pagemap to ->kill and ->cleanup
memremap: move dev_pagemap callbacks into a separate structure
memremap: validate the pagemap type passed to devm_memremap_pages
mm: factor out a devm_request_free_mem_region helper
mm: export alloc_pages_vma
...
The code hasn't been used since it was added to the tree, and doesn't
appear to actually be usable.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This updates each existing invalidation to use the correct mmu notifier
event that represent what is happening to the CPU page table. See the
patch which introduced the events to see the rational behind this.
Link: http://lkml.kernel.org/r/20190326164747.24405-7-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
CPU page table update can happens for many reasons, not only as a result
of a syscall (munmap(), mprotect(), mremap(), madvise(), ...) but also as
a result of kernel activities (memory compression, reclaim, migration,
...).
Users of mmu notifier API track changes to the CPU page table and take
specific action for them. While current API only provide range of virtual
address affected by the change, not why the changes is happening.
This patchset do the initial mechanical convertion of all the places that
calls mmu_notifier_range_init to also provide the default MMU_NOTIFY_UNMAP
event as well as the vma if it is know (most invalidation happens against
a given vma). Passing down the vma allows the users of mmu notifier to
inspect the new vma page protection.
The MMU_NOTIFY_UNMAP is always the safe default as users of mmu notifier
should assume that every for the range is going away when that event
happens. A latter patch do convert mm call path to use a more appropriate
events for each call.
This is done as 2 patches so that no call site is forgotten especialy
as it uses this following coccinelle patch:
%<----------------------------------------------------------------------
@@
identifier I1, I2, I3, I4;
@@
static inline void mmu_notifier_range_init(struct mmu_notifier_range *I1,
+enum mmu_notifier_event event,
+unsigned flags,
+struct vm_area_struct *vma,
struct mm_struct *I2, unsigned long I3, unsigned long I4) { ... }
@@
@@
-#define mmu_notifier_range_init(range, mm, start, end)
+#define mmu_notifier_range_init(range, event, flags, vma, mm, start, end)
@@
expression E1, E3, E4;
identifier I1;
@@
<...
mmu_notifier_range_init(E1,
+MMU_NOTIFY_UNMAP, 0, I1,
I1->vm_mm, E3, E4)
...>
@@
expression E1, E2, E3, E4;
identifier FN, VMA;
@@
FN(..., struct vm_area_struct *VMA, ...) {
<...
mmu_notifier_range_init(E1,
+MMU_NOTIFY_UNMAP, 0, VMA,
E2, E3, E4)
...> }
@@
expression E1, E2, E3, E4;
identifier FN, VMA;
@@
FN(...) {
struct vm_area_struct *VMA;
<...
mmu_notifier_range_init(E1,
+MMU_NOTIFY_UNMAP, 0, VMA,
E2, E3, E4)
...> }
@@
expression E1, E2, E3, E4;
identifier FN;
@@
FN(...) {
<...
mmu_notifier_range_init(E1,
+MMU_NOTIFY_UNMAP, 0, NULL,
E2, E3, E4)
...> }
---------------------------------------------------------------------->%
Applied with:
spatch --all-includes --sp-file mmu-notifier.spatch fs/proc/task_mmu.c --in-place
spatch --sp-file mmu-notifier.spatch --dir kernel/events/ --in-place
spatch --sp-file mmu-notifier.spatch --dir mm --in-place
Link: http://lkml.kernel.org/r/20190326164747.24405-6-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Felix Kuehling <Felix.Kuehling@amd.com>
Cc: Jason Gunthorpe <jgg@mellanox.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Transparent Huge Pages are currently stored in i_pages as pointers to
consecutive subpages. This patch changes that to storing consecutive
pointers to the head page in preparation for storing huge pages more
efficiently in i_pages.
