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3a75ccba047b11a4e8c437e8347b2d1746f1d808
23847 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Lorenzo Stoakes
|
3a75ccba04 |
mm: simplify vma merge structure and expand comments
Patch series "mm: further simplify VMA merge operation", v3.
While significant efforts have been made to improve the VMA merge
operation, there remains remnants of the bad (or rather confusing) old
days, which make the code difficult to understand, more bug prone and thus
harder to modify.
This series attempts to significantly improve matters in a number of
respects - with a focus on simplifying the commit_merge() function which
actually actions the merge operation - and importantly, adjusting the two
most confusing merge cases - those in which we 'adjust' the VMA
immediately adjacent to the one being merged.
One source of confusion are the VMAs being threaded through the operation
themselves - vmg->prev, vmg->vma and vmg->next.
At the start of the operation, vmg->vma is either NULL if a new VMA is
propose to be added, or if not then a pointer to an existing VMA being
modified, and prev/next are (perhaps not present) VMAs sat immediately
before and after the range specified in vmg->start, end, respectively.
However, during the VMA merge operation, we change vmg->start, end and
pgoff to span the newly merged range and vmg->vma to either be:
a. The ultimately returned VMA (in most cases) or b. A VMA which we will
manipulate, but ultimately instead return vmg->next.
Case b. especially here is confusing for somebody reading this code, but
the fact we update this state, along with vmg->start, end, pgoff only
makes matters worse.
We simplify things by replacing vmg->vma with vmg->middle and never
changing it - this is always either NULL (for a new VMA) or the VMA being
modified between vmg->prev and vmg->next.
We further simplify by placing the merged VMA in a new vmg->target field -
whether case b. above is the case or not. The reader of the code can now
simply rely on vmg->middle being the middle VMA and vmg->target being the
ultimately merged VMA.
We additionally tackle the confusing cases where we 'adjust' VMAs other
than the one we ultimately return as the merged VMA (this includes case b.
above). These are:
(1)
merge
<----------->
|------||--------| |------------|---|
| prev || middle | -> | target | m |
|------||--------| |------------|---|
In which case middle must be adjusted so middle->vm_start is increased as
well as performing the merge.
(2) (equivalent to case b. above)
<------------->
|---------||------| |---|-------------|
| middle || next | -> | m | target |
|---------||------| |---|-------------|
In which case next must be adjusted so next->vm_start is decreased as well
as performing the merge.
This cases have previously been performed by calculating and passing
around a dubious and confusing 'adj_start' parameter along side a pointer
to an 'adjust' VMA indicating which VMA requires additional adjustment
(middle in case 1 and next in case 2).
With the VMG structure in place we are able to avoid this by simply
setting a merge flag to describe each case:
(1) Sets the vmg->__adjust_middle_start flag
(2) Sets the vmg->__adjust_next_start flag
By doing so it turns out we can vastly simplify the logic and calculate
what is required to perform the operation.
Taken together the refactorings make it far easier to understand what is
being done even in these more confusing cases, make the code far more
maintainable, debuggable, and testable, providing more internal state
indicating what is happening in the merge operation.
The changes have no functional net impact on the merge operation and
everything should still behave as it did before.
This patch (of 5):
The merge code, while much improved, still has a number of points of
confusion. As part of a broader series cleaning this up to make this more
maintainable, we start by addressing some confusion around
vma_merge_struct fields.
So far, the caller either provides no vmg->vma (a new VMA) or supplies the
existing VMA which is being altered, setting vmg->start,end,pgoff to the
proposed VMA dimensions.
vmg->vma is then updated, as are vmg->start,end,pgoff as the merge process
proceeds and the appropriate merge strategy is determined.
This is rather confusing, as vmg->vma starts off as the 'middle' VMA
between vmg->prev,next, but becomes the 'target' VMA, except in one
specific edge case (merge next, shrink middle).
Int his patch we introduce vmg->middle to describe the VMA that is between
vmg->prev and vmg->next, and does NOT change during the merge operation.
We replace vmg->vma with vmg->target, and use this only during the merge
operation itself.
Aside from the merge right, shrink middle case, this becomes the VMA that
forms the basis of the VMA that is returned. This edge case can be
addressed in a future commit.
We also add a number of comments to explain what is going on.
Finally, we adjust the ASCII diagrams showing each merge case in
vma_merge_existing_range() to be clearer - the arrow range previously
showed the vmg->start, end spanned area, but it is clearer to change this
to show the final merged VMA.
This patch has no change in functional behaviour.
Link: https://lkml.kernel.org/r/cover.1738326519.git.lorenzo.stoakes@oracle.com
Link: https://lkml.kernel.org/r/4dfe60f1419d55e5d0516f56349695d73a57184c.1738326519.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
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Yosry Ahmed
|
6df8bae8e8 |
mm: zbud: remove zbud
The zbud compressed pages allocator is rarely used, most users use zsmalloc. zbud consumes much more memory (only stores 1 or 2 compressed pages per physical page). The only advantage of zbud is a marginal performance improvement that by no means justify the memory overhead. Historically, zsmalloc had significantly worse latency than zbud and z3fold but offered better memory savings. This is no longer the case as shown by a simple recent analysis [1]. In a kernel build test on tmpfs in a limited cgroup, zbud 2-3% less time than zsmalloc, but at the cost of using ~32% more memory (1.5G vs 1.13G). The tradeoff does not make sense for zbud in any practical scenario. The only alleged advantage of zbud is not having the dependency on CONFIG_MMU, but CONFIG_SWAP already depends on CONFIG_MMU anyway, and zbud is only used by zswap. Remove zbud after z3fold's removal, leaving zsmalloc as the one and only zpool allocator. Leave the removal of the zpool API (and its associated config options) to a followup cleanup after no more allocators show up. Deprecating zbud for a few cycles before removing it was initially proposed [2], like z3fold was marked as deprecated for 2 cycles [3]. However, Johannes rightfully pointed out that the 2 cycles is too short for most downstream consumers, and z3fold was deprecated first only as a courtesy anyway. [1]https://lore.kernel.org/lkml/CAJD7tkbRF6od-2x_L8-A1QL3=2Ww13sCj4S3i4bNndqF+3+_Vg@mail.gmail.com/ [2]https://lore.kernel.org/lkml/Z5gdnSX5Lv-nfjQL@google.com/ [3]https://lore.kernel.org/lkml/20240904233343.933462-1-yosryahmed@google.com/ Link: https://lkml.kernel.org/r/20250129180633.3501650-3-yosry.ahmed@linux.dev Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev> Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Nhat Pham <nphamcs@gmail.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vitaly Wool <vitaly.wool@konsulko.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: WANG Xuerui <kernel@xen0n.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Yosry Ahmed
