FOLL_FORCE is really only for ptrace access. As we unpin the pinned pages
using unpin_user_pages_dirty_lock(true), the assumption is that all these
pages are writable.
FOLL_FORCE in this case seems to be a legacy leftover. Let's just remove
it.
Link: https://lkml.kernel.org/r/20221116102659.70287-18-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: David Airlie <airlied@gmail.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
FOLL_FORCE is really only for ptrace access. According to commit
707947247e ("media: videobuf2-vmalloc: get_userptr: buffers are always
writable"), get_vaddr_frames() currently pins all pages writable as a
workaround for issues with read-only buffers.
FOLL_FORCE, however, seems to be a legacy leftover as it predates
commit 707947247e ("media: videobuf2-vmalloc: get_userptr: buffers are
always writable"). Let's just remove it.
Once the read-only buffer issue has been resolved, FOLL_WRITE could
again be set depending on the DMA direction.
Link: https://lkml.kernel.org/r/20221116102659.70287-17-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
FOLL_FORCE is really only for ptrace access. R/O pinning a page is
supposed to fail if the VMA misses proper access permissions (no VM_READ).
Let's just remove FOLL_FORCE usage here; there would have to be a pretty
good reason to allow arbitrary drivers to R/O pin pages in a PROT_NONE
VMA. Most probably, FOLL_FORCE usage is just some legacy leftover.
Link: https://lkml.kernel.org/r/20221116102659.70287-16-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Andy Walls <awalls@md.metrocast.net>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
GUP now supports reliable R/O long-term pinning in COW mappings, such
that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
far in one corner case (DAXFS file with holes), which can be ignored
because GUP does not support long-term pinning in fsdax (see
check_vma_flags()).
commit cd5297b085 ("drm/etnaviv: Use FOLL_FORCE for userptr")
documents that FOLL_FORCE | FOLL_WRITE was really only used for reliable
R/O pinning.
Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
using FOLL_FORCE, which is really only for ptrace access.
Link: https://lkml.kernel.org/r/20221116102659.70287-15-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Russell King <linux+etnaviv@armlinux.org.uk>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: David Airlie <airlied@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
GUP now supports reliable R/O long-term pinning in COW mappings, such
that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
far in one corner case (DAXFS file with holes), which can be ignored
because GUP does not support long-term pinning in fsdax (see
check_vma_flags()).
Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
using FOLL_FORCE, which is really only for ptrace access.
Link: https://lkml.kernel.org/r/20221116102659.70287-14-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
GUP now supports reliable R/O long-term pinning in COW mappings, such
that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
far in one corner case (DAXFS file with holes), which can be ignored
because GUP does not support long-term pinning in fsdax (see
check_vma_flags()).
Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
using FOLL_FORCE, which is really only for ptrace access.
Link: https://lkml.kernel.org/r/20221116102659.70287-13-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Bernard Metzler <bmt@zurich.ibm.com>
Cc: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
GUP now supports reliable R/O long-term pinning in COW mappings, such
that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
far in one corner case (DAXFS file with holes), which can be ignored
because GUP does not support long-term pinning in fsdax (see
check_vma_flags()).
Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
using FOLL_FORCE, which is really only for ptrace access.
Link: https://lkml.kernel.org/r/20221116102659.70287-12-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Christian Benvenuti <benve@cisco.com>
Cc: Nelson Escobar <neescoba@cisco.com>
Cc: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
GUP now supports reliable R/O long-term pinning in COW mappings, such
that we break COW early. MAP_SHARED VMAs only use the shared zeropage so
far in one corner case (DAXFS file with holes), which can be ignored
because GUP does not support long-term pinning in fsdax (see
check_vma_flags()).
Consequently, FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM is no longer required
for reliable R/O long-term pinning: FOLL_LONGTERM is sufficient. So stop
using FOLL_FORCE, which is really only for ptrace access.
Link: https://lkml.kernel.org/r/20221116102659.70287-11-david@redhat.com
Tested-by: Leon Romanovsky <leonro@nvidia.com> [over mlx4 and mlx5]
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We already support reliable R/O pinning of anonymous memory. However,
assume we end up pinning (R/O long-term) a pagecache page or the shared
zeropage inside a writable private ("COW") mapping. The next write access
will trigger a write-fault and replace the pinned page by an exclusive
anonymous page in the process page tables to break COW: the pinned page no
longer corresponds to the page mapped into the process' page table.