Large parts of this are "inspired" by Kirill's patch
https://lore.kernel.org/lkml/20170126115819.58875-2-kirill.shutemov@linux.intel.com/
[willy@infradead.org: fix swapcache pages]
Link: http://lkml.kernel.org/r/20190324155441.GF10344@bombadil.infradead.org
[kirill@shutemov.name: hugetlb stores pages in page cache differently]
Link: http://lkml.kernel.org/r/20190404134553.vuvhgmghlkiw2hgl@kshutemo-mobl1
Link: http://lkml.kernel.org/r/20190307153051.18815-1-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Jan Kara <jack@suse.cz>
Reviewed-by: Kirill Shutemov <kirill@shutemov.name>
Reviewed-and-tested-by: Song Liu <songliubraving@fb.com>
Tested-by: William Kucharski <william.kucharski@oracle.com>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Tested-by: Qian Cai <cai@lca.pw>
Cc: Hugh Dickins <hughd@google.com>
Cc: Song Liu <liu.song.a23@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Our MIPS 1004Kc SoCs were seeing random userspace crashes with SIGILL
and SIGSEGV that could not be traced back to a userspace code bug. They
had all the magic signs of an I/D cache coherency issue.
Now recently we noticed that the /proc/sys/vm/compact_memory interface
was quite efficient at provoking this class of userspace crashes.
Studying the code in mm/migrate.c there is a distinction made between
migrating a page that is mapped at the instant of migration and one that
is not mapped. Our problem turned out to be the non-mapped pages.
For the non-mapped page the code performs a copy of the page content and
all relevant meta-data of the page without doing the required D-cache
maintenance. This leaves dirty data in the D-cache of the CPU and on
the 1004K cores this data is not visible to the I-cache. A subsequent
page-fault that triggers a mapping of the page will happily serve the
process with potentially stale code.
What about ARM then, this bug should have seen greater exposure? Well
ARM became immune to this flaw back in 2010, see commit c01778001a
("ARM: 6379/1: Assume new page cache pages have dirty D-cache").
My proposed fix moves the D-cache maintenance inside move_to_new_page to
make it common for both cases.
Link: http://lkml.kernel.org/r/20190315083502.11849-1-larper@axis.com
Fixes: 97ee052461 ("flush cache before installing new page at migraton")
Signed-off-by: Lars Persson <larper@axis.com>
Reviewed-by: Paul Burton <paul.burton@mips.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrea has noted that page migration code propagates page_mapping(page)
through the whole migration stack down to migrate_page() function so it
seems stupid to then use page_mapping(page) in expected_page_refs()
instead of passed down 'mapping' argument. I agree so let's make
expected_page_refs() more in line with the rest of the migration stack.
Link: http://lkml.kernel.org/r/20190207112314.24872-1-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Suggested-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
No functional change.
Link: http://lkml.kernel.org/r/20190118235123.27843-1-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pages with no migration handler use a fallback handler which sometimes
works and sometimes persistently retries. A historical example was
blockdev pages but there are others such as odd refcounting when
page->private is used. These are retried multiple times which is
wasteful during compaction so this patch will fail migration faster
unless the caller specifies MIGRATE_SYNC.
This is not expected to help THP allocation success rates but it did
reduce latencies very slightly in some cases.
1-socket thpfioscale
4.20.0 4.20.0
noreserved-v2r15 failfast-v2r15
Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
Amean fault-both-3 3839.67 ( 0.00%) 3833.72 ( 0.15%)
Amean fault-both-5 5177.47 ( 0.00%) 4967.15 ( 4.06%)
Amean fault-both-7 7245.03 ( 0.00%) 7139.19 ( 1.46%)
Amean fault-both-12 11534.89 ( 0.00%) 11326.30 ( 1.81%)
Amean fault-both-18 16241.10 ( 0.00%) 16270.70 ( -0.18%)
Amean fault-both-24 19075.91 ( 0.00%) 19839.65 ( -4.00%)
Amean fault-both-30 22712.11 ( 0.00%) 21707.05 ( 4.43%)
Amean fault-both-32 21692.92 ( 0.00%) 21968.16 ( -1.27%)
The 2-socket results are not materially different. Scan rates are
similar as expected.
Link: http://lkml.kernel.org/r/20190118175136.31341-7-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Rientjes <rientjes@google.com>
Cc: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "arm64/mm: Enable HugeTLB migration", v4.
This patch series enables HugeTLB migration support for all supported
huge page sizes at all levels including contiguous bit implementation.
Following HugeTLB migration support matrix has been enabled with this
patch series. All permutations have been tested except for the 16GB.