|
58ba73e521 |
mm: z3fold: remove z3fold
Patch series "mm: zswap: remove z3fold and zbud", v2. After 2 cycles of deprecating z3fold, remove it as well as zbud (rationale in specific patches). This patch (of 2): Z3fold has been marked as deprecated for 2 cycles and no one complained, as expected. As there are no known users, remove the code now. Link: https://lkml.kernel.org/r/20250129180633.3501650-1-yosry.ahmed@linux.dev Link: https://lkml.kernel.org/r/20250129180633.3501650-2-yosry.ahmed@linux.dev Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Nhat Pham <nphamcs@gmail.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Chengming Zhou <chengming.zhou@linux.dev> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Dan Streetman <ddstreet@ieee.org> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vitaly Wool <vitaly.wool@konsulko.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: WANG Xuerui <kernel@xen0n.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Hao Zhang
|
350dce38eb |
mm/vmscan: extract calculated pressure balance as a function
Extract pressure balance calculation into a function.This doesn't change current behaviour. [akpm@linux-foundation.org: 80-col wrapping] Link: https://lkml.kernel.org/r/tencent_735DB36A2306C08B8568049E4C0B99716C07@qq.com Signed-off-by: Hao Zhang <zhanghao1@kylinos.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
b8932ca8b9 |
mm/rmap: avoid -EBUSY from make_device_exclusive()
Failing to obtain the folio lock, for example because the folio is concurrently getting migrated or swapped out, can easily make the callers fail: for example, the hmm selftest can sometimes be observed to fail because of this. Instead of forcing the caller to retry, let's simply retry in this to-be-expected case. Similarly, avoid spurious failures simply because we raced with someone (e.g., swapout) modifying the page table such that our folio_walk fails. Simply unconditionally lock the folio, and retry GUP if our folio_walk fails. Note that the folio_walk repeatedly failing is not something we expect. Note that we might want to avoid grabbing the folio lock at some point; for now, keep that as is and only unconditionally lock the folio. With this change, the hmm selftests don't fail simply because the folio is already locked. While this fixes the selftests in some cases, it's likely not something that deserves a "Fixes:". Link: https://lkml.kernel.org/r/20250210193801.781278-18-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
|
f495bd7e0d |
mm/rmap: keep mapcount untouched for device-exclusive entries
Now that conversion to device-exclusive does no longer perform an rmap
walk and all page_vma_mapped_walk() users were taught to properly handle
device-exclusive entries, let's treat device-exclusive entries just as if
they would be present, similar to how we handle device-private entries
already.
This fixes swapout/migration/split/hwpoison of folios with
device-exclusive entries.
We only had to take care of page_vma_mapped_walk() users, because these
traditionally assume pte_present(). Other page table walkers already have
to handle !pte_present(), and some of them might simply skip them (e.g.,
MADV_PAGEOUT) if they are not specialized on them. This change doesn't
modify the latter.
Note that while folios with device-exclusive PTEs can now get migrated,
khugepaged will not collapse a THP if there is device-exclusive PTE.
Doing so might also not be desired if the device frequently performs
atomics to the same page. Similarly, KSM will never merge order-0 folios
that are device-exclusive.
Link: https://lkml.kernel.org/r/20250210193801.781278-17-david@redhat.com
Fixes:
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David Hildenbrand
|
1f3ac4c577 |
mm/damon: handle device-exclusive entries correctly in damon_folio_mkold_one()
Ever since commit
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David Hildenbrand
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39628c39ba |
mm/damon: handle device-exclusive entries correctly in damon_folio_young_one()
Ever since commit |
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David Hildenbrand
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3faa3ebc89 |
mm/page_idle: handle device-exclusive entries correctly in page_idle_clear_pte_refs_one()
Ever since commit |
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David Hildenbrand
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bd1f2b2ace |
mm/rmap: handle device-exclusive entries correctly in page_vma_mkclean_one()
Ever since commit |
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David Hildenbrand
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bf983108be |
mm/rmap: handle device-exclusive entries correctly in try_to_migrate_one()
Ever since commit |
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David Hildenbrand
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6552929560 |
mm/rmap: handle device-exclusive entries correctly in try_to_unmap_one()
Ever since commit |
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David Hildenbrand
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789cfc6699 |
mm/ksm: handle device-exclusive entries correctly in write_protect_page()
Ever since commit |
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David Hildenbrand
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7b2e497a42 |
mm/page_vma_mapped: device-exclusive entries are not migration entries
It's unclear why they would be considered migration entries; they are not.
Likely we'll never really trigger that case in practice, because migration
(including folio split) of a folio that has device-exclusive entries is
never started, as we would detect "additional references":
device-exclusive entries adjust the mapcount, but not the refcount.