Now that FAULT_FLAG_UNSHARE can break COW on anything mapped into a
COW mapping, let's properly break COW first before R/O long-term
pinning something that's not an exclusive anon page inside a COW
mapping. FAULT_FLAG_UNSHARE will break COW and map an exclusive anon page
instead that can get pinned safely.
With this change, we can stop using FOLL_FORCE|FOLL_WRITE for reliable
R/O long-term pinning in COW mappings.
With this change, the new R/O long-term pinning tests for non-anonymous
memory succeed:
# [RUN] R/O longterm GUP pin ... with shared zeropage
ok 151 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with memfd
ok 152 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with tmpfile
ok 153 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with huge zeropage
ok 154 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with memfd hugetlb (2048 kB)
ok 155 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with memfd hugetlb (1048576 kB)
ok 156 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with shared zeropage
ok 157 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with memfd
ok 158 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with tmpfile
ok 159 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with huge zeropage
ok 160 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (2048 kB)
ok 161 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (1048576 kB)
ok 162 Longterm R/O pin is reliable
Note 1: We don't care about short-term R/O-pinning, because they have
snapshot semantics: they are not supposed to observe modifications that
happen after pinning.
As one example, assume we start direct I/O to read from a page and store
page content into a file: modifications to page content after starting
direct I/O are not guaranteed to end up in the file. So even if we'd pin
the shared zeropage, the end result would be as expected -- getting zeroes
stored to the file.
Note 2: For shared mappings we'll now always fallback to the slow path to
lookup the VMA when R/O long-term pining. While that's the necessary price
we have to pay right now, it's actually not that bad in practice: most
FOLL_LONGTERM users already specify FOLL_WRITE, for example, along with
FOLL_FORCE because they tried dealing with COW mappings correctly ...
Note 3: For users that use FOLL_LONGTERM right now without FOLL_WRITE,
such as VFIO, we'd now no longer pin the shared zeropage. Instead, we'd
populate exclusive anon pages that we can pin. There was a concern that
this could affect the memlock limit of existing setups.
For example, a VM running with VFIO could run into the memlock limit and
fail to run. However, we essentially had the same behavior already in
commit 17839856fd ("gup: document and work around "COW can break either
way" issue") which got merged into some enterprise distros, and there were
not any such complaints. So most probably, we're fine.
Link: https://lkml.kernel.org/r/20221116102659.70287-10-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Extend FAULT_FLAG_UNSHARE to break COW on anything mapped into a
COW (i.e., private writable) mapping and adjust the documentation
accordingly.
FAULT_FLAG_UNSHARE will now also break COW when encountering the shared
zeropage, a pagecache page, a PFNMAP, ... inside a COW mapping, by
properly replacing the mapped page/pfn by a private copy (an exclusive
anonymous page).
Note that only do_wp_page() needs care: hugetlb_wp() already handles
FAULT_FLAG_UNSHARE correctly. wp_huge_pmd()/wp_huge_pud() also handles it
correctly, for example, splitting the huge zeropage on FAULT_FLAG_UNSHARE
such that we can handle FAULT_FLAG_UNSHARE on the PTE level.
This change is a requirement for reliable long-term R/O pinning in
COW mappings.
Link: https://lkml.kernel.org/r/20221116102659.70287-9-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
If we already have a PMD/PUD mapped write-protected in a private mapping
and we want to break COW either due to FAULT_FLAG_WRITE or
FAULT_FLAG_UNSHARE, there is no need to inform the file system just like on
the PTE path.
Let's just split (->zap) + fallback in that case.
This is a preparation for more generic FAULT_FLAG_UNSHARE support in
COW mappings.
Link: https://lkml.kernel.org/r/20221116102659.70287-8-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We want to extent FAULT_FLAG_UNSHARE support to anything mapped into a
COW mapping (pagecache page, zeropage, PFN, ...), not just anonymous pages.
Let's prepare for that by handling shared mappings first such that we can
handle private mappings last.