CONT PTE PMD CONT PMD PUD
-------- --- -------- ---
4K: 64K 2M 32M 1G
16K: 2M 32M 1G
64K: 2M 512M 16G
First the series adds migration support for PUD based huge pages. It
then adds a platform specific hook to query an architecture if a given
huge page size is supported for migration while also providing a default
fallback option preserving the existing semantics which just checks for
(PMD|PUD|PGDIR)_SHIFT macros. The last two patches enables HugeTLB
migration on arm64 and subscribe to this new platform specific hook by
defining an override.
The second patch differentiates between movability and migratability
aspects of huge pages and implements hugepage_movable_supported() which
can then be used during allocation to decide whether to place the huge
page in movable zone or not.
This patch (of 5):
During huge page allocation it's migratability is checked to determine
if it should be placed under movable zones with GFP_HIGHUSER_MOVABLE.
But the movability aspect of the huge page could depend on other factors
than just migratability. Movability in itself is a distinct property
which should not be tied with migratability alone.
This differentiates these two and implements an enhanced movability check
which also considers huge page size to determine if it is feasible to be
placed under a movable zone. At present it just checks for gigantic pages
but going forward it can incorporate other enhanced checks.
Link: http://lkml.kernel.org/r/1545121450-1663-2-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hugetlb pages should only be migrated if they are 'active'. The
routines set/clear_page_huge_active() modify the active state of hugetlb
pages.
When a new hugetlb page is allocated at fault time, set_page_huge_active
is called before the page is locked. Therefore, another thread could
race and migrate the page while it is being added to page table by the
fault code. This race is somewhat hard to trigger, but can be seen by
strategically adding udelay to simulate worst case scheduling behavior.
Depending on 'how' the code races, various BUG()s could be triggered.
To address this issue, simply delay the set_page_huge_active call until
after the page is successfully added to the page table.
Hugetlb pages can also be leaked at migration time if the pages are
associated with a file in an explicitly mounted hugetlbfs filesystem.
For example, consider a two node system with 4GB worth of huge pages
available. A program mmaps a 2G file in a hugetlbfs filesystem. It
then migrates the pages associated with the file from one node to
another. When the program exits, huge page counts are as follows:
node0
1024 free_hugepages
1024 nr_hugepages
node1
0 free_hugepages
1024 nr_hugepages
Filesystem Size Used Avail Use% Mounted on
nodev 4.0G 2.0G 2.0G 50% /var/opt/hugepool
That is as expected. 2G of huge pages are taken from the free_hugepages
counts, and 2G is the size of the file in the explicitly mounted
filesystem. If the file is then removed, the counts become:
node0
1024 free_hugepages
1024 nr_hugepages
node1
1024 free_hugepages
1024 nr_hugepages
Filesystem Size Used Avail Use% Mounted on
nodev 4.0G 2.0G 2.0G 50% /var/opt/hugepool
Note that the filesystem still shows 2G of pages used, while there
actually are no huge pages in use. The only way to 'fix' the filesystem
accounting is to unmount the filesystem
If a hugetlb page is associated with an explicitly mounted filesystem,
this information in contained in the page_private field. At migration
time, this information is not preserved. To fix, simply transfer
page_private from old to new page at migration time if necessary.
There is a related race with removing a huge page from a file and
migration. When a huge page is removed from the pagecache, the
page_mapping() field is cleared, yet page_private remains set until the
page is actually freed by free_huge_page(). A page could be migrated
while in this state. However, since page_mapping() is not set the
hugetlbfs specific routine to transfer page_private is not called and we
leak the page count in the filesystem.
To fix that, check for this condition before migrating a huge page. If
the condition is detected, return EBUSY for the page.
Link: http://lkml.kernel.org/r/74510272-7319-7372-9ea6-ec914734c179@oracle.com
Link: http://lkml.kernel.org/r/20190212221400.3512-1-mike.kravetz@oracle.com
Fixes: bcc5422230 ("mm: hugetlb: introduce page_huge_active")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: <stable@vger.kernel.org>
[mike.kravetz@oracle.com: v2]
Link: http://lkml.kernel.org/r/7534d322-d782-8ac6-1c8d-a8dc380eb3ab@oracle.com
[mike.kravetz@oracle.com: update comment and changelog]
Link: http://lkml.kernel.org/r/420bcfd6-158b-38e4-98da-26d0cd85bd01@oracle.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We had a race in the old balloon compaction code before b1123ea6d3
("mm: balloon: use general non-lru movable page feature") refactored it
that became visible after backporting 195a8c43e9 ("virtio-balloon:
deflate via a page list") without the refactoring.