Link: https://lkml.kernel.org/r/20250210193801.781278-8-david@redhat.com
Fixes:
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David Hildenbrand
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c25465eb76 |
mm: use single SWP_DEVICE_EXCLUSIVE entry type
There is no need for the distinction anymore; let's merge the readable and writable device-exclusive entries into a single device-exclusive entry type. Link: https://lkml.kernel.org/r/20250210193801.781278-7-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Simona Vetter <simona.vetter@ffwll.ch> Reviewed-by: Alistair Popple <apopple@nvidia.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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9a91459214 |
mm/memory: detect writability in restore_exclusive_pte() through can_change_pte_writable()
Let's do it just like mprotect write-upgrade or during NUMA-hinting faults on PROT_NONE PTEs: detect if the PTE can be writable by using can_change_pte_writable(). Set the PTE only dirty if the folio is dirty: we might not necessarily have a write access, and setting the PTE writable doesn't require setting the PTE dirty. From a CPU perspective, these entries are clean. So only set the PTE dirty if the folios is dirty. With this change in place, there is no need to have separate readable and writable device-exclusive entry types, and we'll merge them next separately. Note that, during fork(), we first convert the device-exclusive entries back to ordinary PTEs, and we only ever allow conversion of writable PTEs to device-exclusive -- only mprotect can currently change them to readable-device-exclusive. Consequently, we always expect PageAnonExclusive(page)==true and can_change_pte_writable()==true, unless we are dealing with soft-dirty tracking or uffd-wp. But reusing can_change_pte_writable() for now is cleaner. Link: https://lkml.kernel.org/r/20250210193801.781278-6-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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438354724f |
mm/rmap: implement make_device_exclusive() using folio_walk instead of rmap walk
We require a writable PTE and only support anonymous folio: we can only have exactly one PTE pointing at that page, which we can just lookup using a folio walk, avoiding the rmap walk and the anon VMA lock. So let's stop doing an rmap walk and perform a folio walk instead, so we can easily just modify a single PTE and avoid relying on rmap/mapcounts. We now effectively work on a single PTE instead of multiple PTEs of a large folio, allowing for conversion of individual PTEs from non-exclusive to device-exclusive -- note that the opposite direction always works on single PTEs: restore_exclusive_pte(). With this change, device-exclusive handling is fully compatible with THPs / large folios. We still require PMD-sized THPs to get PTE-mapped, and supporting PMD-mapped THP (without the PTE-remapping) is a different endeavour that might not be worth it at this point: it might even have negative side-effects [1]. This gets rid of the "folio_mapcount()" usage and let's us fix ordinary rmap walks (migration/swapout) next. Spell out that messing with the mapcount is wrong and must be fixed. [1] https://lkml.kernel.org/r/Z5tI-cOSyzdLjoe_@phenom.ffwll.local Link: https://lkml.kernel.org/r/20250210193801.781278-5-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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599b684a78 |
mm/rmap: convert make_device_exclusive_range() to make_device_exclusive()
The single "real" user in the tree of make_device_exclusive_range() always requests making only a single address exclusive. The current implementation is hard to fix for properly supporting anonymous THP / large folios and for avoiding messing with rmap walks in weird ways. So let's always process a single address/page and return folio + page to minimize page -> folio lookups. This is a preparation for further changes. Reject any non-anonymous or hugetlb folios early, directly after GUP. While at it, extend the documentation of make_device_exclusive() to clarify some things. Link: https://lkml.kernel.org/r/20250210193801.781278-4-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Acked-by: Simona Vetter <simona.vetter@ffwll.ch> Reviewed-by: Alistair Popple <apopple@nvidia.com> Tested-by: Alistair Popple <apopple@nvidia.com> Cc: Alex Shi <alexs@kernel.org> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Dave Airlie <airlied@gmail.com> Cc: Jann Horn <jannh@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Karol Herbst <kherbst@redhat.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: Lyude <lyude@redhat.com> Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: SeongJae Park <sj@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Yanteng Si <si.yanteng@linux.dev> Cc: Barry Song <v-songbaohua@oppo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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David Hildenbrand
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bc3fe6805c |
mm/rmap: reject hugetlb folios in folio_make_device_exclusive()
Even though FOLL_SPLIT_PMD on hugetlb now always fails with -EOPNOTSUPP, let's add a safety net in case FOLL_SPLIT_PMD usage would ever be reworked. In particular, before commit |
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David Hildenbrand
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8977752c80 |
mm/gup: reject FOLL_SPLIT_PMD with hugetlb VMAs
Patch series "mm: fixes for device-exclusive entries (hmm)", v2.
Discussing the PageTail() call in make_device_exclusive_range() with
Willy, I recently discovered [1] that device-exclusive handling does not
properly work with THP, making the hmm-tests selftests fail if THPs are
enabled on the system.
Looking into more details, I found that hugetlb is not properly fenced,
and I realized that something that was bugging me for longer -- how
device-exclusive entries interact with mapcounts -- completely breaks
migration/swapout/split/hwpoison handling of these folios while they have
device-exclusive PTEs.
The program below can be used to allocate 1 GiB worth of pages and making
them device-exclusive on a kernel with CONFIG_TEST_HMM.
Once they are device-exclusive, these folios cannot get swapped out
(proc$pid/smaps_rollup will always indicate 1 GiB RSS no matter how much
one forces memory reclaim), and when having a memory block onlined to
ZONE_MOVABLE, trying to offline it will loop forever and complain about
failed migration of a page that should be movable.
# echo offline > /sys/devices/system/memory/memory136/state
# echo online_movable > /sys/devices/system/memory/memory136/state
# ./hmm-swap &
... wait until everything is device-exclusive
# echo offline > /sys/devices/system/memory/memory136/state
[ 285.193431][T14882] page: refcount:2 mapcount:0 mapping:0000000000000000
index:0x7f20671f7 pfn:0x442b6a
[ 285.196618][T14882] memcg:ffff888179298000
[ 285.198085][T14882] anon flags: 0x5fff0000002091c(referenced|uptodate|
dirty|active|owner_2|swapbacked|node=1|zone=3|lastcpupid=0x7ff)
[ 285.201734][T14882] raw: ...
[ 285.204464][T14882] raw: ...
[ 285.207196][T14882] page dumped because: migration failure
[ 285.209072][T14882] page_owner tracks the page as allocated
[ 285.210915][T14882] page last allocated via order 0, migratetype
Movable, gfp_mask 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO),
id 14926, tgid 14926 (hmm-swap), ts 254506295376, free_ts 227402023774
[ 285.216765][T14882] post_alloc_hook+0x197/0x1b0
[ 285.218874][T14882] get_page_from_freelist+0x76e/0x3280
[ 285.220864][T14882] __alloc_frozen_pages_noprof+0x38e/0x2740
[ 285.223302][T14882] alloc_pages_mpol+0x1fc/0x540
[ 285.225130][T14882] folio_alloc_mpol_noprof+0x36/0x340
[ 285.227222][T14882] vma_alloc_folio_noprof+0xee/0x1a0
[ 285.229074][T14882] __handle_mm_fault+0x2b38/0x56a0
[ 285.230822][T14882] handle_mm_fault+0x368/0x9f0
...
This series fixes all issues I found so far. There is no easy way to fix
without a bigger rework/cleanup. I have a bunch of cleanups on top (some
previous sent, some the result of the discussion in v1) that I will send
out separately once this landed and I get to it.
I wish we could just use some special present PROT_NONE PTEs instead of
these (non-present, non-none) fake-swap entries; but that just results in
the same problem we keep having (lack of spare PTE bits), and staring at
other similar fake-swap entries, that ship has sailed.
With this series, make_device_exclusive() doesn't actually belong into
mm/rmap.c anymore, but I'll leave moving that for another day.