While at it, use folio-based functions instead of page-based functions
where we touch the code either way.
Link: https://lkml.kernel.org/r/20221116102659.70287-7-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's catch abuse of FAULT_FLAG_WRITE early, such that we don't have to
care in all other handlers and might get "surprises" if we forget to do
so.
Write faults without VM_MAYWRITE don't make any sense, and our
maybe_mkwrite() logic could have hidden such abuse for now.
Write faults without VM_WRITE on something that is not a COW mapping is
similarly broken, and e.g., do_wp_page() could end up placing an
anonymous page into a shared mapping, which would be bad.
This is a preparation for reliable R/O long-term pinning of pages in
private mappings, whereby we want to make sure that we will never break
COW in a read-only private mapping.
Link: https://lkml.kernel.org/r/20221116102659.70287-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
For now, FAULT_FLAG_UNSHARE only applies to anonymous pages, which
implies a COW mapping. Let's hide FAULT_FLAG_UNSHARE early if we're not
dealing with a COW mapping, such that we treat it like a read fault as
documented and don't have to worry about the flag throughout all fault
handlers.
While at it, centralize the check for mutual exclusion of
FAULT_FLAG_UNSHARE and FAULT_FLAG_WRITE and just drop the check that
either flag is set in the WP handler.
Link: https://lkml.kernel.org/r/20221116102659.70287-5-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's test whether R/O long-term pinning is reliable for non-anonymous
memory: when R/O long-term pinning a page, the expectation is that we
break COW early before pinning, such that actual write access via the
page tables won't break COW later and end up replacing the R/O-pinned
page in the page table.
Consequently, R/O long-term pinning in private mappings would only target
exclusive anonymous pages.
For now, all tests fail:
# [RUN] R/O longterm GUP pin ... with shared zeropage
not ok 151 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with memfd
not ok 152 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with tmpfile
not ok 153 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with huge zeropage
not ok 154 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with memfd hugetlb (2048 kB)
not ok 155 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP pin ... with memfd hugetlb (1048576 kB)
not ok 156 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with shared zeropage
not ok 157 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with memfd
not ok 158 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with tmpfile
not ok 159 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with huge zeropage
not ok 160 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (2048 kB)
not ok 161 Longterm R/O pin is reliable
# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (1048576 kB)
not ok 162 Longterm R/O pin is reliable
Link: https://lkml.kernel.org/r/20221116102659.70287-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's add basic tests for COW with non-anonymous pages in private
mappings: write access should properly trigger COW and result in the
private changes not being visible through other page mappings.
Especially, add tests for:
* Zeropage
* Huge zeropage
* Ordinary pagecache pages via memfd and tmpfile()
* Hugetlb pages via memfd
Fortunately, all tests pass.
Link: https://lkml.kernel.org/r/20221116102659.70287-3-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/gup: remove FOLL_FORCE usage from drivers (reliable R/O
long-term pinning)".
For now, we did not support reliable R/O long-term pinning in COW
mappings. That means, if we would trigger R/O long-term pinning in
MAP_PRIVATE mapping, we could end up pinning the (R/O-mapped) shared
zeropage or a pagecache page.
The next write access would trigger a write fault and replace the pinned
page by an exclusive anonymous page in the process page table; whatever
the process would write to that private page copy would not be visible by
the owner of the previous page pin: for example, RDMA could read stale
data. The end result is essentially an unexpected and hard-to-debug
memory corruption.
Some drivers tried working around that limitation by using
"FOLL_FORCE|FOLL_WRITE|FOLL_LONGTERM" for R/O long-term pinning for now.
FOLL_WRITE would trigger a write fault, if required, and break COW before
pinning the page. FOLL_FORCE is required because the VMA might lack write
permissions, and drivers wanted to make that working as well, just like
one would expect (no write access, but still triggering a write access to
break COW).
However, that is not a practical solution, because
(1) Drivers that don't stick to that undocumented and debatable pattern
would still run into that issue. For example, VFIO only uses
FOLL_LONGTERM for R/O long-term pinning.
(2) Using FOLL_WRITE just to work around a COW mapping + page pinning
limitation is unintuitive. FOLL_WRITE would, for example, mark the
page softdirty or trigger uffd-wp, even though, there actually isn't
going to be any write access.