The bug existed from commit d6d86c0a7f ("mm/balloon_compaction:
redesign ballooned pages management") till b1123ea6d3 ("mm: balloon:
use general non-lru movable page feature"). d6d86c0a7f
("mm/balloon_compaction: redesign ballooned pages management") was
backported to 3.12, so the broken kernels are stable kernels [3.12 -
4.7].
There was a subtle race between dropping the page lock of the newpage in
__unmap_and_move() and checking for __is_movable_balloon_page(newpage).
Just after dropping this page lock, virtio-balloon could go ahead and
deflate the newpage, effectively dequeueing it and clearing PageBalloon,
in turn making __is_movable_balloon_page(newpage) fail.
This resulted in dropping the reference of the newpage via
putback_lru_page(newpage) instead of put_page(newpage), leading to
page->lru getting modified and a !LRU page ending up in the LRU lists.
With 195a8c43e9 ("virtio-balloon: deflate via a page list")
backported, one would suddenly get corrupted lists in
release_pages_balloon():
- WARNING: CPU: 13 PID: 6586 at lib/list_debug.c:59 __list_del_entry+0xa1/0xd0
- list_del corruption. prev->next should be ffffe253961090a0, but was dead000000000100
Nowadays this race is no longer possible, but it is hidden behind very
ugly handling of __ClearPageMovable() and __PageMovable().
__ClearPageMovable() will not make __PageMovable() fail, only
PageMovable(). So the new check (__PageMovable(newpage)) will still
hold even after newpage was dequeued by virtio-balloon.
If anybody would ever change that special handling, the BUG would be
introduced again. So instead, make it explicit and use the information
of the original isolated page before migration.
This patch can be backported fairly easy to stable kernels (in contrast
to the refactoring).
Link: http://lkml.kernel.org/r/20190129233217.10747-1-david@redhat.com
Fixes: d6d86c0a7f ("mm/balloon_compaction: redesign ballooned pages management")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reported-by: Vratislav Bendel <vbendel@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vratislav Bendel <vbendel@redhat.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: <stable@vger.kernel.org> [3.12 - 4.7]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently, buffer_migrate_page_norefs() was constantly failing because
buffer_migrate_lock_buffers() grabbed reference on each buffer. In
fact, there's no reason for buffer_migrate_lock_buffers() to grab any
buffer references as the page is locked during all our operation and
thus nobody can reclaim buffers from the page.
So remove grabbing of buffer references which also makes
buffer_migrate_page_norefs() succeed.
Link: http://lkml.kernel.org/r/20190116131217.7226-1-jack@suse.cz
Fixes: 89cb0888ca "mm: migrate: provide buffer_migrate_page_norefs()"
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This reverts b43a999005
The reverted commit caused issues with migration and poisoning of anon
huge pages. The LTP move_pages12 test will cause an "unable to handle
kernel NULL pointer" BUG would occur with stack similar to:
RIP: 0010:down_write+0x1b/0x40
Call Trace:
migrate_pages+0x81f/0xb90
__ia32_compat_sys_migrate_pages+0x190/0x190
do_move_pages_to_node.isra.53.part.54+0x2a/0x50
kernel_move_pages+0x566/0x7b0
__x64_sys_move_pages+0x24/0x30
do_syscall_64+0x5b/0x180
entry_SYSCALL_64_after_hwframe+0x44/0xa9
The purpose of the reverted patch was to fix some long existing races
with huge pmd sharing. It used i_mmap_rwsem for this purpose with the
idea that this could also be used to address truncate/page fault races
with another patch. Further analysis has determined that i_mmap_rwsem
can not be used to address all these hugetlbfs synchronization issues.
Therefore, revert this patch while working an another approach to the
underlying issues.