I only tested this series with the hmm-tests selftests due to lack of HW,
so I'd appreciate some testing, especially if the interaction between two
GPUs wanting a device-exclusive entry works as expected.
<program>
#include <stdio.h>
#include <fcntl.h>
#include <stdint.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/ioctl.h>
#define HMM_DMIRROR_EXCLUSIVE _IOWR('H', 0x05, struct hmm_dmirror_cmd)
struct hmm_dmirror_cmd {
__u64 addr;
__u64 ptr;
__u64 npages;
__u64 cpages;
__u64 faults;
};
const size_t size = 1 * 1024 * 1024 * 1024ul;
const size_t chunk_size = 2 * 1024 * 1024ul;
int main(void)
{
struct hmm_dmirror_cmd cmd;
size_t cur_size;
int fd, ret;
char *addr, *mirror;
fd = open("/dev/hmm_dmirror1", O_RDWR, 0);
if (fd < 0) {
perror("open failed\n");
exit(1);
}
addr = mmap(NULL, size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (addr == MAP_FAILED) {
perror("mmap failed\n");
exit(1);
}
madvise(addr, size, MADV_NOHUGEPAGE);
memset(addr, 1, size);
mirror = malloc(chunk_size);
for (cur_size = 0; cur_size < size; cur_size += chunk_size) {
cmd.addr = (uintptr_t)addr + cur_size;
cmd.ptr = (uintptr_t)mirror;
cmd.npages = chunk_size / getpagesize();
ret = ioctl(fd, HMM_DMIRROR_EXCLUSIVE, &cmd);
if (ret) {
perror("ioctl failed\n");
exit(1);
}
}
pause();
return 0;
}
</program>
[1] https://lkml.kernel.org/r/25e02685-4f1d-47fa-be5b-01ff85bb0ce2@redhat.com
This patch (of 17):
We only have two FOLL_SPLIT_PMD users. While uprobe refuses hugetlb
early, make_device_exclusive_range() can end up getting called on hugetlb
VMAs.
Right now, this means that with a PMD-sized hugetlb page, we can end up
calling split_huge_pmd(), because pmd_trans_huge() also succeeds with
hugetlb PMDs.
For example, using a modified hmm-test selftest one can trigger:
[ 207.017134][T14945] ------------[ cut here ]------------
[ 207.018614][T14945] kernel BUG at mm/page_table_check.c:87!
[ 207.019716][T14945] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
[ 207.021072][T14945] CPU: 3 UID: 0 PID: ...
[ 207.023036][T14945] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014
[ 207.024834][T14945] RIP: 0010:page_table_check_clear.part.0+0x488/0x510
[ 207.026128][T14945] Code: ...
[ 207.029965][T14945] RSP: 0018:ffffc9000cb8f348 EFLAGS: 00010293
[ 207.031139][T14945] RAX: 0000000000000000 RBX: 00000000ffffffff RCX: ffffffff8249a0cd
[ 207.032649][T14945] RDX: ffff88811e883c80 RSI: ffffffff8249a357 RDI: ffff88811e883c80
[ 207.034183][T14945] RBP: ffff888105c0a050 R08: 0000000000000005 R09: 0000000000000000
[ 207.035688][T14945] R10: 00000000ffffffff R11: 0000000000000003 R12: 0000000000000001
[ 207.037203][T14945] R13: 0000000000000200 R14: 0000000000000001 R15: dffffc0000000000
[ 207.038711][T14945] FS: 00007f2783275740(0000) GS:ffff8881f4980000(0000) knlGS:0000000000000000
[ 207.040407][T14945] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 207.041660][T14945] CR2: 00007f2782c00000 CR3: 0000000132356000 CR4: 0000000000750ef0
[ 207.043196][T14945] PKRU: 55555554
[ 207.043880][T14945] Call Trace:
[ 207.044506][T14945] <TASK>
[ 207.045086][T14945] ? __die+0x51/0x92
[ 207.045864][T14945] ? die+0x29/0x50
[ 207.046596][T14945] ? do_trap+0x250/0x320
[ 207.047430][T14945] ? do_error_trap+0xe7/0x220
[ 207.048346][T14945] ? page_table_check_clear.part.0+0x488/0x510
[ 207.049535][T14945] ? handle_invalid_op+0x34/0x40
[ 207.050494][T14945] ? page_table_check_clear.part.0+0x488/0x510
[ 207.051681][T14945] ? exc_invalid_op+0x2e/0x50
[ 207.052589][T14945] ? asm_exc_invalid_op+0x1a/0x20
[ 207.053596][T14945] ? page_table_check_clear.part.0+0x1fd/0x510
[ 207.054790][T14945] ? page_table_check_clear.part.0+0x487/0x510
[ 207.055993][T14945] ? page_table_check_clear.part.0+0x488/0x510
[ 207.057195][T14945] ? page_table_check_clear.part.0+0x487/0x510
[ 207.058384][T14945] __page_table_check_pmd_clear+0x34b/0x5a0
[ 207.059524][T14945] ? __pfx___page_table_check_pmd_clear+0x10/0x10
[ 207.060775][T14945] ? __pfx___mutex_unlock_slowpath+0x10/0x10
[ 207.061940][T14945] ? __pfx___lock_acquire+0x10/0x10
[ 207.062967][T14945] pmdp_huge_clear_flush+0x279/0x360
[ 207.064024][T14945] split_huge_pmd_locked+0x82b/0x3750
...
Before commit
|
||
|
Zi Yan
|
9b2f764933 |
mm/huge_memory: allow split shmem large folio to any lower order
Commit 4d684b5f92ba ("mm: shmem: add large folio support for tmpfs") has
added large folio support to shmem. Remove the restriction in
split_huge_page*().