(3) The purpose of FOLL_FORCE is debug access, not access without lack of
VMA permissions by arbitrarty drivers.
So instead, make R/O long-term pinning work as expected, by breaking COW
in a COW mapping early, such that we can remove any FOLL_FORCE usage from
drivers and make FOLL_FORCE ptrace-specific (renaming it to FOLL_PTRACE).
More details in patch #8.
This patch (of 19):
Originally, the plan was to have a separate tests for testing COW of
non-anonymous (e.g., shared zeropage) pages.
Turns out, that we'd need a lot of similar functionality and that there
isn't a really good reason to separate it. So let's prepare for non-anon
tests by renaming to "cow".
Link: https://lkml.kernel.org/r/20221116102659.70287-1-david@redhat.com
Link: https://lkml.kernel.org/r/20221116102659.70287-2-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Walls <awalls@md.metrocast.net>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bernard Metzler <bmt@zurich.ibm.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Benvenuti <benve@cisco.com>
Cc: Christian Gmeiner <christian.gmeiner@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hans Verkuil <hverkuil@xs4all.nl>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Inki Dae <inki.dae@samsung.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kentaro Takeda <takedakn@nttdata.co.jp>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Leon Romanovsky <leonro@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nelson Escobar <neescoba@cisco.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oded Gabbay <ogabbay@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <linux+etnaviv@armlinux.org.uk>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tomasz Figa <tfiga@chromium.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Commit 6a108a14fa ("kconfig: rename CONFIG_EMBEDDED to CONFIG_EXPERT")
introduces CONFIG_EXPERT to carry the previous intent of CONFIG_EMBEDDED
and just gives that intent a much better name. That has been clearly a
good and long overdue renaming, and it is clearly an improvement to the
kernel build configuration that has shown to help managing the kernel
build configuration in the last decade.
However, rather than bravely and radically just deleting CONFIG_EMBEDDED,
this commit gives CONFIG_EMBEDDED a new intended semantics, but keeps it
open for future contributors to implement that intended semantics:
A new CONFIG_EMBEDDED option is added that automatically selects
CONFIG_EXPERT when enabled and can be used in the future to isolate
options that should only be considered for embedded systems (RISC
architectures, SLOB, etc).
Since then, this CONFIG_EMBEDDED implicitly had two purposes:
- It can make even more options visible beyond what CONFIG_EXPERT makes
visible. In other words, it may introduce another level of enabling the
visibility of configuration options: always visible, visible with
CONFIG_EXPERT and visible with CONFIG_EMBEDDED.
- Set certain default values of some configurations differently,
following the assumption that configuring a kernel build for an
embedded system generally starts with a different set of default values
compared to kernel builds for all other kind of systems.
Considering the second purpose, note that already probably arguing that a
kernel build for an embedded system would choose some values differently
is already tricky: the set of embedded systems with Linux kernels is
already quite diverse. Many embedded system have powerful CPUs and it
would not be clear that all embedded systems just optimize towards one
specific aspect, e.g., a smaller kernel image size. So, it is unclear if
starting with "one set of default configuration" that is induced by
CONFIG_EMBEDDED is a good offer for developers configuring their kernels.
Also, the differences of needed user-space features in an embedded system
compared to a non-embedded system are probably difficult or even
impossible to name in some generic way.
So it is not surprising that in the last decade hardly anyone has
contributed changes to make something default differently in case of
CONFIG_EMBEDDED=y.
Currently, in v6.0-rc4, SECRETMEM is the only config switched off if
CONFIG_EMBEDDED=y.
As long as that is actually the only option that currently is selected or
deselected, it is better to just make SECRETMEM configurable at build time
by experts using menuconfig instead.
Make SECRETMEM configurable when EXPERT is set and otherwise default to
yes. Further, SECRETMEM needs ARCH_HAS_SET_DIRECT_MAP.
This allows us to remove CONFIG_EMBEDDED in the close future.