Link: http://lkml.kernel.org/r/20190103235452.29335-2-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reported-by: Jan Stancek <jstancek@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "Add support for fast mremap".
This series speeds up the mremap(2) syscall by copying page tables at
the PMD level even for non-THP systems. There is concern that the extra
'address' argument that mremap passes to pte_alloc may do something
subtle architecture related in the future that may make the scheme not
work. Also we find that there is no point in passing the 'address' to
pte_alloc since its unused. This patch therefore removes this argument
tree-wide resulting in a nice negative diff as well. Also ensuring
along the way that the enabled architectures do not do anything funky
with the 'address' argument that goes unnoticed by the optimization.
Build and boot tested on x86-64. Build tested on arm64. The config
enablement patch for arm64 will be posted in the future after more
testing.
The changes were obtained by applying the following Coccinelle script.
(thanks Julia for answering all Coccinelle questions!).
Following fix ups were done manually:
* Removal of address argument from pte_fragment_alloc
* Removal of pte_alloc_one_fast definitions from m68k and microblaze.
// Options: --include-headers --no-includes
// Note: I split the 'identifier fn' line, so if you are manually
// running it, please unsplit it so it runs for you.
virtual patch
@pte_alloc_func_def depends on patch exists@
identifier E2;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
type T2;
@@
fn(...
- , T2 E2
)
{ ... }
@pte_alloc_func_proto_noarg depends on patch exists@
type T1, T2, T3, T4;
identifier fn =~ "^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@
(
- T3 fn(T1, T2);
+ T3 fn(T1);
|
- T3 fn(T1, T2, T4);
+ T3 fn(T1, T2);
)
@pte_alloc_func_proto depends on patch exists@
identifier E1, E2, E4;
type T1, T2, T3, T4;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@
(
- T3 fn(T1 E1, T2 E2);
+ T3 fn(T1 E1);
|
- T3 fn(T1 E1, T2 E2, T4 E4);
+ T3 fn(T1 E1, T2 E2);
)
@pte_alloc_func_call depends on patch exists@
expression E2;
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
@@
fn(...
-, E2
)
@pte_alloc_macro depends on patch exists@
identifier fn =~
"^(__pte_alloc|pte_alloc_one|pte_alloc|__pte_alloc_kernel|pte_alloc_one_kernel)$";
identifier a, b, c;
expression e;
position p;
@@
(
- #define fn(a, b, c) e
+ #define fn(a, b) e
|
- #define fn(a, b) e
+ #define fn(a) e
)
Link: http://lkml.kernel.org/r/20181108181201.88826-2-joelaf@google.com
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Suggested-by: Kirill A. Shutemov <kirill@shutemov.name>
Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
While looking at BUGs associated with invalid huge page map counts, it was
discovered and observed that a huge pte pointer could become 'invalid' and
point to another task's page table. Consider the following:
A task takes a page fault on a shared hugetlbfs file and calls
huge_pte_alloc to get a ptep. Suppose the returned ptep points to a
shared pmd.
Now, another task truncates the hugetlbfs file. As part of truncation, it
unmaps everyone who has the file mapped. If the range being truncated is
covered by a shared pmd, huge_pmd_unshare will be called. For all but the
last user of the shared pmd, huge_pmd_unshare will clear the pud pointing
to the pmd. If the task in the middle of the page fault is not the last
user, the ptep returned by huge_pte_alloc now points to another task's
page table or worse. This leads to bad things such as incorrect page
map/reference counts or invalid memory references.
To fix, expand the use of i_mmap_rwsem as follows:
- i_mmap_rwsem is held in read mode whenever huge_pmd_share is called.
huge_pmd_share is only called via huge_pte_alloc, so callers of
huge_pte_alloc take i_mmap_rwsem before calling. In addition, callers
of huge_pte_alloc continue to hold the semaphore until finished with the
ptep.
- i_mmap_rwsem is held in write mode whenever huge_pmd_unshare is
called.
[mike.kravetz@oracle.com: add explicit check for mapping != null]
Link: http://lkml.kernel.org/r/20181218223557.5202-2-mike.kravetz@oracle.com
Fixes: 39dde65c99 ("shared page table for hugetlb page")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Prakash Sangappa <prakash.sangappa@oracle.com>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All callers of migrate_page_move_mapping() now pass NULL for 'head'
argument. Drop it.