Link: https://lkml.kernel.org/r/20250122161928.1240637-2-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Yang Shi <yang@os.amperecomputing.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shuemov <kirill.shutemov@linux.intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
||
|
Carlos Llamas
|
5f6084f95b |
mm/oom_kill: fix trivial typo in comment
Update 'give' -> 'given' in the description of oom_reap_task_mm(). Link: https://lkml.kernel.org/r/20250123193523.1496909-1-cmllamas@google.com Signed-off-by: Carlos Llamas <cmllamas@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Johannes Weiner
|
89ce924f0b |
mm: memcontrol: move memsw charge callbacks to v1
The interweaving of two entirely different swap accounting strategies has been one of the more confusing parts of the memcg code. Split out the v1 code to clarify the implementation and a handful of callsites, and to avoid building the v1 bits when !CONFIG_MEMCG_V1. text data bss dec hex filename 39253 6446 4160 49859 c2c3 mm/memcontrol.o.old 38877 6382 4160 49419 c10b mm/memcontrol.o Link: https://lkml.kernel.org/r/20250124054132.45643-1-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Balbir Singh <balbirs@nvidia.com> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Cc: Muchun Song <muchun.song@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Johannes Weiner
|
0d892bbbfa |
mm: memcontrol: move stray ratelimit bits to v1
|
||
|
Johannes Weiner
|
75fe8ec238 |
mm: memcontrol: unshare v2-only charge API bits again
|
||
|
Chen Ridong
|
610dc18c50 |
memcg: add CONFIG_MEMCG_V1 for 'local' functions
Add CONFIG_MEMCG_V1 for the 'local' functions, which are only used in memcg v1, so that they won't be built for v2. Link: https://lkml.kernel.org/r/20250124073514.2375622-5-chenridong@huaweicloud.com Signed-off-by: Chen Ridong <chenridong@huawei.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Cc: David Finkel <davidf@vimeo.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Wang Weiyang <wangweiyang2@huawei.com> Cc: Yosry Ahmed <yosryahmed@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Michal Koutný <mkoutny@suse.com> Cc: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Chen Ridong
|
bc812d1905 |
memcg: factor out the replace_stock_objcg function
Factor out the 'replace_stock_objcg' function to make the code more cohesive. Link: https://lkml.kernel.org/r/20250124073514.2375622-4-chenridong@huaweicloud.com Signed-off-by: Chen Ridong <chenridong@huawei.com> Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: David Finkel <davidf@vimeo.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Michal Koutný <mkoutny@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Wang Weiyang <wangweiyang2@huawei.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Chen Ridong
|
2059c8e320 |
memcg: call the free function when allocation of pn fails
The 'free_mem_cgroup_per_node_info' function is used to free the 'mem_cgroup_per_node' struct. Using 'pn' as the input for the free_mem_cgroup_per_node_info function will be much clearer. Call 'free_mem_cgroup_per_node_info' when 'alloc_mem_cgroup_per_node_info' fails, to free 'pn' as a whole, which makes the code more cohesive. Link: https://lkml.kernel.org/r/20250124073514.2375622-3-chenridong@huaweicloud.com Signed-off-by: Chen Ridong <chenridong@huawei.com> Reviewed-by: Michal Koutný <mkoutny@suse.com> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Cc: David Finkel <davidf@vimeo.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Wang Weiyang <wangweiyang2@huawei.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Chen Ridong
|
1c81f1a699 |
memcg: use OFP_PEAK_UNSET instead of -1
Patch series "Some cleanup for memcg", v4. This patch (of 4): The 'OFP_PEAK_UNSET' has been defined, use it instead of '-1'. Link: https://lkml.kernel.org/r/20250124073514.2375622-1-chenridong@huaweicloud.com Link: https://lkml.kernel.org/r/20250124073514.2375622-2-chenridong@huaweicloud.com Signed-off-by: Chen Ridong <chenridong@huawei.com> Reviewed-by: Michal Koutný <mkoutny@suse.com> Acked-by: David Finkel <davidf@vimeo.com> Acked-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Roman Gushchin <roman.gushchin@linux.dev> Cc: Michal Hocko <mhocko@suse.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Muchun Song <muchun.song@linux.dev> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Wang Weiyang <wangweiyang2@huawei.com> Cc: Yosry Ahmed <yosryahmed@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|
Kirill A. Shutemov
|
800f1059c9 |
mm/page_alloc: fix memory accept before watermarks gets initialized
Watermarks are initialized during the postcore initcall. Until then, all
watermarks are set to zero. This causes cond_accept_memory() to
incorrectly skip memory acceptance because a watermark of 0 is always met.
This can lead to a premature OOM on boot.
To ensure progress, accept one MAX_ORDER page if the watermark is zero.
Link: https://lkml.kernel.org/r/20250310082855.2587122-1-kirill.shutemov@linux.intel.com
Fixes:
|
||
|
Shakeel Butt
|
9f01b49544 |
memcg: drain obj stock on cpu hotplug teardown
Currently on cpu hotplug teardown, only memcg stock is drained but we
need to drain the obj stock as well otherwise we will miss the stats
accumulated on the target cpu as well as the nr_bytes cached. The stats
include MEMCG_KMEM, NR_SLAB_RECLAIMABLE_B & NR_SLAB_UNRECLAIMABLE_B. In
addition we are leaking reference to struct obj_cgroup object.
Link: https://lkml.kernel.org/r/20250310230934.2913113-1-shakeel.butt@linux.dev
Fixes:
|
||
|
Zi Yan
|
14efb47935 |
mm/huge_memory: drop beyond-EOF folios with the right number of refs
When an after-split folio is large and needs to be dropped due to EOF,
folio_put_refs(folio, folio_nr_pages(folio)) should be used to drop all
page cache refs. Otherwise, the folio will not be freed, causing memory
leak.
This leak would happen on a filesystem with blocksize > page_size and a
truncate is performed, where the blocksize makes folios split to >0 order
ones, causing truncated folios not being freed.
