When vma_iter_prealloc() fails in do_mmap(), it jumps to error_just_free
as a error path of this function, but there are several possible issues.
1) It jumps to error_just_free without updating ret to -ENOMEM, meaning
do_mmap() will return 0 on failure.
2) The error path unconditionally frees the region struct. Since the
region was already added to the global nommu_region_tree via
add_nommu_region(), leaving it makes a potential dangling pointer in
the tree and may cause a use-after-free on the next tree walk.
3) If do_mmap() finds an existing overlapping shared region, it
increments its usage, sets region to this existing pregion, and jumps
to share:
region = pregion;
result = start;
goto share;
When vma_iter_prealloc() fails and jumps to error_just_free, the
error path unconditionally frees the region:
error:
...
if (region->vm_file)
fput(region->vm_file);
kmem_cache_free(vm_region_jar, region);
This potentially leaves a dangling pointer in nommu_region_tree and
causes RB-tree corruption.
4) When establishing a new private mapping, do_mmap_private() allocates
physical pages and assigns them to region->vm_start:
base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
...
region->vm_start = (unsigned long) base;
If we later fail at vma_iter_prealloc() and jump to error_just_free,
the region struct is freed, but the backing physical memory isn't freed
via free_page_series().
5) In the error label of do_mmap(), the vm_area_struct allocated is
freed by vm_area_free(vma) but not called after vma_close(), leaving
potential memory leak which should be handled by a custom .close
handler of vm_ops.
This commit fixes those issues by introducing new jump label,
error_vma_iter_prealloc, to correctly handle the error case of
vma_iter_prealloc(), updating ret value (1), and move the region updates
after the place that the allocation is finished (2).
Additionally, the commit removes the existing goto label, error, and
consolidates to error_just_free as existing `goto error;` code blocks
always release nommu_region_sem.
Moreover, it only frees region allocated in this request to avoid
freeing the shared, existing region shared by other processes (3), and
free physical memory when do_mmap_private() allocates (4). It also add
vma_close() before vm_area_free() to fix the potential leak (5).
Those issues are discovered by Sashiko, linked below.
Link: https://lore.kernel.org/20260708083829.576036-1-thehajime@gmail.com
Link: https://sashiko.dev/#/patchset/20260702012830.667205-1-thehajime%40gmail.com
Link: https://sashiko.dev/#/patchset/c8513ee5aa8444ec9bf6c276043c9f833016a2fa.1783304131.git.thehajime%40gmail.com
Link: https://sashiko.dev/#/patchset/20260707235137.498738-1-thehajime%40gmail.com
Fixes: b5df092264 ("mm: set up vma iterator for vma_iter_prealloc() calls")
Signed-off-by: Hajime Tazaki <thehajime@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jann Horn <jannh@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Coverage for UFFDIO_REGISTER_MODE_RWP and UFFDIO_RWPROTECT:
rwp-async async mode — touch pages, verify permissions are
auto-restored without a message
rwp-sync sync mode — access blocks, handler resolves via
UFFDIO_RWPROTECT
rwp-pagemap PAGEMAP_SCAN reports still-cold pages via
inverted PAGE_IS_ACCESSED
rwp-mprotect RWP survives mprotect(PROT_NONE) ->
mprotect(PROT_READ|PROT_WRITE) round-trip
rwp-gup GUP walks through a protnone RWP PTE (pipe
write/read drives the GUP path)
rwp-async-toggle UFFDIO_SET_MODE flips between sync and async
without re-registering
rwp-close closing the uffd restores page permissions
rwp-fork RWP survives fork() with EVENT_FORK; child's
PTEs keep the uffd bit
rwp-fork-pin RWP survives fork() on an RO-longterm-pinned
anon page (forces copy_present_page()); child
read auto-resolves and clears the bit, proving
PAGE_NONE was in place
rwp-wp-exclusive register with MODE_WP|MODE_RWP returns -EINVAL
All tests run against anon, shmem, shmem-private, hugetlb, and
hugetlb-private memory, except rwp-fork-pin which is anon-only —
copy_present_page() is the private-anon pinned-exclusive fork path.