Link: http://lkml.kernel.org/r/20181211172143.7358-7-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Provide a variant of buffer_migrate_page() that also checks whether there
are no unexpected references to buffer heads. This function will then be
safe to use for block device pages.
[akpm@linux-foundation.org: remove EXPORT_SYMBOL(buffer_migrate_page_norefs)]
Link: http://lkml.kernel.org/r/20181211172143.7358-5-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
buffer_migrate_page() is the only caller of migrate_page_lock_buffers()
move it close to it and also drop the now unused stub for !CONFIG_BLOCK.
Link: http://lkml.kernel.org/r/20181211172143.7358-4-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Lock buffers before calling into migrate_page_move_mapping() so that that
function doesn't have to know about buffers (which is somewhat unexpected
anyway) and all the buffer head logic is in buffer_migrate_page().
Link: http://lkml.kernel.org/r/20181211172143.7358-3-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "mm: migrate: Fix page migration stalls for blkdev pages".
This patchset deals with page migration stalls that were reported by our
customer due to a block device page that had a bufferhead that was in the
bh LRU cache.
The patchset modifies the page migration code so that bufferheads are
completely handled inside buffer_migrate_page() and then provides a new
migration helper for pages with buffer heads that is safe to use even for
block device pages and that also deals with bh lrus.
This patch (of 6):
Factor out function to compute number of expected page references in
migrate_page_move_mapping(). Note that we move hpage_nr_pages() and
page_has_private() checks from under xas_lock_irq() however this is safe
since we hold page lock.
[jack@suse.cz: fix expected_page_refs()]
Link: http://lkml.kernel.org/r/20181217131710.GB8611@quack2.suse.cz
Link: http://lkml.kernel.org/r/20181211172143.7358-2-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To avoid having to change many call sites everytime we want to add a
parameter use a structure to group all parameters for the mmu_notifier
invalidate_range_start/end cakks. No functional changes with this patch.
[akpm@linux-foundation.org: coding style fixes]
Link: http://lkml.kernel.org/r/20181205053628.3210-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Felix Kuehling <felix.kuehling@amd.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
From: Jérôme Glisse <jglisse@redhat.com>
Subject: mm/mmu_notifier: use structure for invalidate_range_start/end calls v3
fix build warning in migrate.c when CONFIG_MMU_NOTIFIER=n
Link: http://lkml.kernel.org/r/20181213171330.8489-3-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Waiting on a page migration entry has used wait_on_page_locked() all along
since 2006: but you cannot safely wait_on_page_locked() without holding a
reference to the page, and that extra reference is enough to make
migrate_page_move_mapping() fail with -EAGAIN, when a racing task faults
on the entry before migrate_page_move_mapping() gets there.
And that failure is retried nine times, amplifying the pain when trying to
migrate a popular page. With a single persistent faulter, migration
sometimes succeeds; with two or three concurrent faulters, success becomes
much less likely (and the more the page was mapped, the worse the overhead
of unmapping and remapping it on each try).
This is especially a problem for memory offlining, where the outer level
retries forever (or until terminated from userspace), because a heavy
refault workload can trigger an endless loop of migration failures.
wait_on_page_locked() is the wrong tool for the job.
David Herrmann (but was he the first?) noticed this issue in 2014:
https://marc.info/?l=linux-mm&m=140110465608116&w=2
Tim Chen started a thread in August 2017 which appears relevant:
https://marc.info/?l=linux-mm&m=150275941014915&w=2 where Kan Liang went
on to implicate __migration_entry_wait():
https://marc.info/?l=linux-mm&m=150300268411980&w=2 and the thread ended
up with the v4.14 commits: 2554db9165 ("sched/wait: Break up long wake
list walk") 11a19c7b09 ("sched/wait: Introduce wakeup boomark in
wake_up_page_bit")
Baoquan He reported "Memory hotplug softlock issue" 14 November 2018:
https://marc.info/?l=linux-mm&m=154217936431300&w=2
We have all assumed that it is essential to hold a page reference while
waiting on a page lock: partly to guarantee that there is still a struct
page when MEMORY_HOTREMOVE is configured, but also to protect against
reuse of the struct page going to someone who then holds the page locked
indefinitely, when the waiter can reasonably expect timely unlocking.