Link: https://lkml.kernel.org/r/20250310155727.472846-1-ziy@nvidia.com
Fixes:
|
||
|
Raphael S. Carvalho
|
182db972c9 |
mm: fix error handling in __filemap_get_folio() with FGP_NOWAIT
original report: https://lore.kernel.org/all/CAKhLTr1UL3ePTpYjXOx2AJfNk8Ku2EdcEfu+CH1sf3Asr=B-Dw@mail.gmail.com/T/ When doing buffered writes with FGP_NOWAIT, under memory pressure, the system returned ENOMEM despite there being plenty of available memory, to be reclaimed from page cache. The user space used io_uring interface, which in turn submits I/O with FGP_NOWAIT (the fast path). retsnoop pointed to iomap_get_folio: 00:34:16.180612 -> 00:34:16.180651 TID/PID 253786/253721 (reactor-1/combined_tests): entry_SYSCALL_64_after_hwframe+0x76 do_syscall_64+0x82 __do_sys_io_uring_enter+0x265 io_submit_sqes+0x209 io_issue_sqe+0x5b io_write+0xdd xfs_file_buffered_write+0x84 iomap_file_buffered_write+0x1a6 32us [-ENOMEM] iomap_write_begin+0x408 iter=&{.inode=0xffff8c67aa031138,.len=4096,.flags=33,.iomap={.addr=0xffffffffffffffff,.length=4096,.type=1,.flags=3,.bdev=0x… pos=0 len=4096 foliop=0xffffb32c296b7b80 ! 4us [-ENOMEM] iomap_get_folio iter=&{.inode=0xffff8c67aa031138,.len=4096,.flags=33,.iomap={.addr=0xffffffffffffffff,.length=4096,.type=1,.flags=3,.bdev=0x… pos=0 len=4096 This is likely a regression caused by |
||
|
Muchun Song
|
73f839b6d2 |
mm: memcontrol: fix swap counter leak from offline cgroup
Commit |
||
|
Dev Jain
|
8c6ff7f181 |
mm/vma: do not register private-anon mappings with khugepaged during mmap
We already are registering private-anon VMAs with khugepaged during fault
time, in do_huge_pmd_anonymous_page(). Commit "register suitable readonly
file vmas for khugepaged" moved the khugepaged registration logic from
shmem_mmap to the generic mmap path.
The userspace-visible effect should be this: khugepaged will unnecessarily
scan mm's which haven't yet faulted in. Note that it won't actually
collapse because all PTEs are none.
Now that I think about it, the mm is going to have a file VMA anyways
during fork+exec, so the mm already gets registered during mmap due to the
non-anon case (I *think*), so at least one of either the mmap registration
or fault-time registration is redundant.
Make this logic specific for non-anon mappings.
Link: https://lkml.kernel.org/r/20250306063037.16299-1-dev.jain@arm.com
Fixes:
|
||
|
Zi Yan
|
60cf233b58 |
mm/migrate: fix shmem xarray update during migration
A shmem folio can be either in page cache or in swap cache, but not at the
same time. Namely, once it is in swap cache, folio->mapping should be
NULL, and the folio is no longer in a shmem mapping.
In __folio_migrate_mapping(), to determine the number of xarray entries to
update, folio_test_swapbacked() is used, but that conflates shmem in page
cache case and shmem in swap cache case. It leads to xarray multi-index
entry corruption, since it turns a sibling entry to a normal entry during
xas_store() (see [1] for a userspace reproduction). Fix it by only using
folio_test_swapcache() to determine whether xarray is storing swap cache
entries or not to choose the right number of xarray entries to update.
[1] https://lore.kernel.org/linux-mm/Z8idPCkaJW1IChjT@casper.infradead.org/
Note:
In __split_huge_page(), folio_test_anon() && folio_test_swapcache() is
used to get swap_cache address space, but that ignores the shmem folio in
swap cache case. It could lead to NULL pointer dereferencing when a
in-swap-cache shmem folio is split at __xa_store(), since
!folio_test_anon() is true and folio->mapping is NULL. But fortunately,
its caller split_huge_page_to_list_to_order() bails out early with EBUSY
when folio->mapping is NULL. So no need to take care of it here.
Link: https://lkml.kernel.org/r/20250305200403.2822855-1-ziy@nvidia.com
Fixes:
|
||
|
Jinjiang Tu
|
cb402bbdab |
mm/hugetlb: fix surplus pages in dissolve_free_huge_page()
In dissolve_free_huge_page(), free huge pages are dissolved without
adjusting surplus count. However, free huge pages may be accounted as
surplus pages, and will lead to wrong surplus count.
I reproduce this issue on qemu. The steps are:
1) Node1 is memory-less at first. Hot-add memory to node1 by executing
the two commands in qemu monitor:
object_add memory-backend-ram,id=mem1,size=1G
device_add pc-dimm,id=dimm1,memdev=mem1,node=1
2) online one memory block of Node1 with：
echo online_movable > /sys/devices/system/node/node1/memoryX/state
3) create 64 huge pages for node1
4) run a program to reserve (don't consume) all the huge pages
5) echo 0 > nr_huge_pages for node1. After this step, free huge pages in
Node1 are surplus.
6) create 80 huge pages for node0
7) offline memory of node1, The memory range to offline contains the free
surplus huge pages created in step3) ~ step5)
echo offline > /sys/devices/system/node/node1/memoryX/state
8) kill the program in step 4)
The result:
Node0 Node1
total 80 0
free 80 0
surplus 0 61
To fix it, adjust surplus when destroying huge pages if the node has
surplus pages in dissolve_free_hugetlb_folio().
The result with this patch:
Node0 Node1
total 80 0
free 80 0
surplus 0 0
Link: https://lkml.kernel.org/r/20250304132106.2872754-1-tujinjiang@huawei.com
Fixes:
|
||
|
SeongJae Park
|
73d7a69de2 |
mm/damon/core: initialize damos->walk_completed in damon_new_scheme()
The function for allocating and initialize a 'struct damos' object,
damon_new_scheme(), is not initializing damos->walk_completed field. Only
damos_walk_complete() is setting the field. Hence the field will be
eventually set and used correctly from second damos_walk() call for the
scheme. But the first damos_walk() could mistakenly not walk on the
regions. Actually, a common usage of DAMOS for taking an access pattern
snapshot is installing a monitoring-purpose DAMOS scheme, doing
damos_walk() to retrieve the snapshot, and then removing the scheme.
DAMON user-space tool (damo) also gets runtime snapshot in the way. Hence
the problem can continuously happen in such use cases. Initialize it
properly in the allocation function.
Link: https://lkml.kernel.org/r/20250228174450.41472-1-sj@kernel.org
Fixes:
|
||
|
SeongJae Park
|
39a326e6da |
mm/damon: respect core layer filters' allowance decision on ops layer
Filtering decisions are made in filters evaluation order. Once a decision
is made by a filter, filters that scheduled to be evaluated after the
decision-made filter should just respect it. This is the intended and
documented behavior. Since core layer-handled filters are evaluated
before operations layer-handled filters, decisions made on core layer
should respected by ops layer.
In case of reject filters, the decision is respected, since core
layer-rejected regions are not passed to ops layer. But in case of allow
filters, ops layer filters don't know if the region has passed to them
because it was allowed by core filters or just because it didn't match to
any core layer. The current wrong implementation assumes it was due to
not matched by any core filters. As a reuslt, the decision is not
respected. Pass the missing information to ops layer using a new filed in
'struct damos', and make the ops layer filters respect it.