Snapshot the RWP additions into tools/include/uapi/linux/userfaultfd.h so
the selftest builds without requiring "make headers" first, matching the
mechanism established by commit 580ea358af ("selftests/mm: fix
additional build errors for selftests").
Link: https://lore.kernel.org/ak-Z9KO2mP9HMOPW@thinkstation
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add an ioctl to toggle async mode at runtime without re-registering the
userfaultfd. This allows a VMM to switch between sync and async RWP modes
on-the-fly -- for example, starting in async mode for working set
scanning, then switching to sync mode to intercept faults during page
eviction.
UFFDIO_SET_MODE takes an enable/disable bitmask of UFFD_FEATURE_* flags.
Only UFFD_FEATURE_RWP_ASYNC is toggleable today; the ioctl rejects any
other bit with -EINVAL. Enabling RWP_ASYNC also requires RWP to have been
negotiated at UFFDIO_API time, mirroring the UFFDIO_API invariant.
Fault-path readers of ctx->features run under mmap_read_lock or a per-VMA
lock; the RMW takes mmap_write_lock and calls vma_start_write() on every
UFFD-armed VMA, so those readers are fully excluded.
userfaultfd_show_fdinfo(), however, reads ctx->features without any lock,
so the RMW is written as a single WRITE_ONCE and fdinfo reads it with
READ_ONCE. That keeps the lockless observer from seeing a mid-RMW
intermediate and removes the audit burden when new toggleable bits are
added later.
When switching to async, pending sync waiters are woken so they retry and
auto-resolve under the new mode.
Link: https://lore.kernel.org/20260708111417.173443-14-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Sync RWP delivers a message and blocks the faulting thread until the
handler resolves the fault. For working-set tracking the VMM does not
need the message: it just needs to know, at scan time, which pages were
touched. Async RWP serves that use case — the kernel restores access
in-place and the faulting thread continues without blocking.
The VMM reconstructs the access pattern after the fact via PAGEMAP_SCAN:
pages whose uffd bit is still set (inverted PAGE_IS_ACCESSED) were not
re-accessed since the last RWP cycle.
Worth calling out: async resolution upgrades writable private anon PTEs
via pte_mkwrite() when can_change_pte_writable() allows, mirroring
do_numa_page(). Without it, every re-access of an RWP'd writable page
would COW-fault a second time.
UFFD_FEATURE_RWP_ASYNC requires UFFD_FEATURE_RWP.
Link: https://lore.kernel.org/20260708111417.173443-13-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
PAGEMAP_SCAN already reports PAGE_IS_WRITTEN from the inverted uffd PTE
bit, targeting the UFFDIO_WRITEPROTECT workflow. UFFDIO_RWPROTECT reuses
the same PTE bit as a marker for read-write protection, but "has been
written" and "has been accessed" are distinct semantic signals — they
happen to share one PTE bit today only because the two implementations
share infrastructure.
Give RWP its own pagemap category so the UAPI does not conflate them:
PAGE_IS_WRITTEN reported on VM_UFFD_WP VMAs, !pte_uffd(pte)
PAGE_IS_ACCESSED reported on VM_UFFD_RWP VMAs, !pte_uffd(pte)
Both still read the same PTE bit today, but each is scoped to the VMA
whose registered mode makes the bit meaningful. If a future
implementation moves RWP to a separate PTE bit, only PAGE_IS_ACCESSED
switches over.
This is a UAPI narrowing. Outside VM_UFFD_WP VMAs the uffd bit is always
clear, so PAGEMAP_SCAN used to flag PAGE_IS_WRITTEN on every present PTE
there — a meaningless duplicate of PAGE_IS_PRESENT. Now PAGE_IS_WRITTEN
fires only inside VM_UFFD_WP VMAs.
pagemap_hugetlb_category() now takes the vma like its PTE/PMD peers.
Link: https://lore.kernel.org/20260708111417.173443-12-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Wire the fault side of read-write protection tracking and turn the
userspace interface on.