But in fact, so long as wait_on_page_bit_common() does the put_page(), and
is careful not to rely on struct page contents thereafter, there is no
need to hold a reference to the page while waiting on it. That does mean
that this case cannot go back through the loop: but that's fine for the
page migration case, and even if used more widely, is limited by the "Stop
walking if it's locked" optimization in wake_page_function().
Add interface put_and_wait_on_page_locked() to do this, using "behavior"
enum in place of "lock" arg to wait_on_page_bit_common() to implement it.
No interruptible or killable variant needed yet, but they might follow: I
have a vague notion that reporting -EINTR should take precedence over
return from wait_on_page_bit_common() without knowing the page state, so
arrange it accordingly - but that may be nothing but pedantic.
__migration_entry_wait() still has to take a brief reference to the page,
prior to calling put_and_wait_on_page_locked(): but now that it is dropped
before waiting, the chance of impeding page migration is very much
reduced. Should we perhaps disable preemption across this?
shrink_page_list()'s __ClearPageLocked(): that was a surprise! This
survived a lot of testing before that showed up. PageWaiters may have
been set by wait_on_page_bit_common(), and the reference dropped, just
before shrink_page_list() succeeds in freezing its last page reference: in
such a case, unlock_page() must be used. Follow the suggestion from
Michal Hocko, just revert a978d6f521 ("mm: unlockless reclaim") now:
that optimization predates PageWaiters, and won't buy much these days; but
we can reinstate it for the !PageWaiters case if anyone notices.
It does raise the question: should vmscan.c's is_page_cache_freeable() and
__remove_mapping() now treat a PageWaiters page as if an extra reference
were held? Perhaps, but I don't think it matters much, since
shrink_page_list() already had to win its trylock_page(), so waiters are
not very common there: I noticed no difference when trying the bigger
change, and it's surely not needed while put_and_wait_on_page_locked() is
only used for page migration.
[willy@infradead.org: add put_and_wait_on_page_locked() kerneldoc]
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261121330.1116@eggly.anvils
Signed-off-by: Hugh Dickins <hughd@google.com>
Reported-by: Baoquan He <bhe@redhat.com>
Tested-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Nick Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull XArray conversion from Matthew Wilcox:
"The XArray provides an improved interface to the radix tree data
structure, providing locking as part of the API, specifying GFP flags
at allocation time, eliminating preloading, less re-walking the tree,
more efficient iterations and not exposing RCU-protected pointers to
its users.
This patch set
1. Introduces the XArray implementation
2. Converts the pagecache to use it
3. Converts memremap to use it
The page cache is the most complex and important user of the radix
tree, so converting it was most important. Converting the memremap
code removes the only other user of the multiorder code, which allows
us to remove the radix tree code that supported it.
I have 40+ followup patches to convert many other users of the radix
tree over to the XArray, but I'd like to get this part in first. The
other conversions haven't been in linux-next and aren't suitable for
applying yet, but you can see them in the xarray-conv branch if you're
interested"
* 'xarray' of git://git.infradead.org/users/willy/linux-dax: (90 commits)
radix tree: Remove multiorder support
radix tree test: Convert multiorder tests to XArray
radix tree tests: Convert item_delete_rcu to XArray
radix tree tests: Convert item_kill_tree to XArray
radix tree tests: Move item_insert_order
radix tree test suite: Remove multiorder benchmarking
radix tree test suite: Remove __item_insert
memremap: Convert to XArray
xarray: Add range store functionality
xarray: Move multiorder_check to in-kernel tests
xarray: Move multiorder_shrink to kernel tests
xarray: Move multiorder account test in-kernel
radix tree test suite: Convert iteration test to XArray
radix tree test suite: Convert tag_tagged_items to XArray
radix tree: Remove radix_tree_clear_tags
radix tree: Remove radix_tree_maybe_preload_order
radix tree: Remove split/join code
radix tree: Remove radix_tree_update_node_t
page cache: Finish XArray conversion
dax: Convert page fault handlers to XArray
...
Linus Torvalds