Link: https://lkml.kernel.org/r/20250228175336.42781-1-sj@kernel.org
Fixes:
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Dave Hansen
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665575cff0 |
filemap: move prefaulting out of hot write path
There is a generic anti-pattern that shows up in the VFS and several filesystems where the hot write paths touch userspace twice when they could get away with doing it once. Dave Chinner suggested that they should all be fixed up[1]. I agree[2]. But, the series to do that fixup spans a bunch of filesystems and a lot of people. This patch fixes common code that absolutely everyone uses. It has measurable performance benefits[3]. I think this patch can go in and not be held up by the others. I will post them separately to their separate maintainers for consideration. But, honestly, I'm not going to lose any sleep if the maintainers don't pick those up. 1. https://lore.kernel.org/all/Z5f-x278Z3wTIugL@dread.disaster.area/ 2. https://lore.kernel.org/all/20250129181749.C229F6F3@davehans-spike.ostc.intel.com/ 3. https://lore.kernel.org/all/202502121529.d62a409e-lkp@intel.com/ This patch: There is a bit of a sordid history here. I originally wrote |
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Linus Torvalds
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1110ce6a1e |
Merge tag 'mm-hotfixes-stable-2025-03-08-16-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc fixes from Andrew Morton:
"33 hotfixes. 24 are cc:stable and the remainder address post-6.13
issues or aren't considered necessary for -stable kernels.
26 are for MM and 7 are for non-MM.
- "mm: memory_failure: unmap poisoned folio during migrate properly"
from Ma Wupeng fixes a couple of two year old bugs involving the
migration of hwpoisoned folios.
- "selftests/damon: three fixes for false results" from SeongJae Park
fixes three one year old bugs in the SAMON selftest code.
The remainder are singletons and doubletons. Please see the individual
changelogs for details"
* tag 'mm-hotfixes-stable-2025-03-08-16-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (33 commits)
mm/page_alloc: fix uninitialized variable
rapidio: add check for rio_add_net() in rio_scan_alloc_net()
rapidio: fix an API misues when rio_add_net() fails
MAINTAINERS: .mailmap: update Sumit Garg's email address
Revert "mm/page_alloc.c: don't show protection in zone's ->lowmem_reserve[] for empty zone"
mm: fix finish_fault() handling for large folios
mm: don't skip arch_sync_kernel_mappings() in error paths
mm: shmem: remove unnecessary warning in shmem_writepage()
userfaultfd: fix PTE unmapping stack-allocated PTE copies
userfaultfd: do not block on locking a large folio with raised refcount
mm: zswap: use ATOMIC_LONG_INIT to initialize zswap_stored_pages
mm: shmem: fix potential data corruption during shmem swapin
mm: fix kernel BUG when userfaultfd_move encounters swapcache
selftests/damon/damon_nr_regions: sort collected regiosn before checking with min/max boundaries
selftests/damon/damon_nr_regions: set ops update for merge results check to 100ms
selftests/damon/damos_quota: make real expectation of quota exceeds
include/linux/log2.h: mark is_power_of_2() with __always_inline
NFS: fix nfs_release_folio() to not deadlock via kcompactd writeback
mm, swap: avoid BUG_ON in relocate_cluster()
mm: swap: use correct step in loop to wait all clusters in wait_for_allocation()
...
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Linus Torvalds
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21e4543a2e |
Merge tag 'slab-for-6.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab
Pull slab fix from Vlastimil Babka: - Stable fix for kmem_cache_destroy() called from a WQ_MEM_RECLAIM workqueue causing a warning due to the new kvfree_rcu_barrier() (Uladzislau Rezki) * tag 'slab-for-6.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab: mm/slab/kvfree_rcu: Switch to WQ_MEM_RECLAIM wq |
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Linus Torvalds
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00a7d39898 |
fs/pipe: add simpler helpers for common cases
The fix to atomically read the pipe head and tail state when not holding
the pipe mutex has caused a number of headaches due to the size change
of the involved types.
It turns out that we don't have _that_ many places that access these
fields directly and were affected, but we have more than we strictly
should have, because our low-level helper functions have been designed
to have intimate knowledge of how the pipes work.
And as a result, that random noise of direct 'pipe->head' and
'pipe->tail' accesses makes it harder to pinpoint any actual potential
problem spots remaining.
For example, we didn't have a "is the pipe full" helper function, but
instead had a "given these pipe buffer indexes and this pipe size, is
the pipe full". That's because some low-level pipe code does actually
want that much more complicated interface.
But most other places literally just want a "is the pipe full" helper,
and not having it meant that those places ended up being unnecessarily
much too aware of this all.
It would have been much better if only the very core pipe code that
cared had been the one aware of this all.
So let's fix it - better late than never. This just introduces the
trivial wrappers for "is this pipe full or empty" and to get how many
pipe buffers are used, so that instead of writing
if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
the places that literally just want to know if a pipe is full can just
say
if (pipe_is_full(pipe))
instead. The existing trivial cases were converted with a 'sed' script.
This cuts down on the places that access pipe->head and pipe->tail
directly outside of the pipe code (and core splice code) quite a lot.