Link: https://lkml.kernel.org/r/20221116131922.25533-1-lukas.bulwahn@gmail.com
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This restriction was created because FOLL_LONGTERM used to scan the vma
list, so it could not tolerate becoming unlocked. That was fixed in
commit 52650c8b46 ("mm/gup: remove the vma allocation from
gup_longterm_locked()") and the restriction on !vma was removed.
However, the locked restriction remained, even though it isn't necessary
anymore.
Adjust __gup_longterm_locked() so it can handle the mmap_read_lock()
becoming unlocked while it is looping for migration. Migration does not
require the mmap_read_sem because it is only handling struct pages. If we
had to unlock then ensure the whole thing returns unlocked.
Remove __get_user_pages_remote() and __gup_longterm_unlocked(). These
cases can now just directly call other functions.
Link: https://lkml.kernel.org/r/0-v1-b9ae39aa8884+14dbb-gup_longterm_locked_jgg@nvidia.com
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When testing overflow and overread, there is no need to keep unnecessary
compilation warnings, we should simply ignore them.
The motivation for this patch is to eliminate the compilation warning,
maybe one day we will compile the kernel with "-Werror -Wall", at which
point this compilation warning will turn into a compilation error, we
should fix this error in advance.
How to reproduce the problem (with gcc-11.3.1):
$ make -C tools/testing/selftests/
...
warning: `write' reading 4294967295 bytes from a region of size 1
[-Wstringop-overread]
warning: `read' writing 4294967295 bytes into a region of size 25
overflows the destination [-Wstringop-overflow=]
"-Wno-stringop-overread" is supported at least in gcc-11.1.0.
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=d14c547abd484d3540b692bb8048c4a6efe92c8b
Link: https://lkml.kernel.org/r/tencent_51C4ACA8CB3895C2D7F35178440283602107@qq.com
Signed-off-by: Rong Tao <rongtao@cestc.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The ei pointer does not need to cast the type.
Link: https://lkml.kernel.org/r/20221107015659.3221-1-zeming@nfschina.com
Signed-off-by: Li zeming <zeming@nfschina.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently, drop_caches are reclaiming node-by-node, looping on each node
until reclaim could not make progress. This can however leave quite some
slab entries (such as filesystem inodes) unreclaimed if objects say on
node 1 keep objects on node 0 pinned. So move the "loop until no
progress" loop to the node-by-node iteration to retry reclaim also on
other nodes if reclaim on some nodes made progress. This fixes problem
when drop_caches was not reclaiming lots of otherwise perfectly fine to
reclaim inodes.
Link: https://lkml.kernel.org/r/20221115123255.12559-1-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: You Zhou <you.zhou@intel.com>
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Since commit 9a10064f56 ("mm: add a field to store names for private
anonymous memory"), name for private anonymous memory, but not shared
anonymous, can be set. However, naming shared anonymous memory just as
useful for tracking purposes.
Extend the functionality to be able to set names for shared anon.
There are two ways to create anonymous shared memory, using memfd or
directly via mmap():
1. fd = memfd_create(...)
mem = mmap(..., MAP_SHARED, fd, ...)
2. mem = mmap(..., MAP_SHARED | MAP_ANONYMOUS, -1, ...)
In both cases the anonymous shared memory is created the same way by
mapping an unlinked file on tmpfs.
The memfd way allows to give a name for anonymous shared memory, but
not useful when parts of shared memory require to have distinct names.
Example use case: The VMM maps VM memory as anonymous shared memory (not
private because VMM is sandboxed and drivers are running in their own
processes). However, the VM tells back to the VMM how parts of the memory
are actually used by the guest, how each of the segments should be backed
(i.e. 4K pages, 2M pages), and some other information about the segments.
The naming allows us to monitor the effective memory footprint for each
of these segments from the host without looking inside the guest.
Sample output:
/* Create shared anonymous segmenet */
anon_shmem = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
MAP_SHARED | MAP_ANONYMOUS, -1, 0);
/* Name the segment: "MY-NAME" */
rv = prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME,
anon_shmem, SIZE, "MY-NAME");
cat /proc/<pid>/maps (and smaps):
7fc8e2b4c000-7fc8f2b4c000 rw-s 00000000 00:01 1024 [anon_shmem:MY-NAME]
If the segment is not named, the output is:
7fc8e2b4c000-7fc8f2b4c000 rw-s 00000000 00:01 1024 /dev/zero (deleted)
Link: https://lkml.kernel.org/r/20221115020602.804224-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Colin Cross <ccross@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: xu xin <cgel.zte@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The shrinker.h header depends on a user including other headers before it
for types used by shrinker.h. Fix this by including the appropriate
headers in shrinker.h.
./include/linux/shrinker.h:13:9: error: unknown type name `gfp_t'
13 | gfp_t gfp_mask;
| ^~~~~
./include/linux/shrinker.h:71:26: error: field `list' has incomplete type
71 | struct list_head list;
| ^~~~
./include/linux/shrinker.h:82:9: error: unknown type name `atomic_long_t'
82 | atomic_long_t *nr_deferred;
|
Link: https://lkml.kernel.org/r/20221114235949.201749-1-tjmercier@google.com
Fixes: 83aeeada7c ("vmscan: use atomic-long for shrinker batching")
Fixes: b0d40c92ad ("superblock: introduce per-sb cache shrinker infrastructure")
Signed-off-by: T.J. Mercier <tjmercier@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The common hugetlb unmap routine __unmap_hugepage_range performs mmu
notification calls. However, in the case where __unmap_hugepage_range is
called via __unmap_hugepage_range_final, mmu notification calls are
performed earlier in other calling routines.
Remove mmu notification calls from __unmap_hugepage_range. Add
notification calls to the only other caller: unmap_hugepage_range.
unmap_hugepage_range is called for truncation and hole punch, so change
notification type from UNMAP to CLEAR as this is more appropriate.
Link: https://lkml.kernel.org/r/20221114235507.294320-4-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: Peter Xu <peterx@redhat.com>
Cc: Wei Chen <harperchen1110@gmail.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Let's add one sanity check for CONFIG_DEBUG_VM on the write bit in
whatever chance we have when walking through the pgtables. It can bring
the error earlier even before the app notices the data was corrupted on
the snapshot. Also it helps us to identify this is a wrong pgtable setup,
so hopefully a great information to have for debugging too.
Link: https://lkml.kernel.org/r/20221114000447.1681003-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
MADV_FREE pages have been moved into the LRU_INACTIVE_FILE list by commit
f7ad2a6cb9 ("mm: move MADV_FREE pages into LRU_INACTIVE_FILE list").
Link: https://lkml.kernel.org/r/20221111034639.3593380-1-wenjian1@xiaomi.com
Signed-off-by: Jian Wen <wenjian1@xiaomi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
alloc_memory_type() returns error pointers on error instead of NULL. Use
IS_ERR() to check the return value to fix this.
Link: https://lkml.kernel.org/r/20221110030751.1627266-1-linmq006@gmail.com
Fixes: 7b88bda376 ("mm/demotion/dax/kmem: set node's abstract distance to MEMTIER_DEFAULT_DAX_ADISTANCE")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Wei Xu <weixugc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Quite straightforward, the page functions are converted to corresponding
folio functions. Same for comments.
THP specific code are converted to be large folio.
Link: https://lkml.kernel.org/r/20221109012348.93849-3-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "migrate: convert migrate_pages()/unmap_and_move() to use
folios", v2.
The conversion is quite straightforward, just replace the page API to the
corresponding folio API. migrate_pages() and unmap_and_move() mostly work
with folios (head pages) only.
This patch (of 2):
Quite straightforward, the page functions are converted to corresponding
folio functions. Same for comments.
Link: https://lkml.kernel.org/r/20221109012348.93849-1-ying.huang@intel.com
Link: https://lkml.kernel.org/r/20221109012348.93849-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Revert commit 8315682148 ("mm: migration: fix the FOLL_GET failure on
following huge page"), since after commit 1a6baaa0db ("s390/hugetlb:
switch to generic version of follow_huge_pud()") and commit 57a196a584
("hugetlb: simplify hugetlb handling in follow_page_mask") were merged,
now all the following huge page routines can support FOLL_GET operation.