The splice code in particular still revels in doing the direct low-level
accesses, and the fuse fuse_dev_splice_write() code also seems a bit
unnecessarily eager to go very low-level, but it's at least a bit better
than it used to be.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Hao Zhang
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8fe9ed44dc |
mm/page_alloc: fix uninitialized variable
The variable "compact_result" is not initialized in function __alloc_pages_slowpath(). It causes should_compact_retry() to use an uninitialized value. Initialize variable "compact_result" with the value COMPACT_SKIPPED. BUG: KMSAN: uninit-value in __alloc_pages_slowpath+0xee8/0x16c0 mm/page_alloc.c:4416 __alloc_pages_slowpath+0xee8/0x16c0 mm/page_alloc.c:4416 __alloc_frozen_pages_noprof+0xa4c/0xe00 mm/page_alloc.c:4752 alloc_pages_mpol+0x4cd/0x890 mm/mempolicy.c:2270 alloc_frozen_pages_noprof mm/mempolicy.c:2341 [inline] alloc_pages_noprof mm/mempolicy.c:2361 [inline] folio_alloc_noprof+0x1dc/0x350 mm/mempolicy.c:2371 filemap_alloc_folio_noprof+0xa6/0x440 mm/filemap.c:1019 __filemap_get_folio+0xb9a/0x1840 mm/filemap.c:1970 grow_dev_folio fs/buffer.c:1039 [inline] grow_buffers fs/buffer.c:1105 [inline] __getblk_slow fs/buffer.c:1131 [inline] bdev_getblk+0x2c9/0xab0 fs/buffer.c:1431 getblk_unmovable include/linux/buffer_head.h:369 [inline] ext4_getblk+0x3b7/0xe50 fs/ext4/inode.c:864 ext4_bread_batch+0x9f/0x7d0 fs/ext4/inode.c:933 __ext4_find_entry+0x1ebb/0x36c0 fs/ext4/namei.c:1627 ext4_lookup_entry fs/ext4/namei.c:1729 [inline] ext4_lookup+0x189/0xb40 fs/ext4/namei.c:1797 __lookup_slow+0x538/0x710 fs/namei.c:1793 lookup_slow+0x6a/0xd0 fs/namei.c:1810 walk_component fs/namei.c:2114 [inline] link_path_walk+0xf29/0x1420 fs/namei.c:2479 path_openat+0x30f/0x6250 fs/namei.c:3985 do_filp_open+0x268/0x600 fs/namei.c:4016 do_sys_openat2+0x1bf/0x2f0 fs/open.c:1428 do_sys_open fs/open.c:1443 [inline] __do_sys_openat fs/open.c:1459 [inline] __se_sys_openat fs/open.c:1454 [inline] __x64_sys_openat+0x2a1/0x310 fs/open.c:1454 x64_sys_call+0x36f5/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:258 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Local variable compact_result created at: __alloc_pages_slowpath+0x66/0x16c0 mm/page_alloc.c:4218 __alloc_frozen_pages_noprof+0xa4c/0xe00 mm/page_alloc.c:4752 Link: https://lkml.kernel.org/r/tencent_ED1032321D6510B145CDBA8CBA0093178E09@qq.com Reported-by: syzbot+0cfd5e38e96a5596f2b6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=0cfd5e38e96a5596f2b6 Signed-off-by: Hao Zhang <zhanghao1@kylinos.cn> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Michal Hocko <mhocko@kernel.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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Gabriel Krisman Bertazi
|
eae116d1f0 |
Revert "mm/page_alloc.c: don't show protection in zone's ->lowmem_reserve[] for empty zone"
Commit |
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Brian Geffon
|
34b82f33cf |
mm: fix finish_fault() handling for large folios
When handling faults for anon shmem finish_fault() will attempt to install
ptes for the entire folio. Unfortunately if it encounters a single
non-pte_none entry in that range it will bail, even if the pte that
triggered the fault is still pte_none. When this situation happens the
fault will be retried endlessly never making forward progress.
This patch fixes this behavior and if it detects that a pte in the range
is not pte_none it will fall back to setting a single pte.
[bgeffon@google.com: tweak whitespace]
Link: https://lkml.kernel.org/r/20250227133236.1296853-1-bgeffon@google.com
Link: https://lkml.kernel.org/r/20250226162341.915535-1-bgeffon@google.com
Fixes:
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Ryan Roberts
|
3685024edd |
mm: don't skip arch_sync_kernel_mappings() in error paths
Fix callers that previously skipped calling arch_sync_kernel_mappings() if an error occurred during a pgtable update. The call is still required to sync any pgtable updates that may have occurred prior to hitting the error condition. These are theoretical bugs discovered during code review. Link: https://lkml.kernel.org/r/20250226121610.2401743-1-ryan.roberts@arm.com Fixes: |
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Ricardo Cañuelo Navarro
|
adae46ac1e |
mm: shmem: remove unnecessary warning in shmem_writepage()
Although the scenario where shmem_writepage() is called with info->flags &
VM_LOCKED is unlikely to happen, it's still possible, as evidenced by
syzbot [1]. However, the warning in this case isn't necessary because the
situation is already handled correctly [2].
[2] https://lore.kernel.org/lkml/8afe1f7f-31a2-4fc0-1fbd-f9ba8a116fe3@google.com/
Link: https://lkml.kernel.org/r/20250226-20250221-warning-in-shmem_writepage-v1-1-5ad19420e17e@igalia.com
Fixes:
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||
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Suren Baghdasaryan
|
927e926d72 |
userfaultfd: fix PTE unmapping stack-allocated PTE copies
Current implementation of move_pages_pte() copies source and destination
PTEs in order to detect concurrent changes to PTEs involved in the move.
However these copies are also used to unmap the PTEs, which will fail if
CONFIG_HIGHPTE is enabled because the copies are allocated on the stack.
Fix this by using the actual PTEs which were kmap()ed.
Link: https://lkml.kernel.org/r/20250226185510.2732648-3-surenb@google.com
Fixes:
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||
|
Suren Baghdasaryan
|
37b338eed1 |
userfaultfd: do not block on locking a large folio with raised refcount
Lokesh recently raised an issue about UFFDIO_MOVE getting into a deadlock
state when it goes into split_folio() with raised folio refcount.
split_folio() expects the reference count to be exactly mapcount +
num_pages_in_folio + 1 (see can_split_folio()) and fails with EAGAIN
otherwise.
If multiple processes are trying to move the same large folio, they raise
the refcount (all tasks succeed in that) then one of them succeeds in
locking the folio, while others will block in folio_lock() while keeping
the refcount raised. The winner of this race will proceed with calling
split_folio() and will fail returning EAGAIN to the caller and unlocking
the folio. The next competing process will get the folio locked and will
go through the same flow. In the meantime the original winner will be
retried and will block in folio_lock(), getting into the queue of waiting
processes only to repeat the same path. All this results in a livelock.
An easy fix would be to avoid waiting for the folio lock while holding
folio refcount, similar to madvise_free_huge_pmd() where folio lock is
acquired before raising the folio refcount. Since we lock and take a
refcount of the folio while holding the PTE lock, changing the order of
these operations should not break anything.
Modify move_pages_pte() to try locking the folio first and if that fails
and the folio is large then return EAGAIN without touching the folio
refcount. If the folio is single-page then split_folio() is not called,
so we don't have this issue. Lokesh has a reproducer [1] and I verified
that this change fixes the issue.
[1] https://github.com/lokeshgidra/uffd_move_ioctl_deadlock
[akpm@linux-foundation.org: reflow comment to 80 cols, s/end/end up/]
Link: https://lkml.kernel.org/r/20250226185510.2732648-2-surenb@google.com
Fixes:
|