Link: https://lkml.kernel.org/r/496786039852aba90ffa68f10d0df3f4236a990b.1667983080.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Haiyue Wang <haiyue.wang@intel.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
commit fdf756f712 ("sched: Fix more TASK_state comparisons") makes
hung_task not to monitor TASK_IDLE tasks. The special handling to
workaround hung_task warnings is not required anymore.
Link: https://lkml.kernel.org/r/1667986006-25420-1-git-send-email-quic_pkondeti@quicinc.com
Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a new flag to zram block state that shows if the page is
incompressible: that none of the algorithm (including secondary ones)
could compress it.
Link: https://lkml.kernel.org/r/20221109115047.2921851-14-senozhatsky@chromium.org
Suggested-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Recompression iterates through all the registered secondary compression
algorithms in order of their priorities so that we have higher chances of
finding the algorithm that compresses a particular page. This, however,
may not always be best approach and sometimes we may want to limit
recompression to only one particular algorithm. For instance, when a
higher priority algorithm uses too much power and device has a relatively
low battery level we may want to limit recompression to use only a lower
priority algorithm, which uses less power.
Introduce algo= parameter support to recompression sysfs knob so that
user-sapce can request recompression with particular algorithm only:
echo "type=idle algo=zstd" > /sys/block/zramX/recompress
Link: https://lkml.kernel.org/r/20221109115047.2921851-11-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
It makes no sense for us to recompress the object if it will be in the
same size class. We anyway don't get any memory gain. But, at the same
time, we get a CPU time overhead when inserting this object into zspage
and decompressing it afterwards.
[senozhatsky: rebased and fixed conflicts]
Link: https://lkml.kernel.org/r/20221109115047.2921851-9-senozhatsky@chromium.org
Signed-off-by: Alexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a new flag to zram block state that shows if the page was recompressed
(using alternative compression algorithm).
Link: https://lkml.kernel.org/r/20221109115047.2921851-6-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Allow zram to recompress (using secondary compression streams)
pages.
Re-compression algorithms (we support up to 3 at this stage)
are selected via recomp_algorithm:
echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm
Please read documentation for more details.
We support several recompression modes:
1) IDLE pages recompression is activated by `idle` mode
echo "type=idle" > /sys/block/zram0/recompress
2) Since there may be many idle pages user-space may pass a size
threshold value (in bytes) and we will recompress pages only
of equal or greater size:
echo "threshold=888" > /sys/block/zram0/recompress
3) HUGE pages recompression is activated by `huge` mode
echo "type=huge" > /sys/block/zram0/recompress
4) HUGE_IDLE pages recompression is activated by `huge_idle` mode
echo "type=huge_idle" > /sys/block/zram0/recompress
[senozhatsky@chromium.org: we should always zero out err variable in recompress loop[
Link: https://lkml.kernel.org/r/20221110143423.3250790-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20221109115047.2921851-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Introduce recomp_algorithm sysfs knob that controls secondary algorithm
selection used for recompression.
We will support up to 3 secondary compression algorithms which are sorted
in order of their priority. To select an algorithm user has to provide
its name and priority:
echo "algo=zstd priority=1" > /sys/block/zramX/recomp_algorithm
echo "algo=deflate priority=2" > /sys/block/zramX/recomp_algorithm
During recompression zram iterates through the list of registered
secondary algorithms in order of their priorities.
We also have a short version for cases when there is only
one secondary compression algorithm:
echo "algo=zstd" > /sys/block/zramX/recomp_algorithm
This will register zstd as the secondary algorithm with priority 1.
Link: https://lkml.kernel.org/r/20221109115047.2921851-3-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "zram: Support multiple compression streams", v5.
This series adds support for multiple compression streams. The main idea
is that different compression algorithms have different characteristics
and zram may benefit when it uses a combination of algorithms: a default
algorithm that is faster but have lower compression rate and a secondary
algorithm that can use higher compression rate at a price of slower
compression/decompression.
There are several use-case for this functionality:
- huge pages re-compression: zstd or deflate can successfully compress
huge pages (~50% of huge pages on my synthetic ChromeOS tests), IOW
pages that lzo was not able to compress.
- idle pages re-compression: idle/cold pages sit in the memory and we
may reduce zsmalloc memory usage if we recompress those idle pages.
Userspace has a number of ways to control the behavior and impact of zram
recompression: what type of pages should be recompressed, size watermarks,
etc. Please refer to documentation patch.
This patch (of 13):
The patch turns compression streams and compressor algorithm name struct
zram members into arrays, so that we can have multiple compression streams
support (in the next patches).
The patch uses a rather explicit API for compressor selection:
- Get primary (default) compression stream
zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP])
- Get secondary compression stream
zcomp_stream_get(zram->comps[ZRAM_SECONDARY_COMP])
We use similar API for compression streams put().
At this point we always have just one compression stream,
since CONFIG_ZRAM_MULTI_COMP is not yet defined.
Link: https://lkml.kernel.org/r/20221109115047.2921851-1-senozhatsky@chromium.org
Link: https://lkml.kernel.org/r/20221109115047.2921851-2-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Alexey Romanov <avromanov@sberdevices.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Flag delayed_rmap of 'struct mmu_gather' is rather a private member, but
it is still accessed directly. Instead, let the TLB gather code access
the flag.
Link: https://lkml.kernel.org/r/Y3SWCu6NRaMQ5dbD@li-4a3a4a4c-28e5-11b2-a85c-a8d192c6f089.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When we remove a page table entry, we are very careful to only free the
page after we have flushed the TLB, because other CPUs could still be
using the page through stale TLB entries until after the flush.
However, we have removed the rmap entry for that page early, which means
that functions like folio_mkclean() would end up not serializing with the
page table lock because the page had already been made invisible to rmap.
And that is a problem, because while the TLB entry exists, we could end up
with the following situation:
(a) one CPU could come in and clean it, never seeing our mapping of the
page
(b) another CPU could continue to use the stale and dirty TLB entry and
continue to write to said page
resulting in a page that has been dirtied, but then marked clean again,
all while another CPU might have dirtied it some more.
End result: possibly lost dirty data.
This extends our current TLB gather infrastructure to optionally track a
"should I do a delayed page_remove_rmap() for this page after flushing the
TLB". It uses the newly introduced 'encoded page pointer' to do that
without having to keep separate data around.
Note, this is complicated by a couple of issues:
- we want to delay the rmap removal, but not past the page table lock,
because that simplifies the memcg accounting
- only SMP configurations want to delay TLB flushing, since on UP
there are obviously no remote TLBs to worry about, and the page
table lock means there are no preemption issues either
- s390 has its own mmu_gather model that doesn't delay TLB flushing,
and as a result also does not want the delayed rmap. As such, we can
treat S390 like the UP case and use a common fallback for the "no
delays" case.
- we can track an enormous number of pages in our mmu_gather structure,
with MAX_GATHER_BATCH_COUNT batches of MAX_TABLE_BATCH pages each,
all set up to be approximately 10k pending pages.
We do not want to have a huge number of batched pages that we then
need to check for delayed rmap handling inside the page table lock.
Particularly that last point results in a noteworthy detail, where the
normal page batch gathering is limited once we have delayed rmaps pending,
in such a way that only the last batch (the so-called "active batch") in
the mmu_gather structure can have any delayed entries.
NOTE! While the "possibly lost dirty data" sounds catastrophic, for this
all to happen you need to have a user thread doing either madvise() with
MADV_DONTNEED or a full re-mmap() of the area concurrently with another
thread continuing to use said mapping.
So arguably this is about user space doing crazy things, but from a VM
consistency standpoint it's better if we track the dirty bit properly even
when user space goes off the rails.
[akpm@linux-foundation.org: fix UP build, per Linus]
Link: https://lore.kernel.org/all/B88D3073-440A-41C7-95F4-895D3F657EF2@gmail.com/
Link: https://lkml.kernel.org/r/20221109203051.1835763-4-torvalds@linux-foundation.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Reported-by: Nadav Amit <nadav.amit@gmail.com>
Tested-by: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This is purely a preparatory patch that makes all the data structures
ready for encoding flags with the mmu_gather page pointers.
The code currently always sets the flag to zero and doesn't use it yet,
but now it's tracking the type state along. The next step will be to
actually start using it.
Link: https://lkml.kernel.org/r/20221109203051.1835763-3-torvalds@linux-foundation.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
David Hildenbrand