An RWP-protected PTE is PAGE_NONE with the uffd bit set. The PROT_NONE
triggers a fault on any access; the uffd bit distinguishes it from plain
mprotect(PROT_NONE) or NUMA hinting.
Fault dispatch, per level:
PTE handle_pte_fault() -> do_uffd_rwp()
PMD __handle_mm_fault() -> do_huge_pmd_uffd_rwp()
hugetlb hugetlb_fault() -> hugetlb_handle_userfault()
The RWP branches gate on userfaultfd_pte_rwp() /
userfaultfd_huge_pmd_rwp() (VM_UFFD_RWP plus the uffd bit) and fall
through to do_numa_page() / do_huge_pmd_numa_page() otherwise. Each
delivers a UFFD_PAGEFAULT_FLAG_RWP message through handle_userfault(); the
handler resolves it with UFFDIO_RWPROTECT clearing MODE_RWP.
userfaultfd_must_wait() and userfaultfd_huge_must_wait() add matching
protnone+uffd waiters so sync-mode fault handlers block correctly.
Expose the UAPI:
UFFDIO_REGISTER_MODE_RWP -> UFFD_API_REGISTER_MODES
UFFD_FEATURE_RWP -> UFFD_API_FEATURES
_UFFDIO_RWPROTECT -> UFFD_API_RANGE_IOCTLS
UFFD_API_RANGE_IOCTLS_BASIC
UFFD_FEATURE_RWP is masked out at UFFDIO_API time when PROT_NONE is not
available or VM_UFFD_RWP aliases VM_NONE (32-bit), so userspace never sees
an advertised-but-broken feature.
Works on anonymous, shmem, and hugetlb memory.
Link: https://lore.kernel.org/20260708111417.173443-11-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add the userspace interface for read-write protection tracking:
- UFFDIO_REGISTER_MODE_RWP register a range for RWP tracking
- UFFD_FEATURE_RWP capability bit
- UFFDIO_RWPROTECT install / remove RWP on a range
Introduce CONFIG_USERFAULTFD_RWP, auto-selected on 64-bit kernels with
ARCH_HAS_PTE_PROTNONE and HAVE_ARCH_USERFAULTFD_WP. The symbol gates
VM_UFFD_RWP (previously aliased to VM_NONE) and the smaps/trace-flag hooks
added in the preparatory patches; without it the UAPI bits added here have
nothing to drive and would be unreachable.
Registration sets VM_UFFD_RWP on the VMA. Combining MODE_WP with MODE_RWP
is rejected because both modes claim the uffd PTE bit.
UFFDIO_RWPROTECT is the bidirectional counterpart of
UFFDIO_WRITEPROTECT:
- MODE_RWP change_protection() with MM_CP_UFFD_RWP
installs PAGE_NONE and sets the uffd bit on
present PTEs
- !MODE_RWP change_protection() with MM_CP_UFFD_RWP_RESOLVE
restores vma->vm_page_prot and clears the bit
userfaultfd_clear_vma() runs the same resolve pass on unregister so RWP
state cannot outlive the uffd.
Re-registering a range must not drop a mode that installs per-PTE markers
(WP or RWP); doing so returns -EBUSY. This also closes a pre-existing
window where re-registering without MODE_WP would strand uffd-wp markers:
before, those caused extra write-faults but were otherwise benign; with
RWP preservation in place, a subsequent mprotect() on a VM_UFFD_RWP VMA
would silently promote the stale markers to RWP.
The feature is not yet advertised. UFFDIO_REGISTER_MODE_RWP,
UFFD_FEATURE_RWP, and _UFFDIO_RWPROTECT are intentionally absent from
UFFD_API_REGISTER_MODES, UFFD_API_FEATURES, and UFFD_API_RANGE_IOCTLS, so
UFFDIO_API masks them out and the register-mode validator rejects the bit.
The follow-up patch adds fault dispatch and exposes the UAPI.
Link: https://lore.kernel.org/20260708111417.173443-10-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Three mm paths outside the fault handler gate on the uffd PTE bit today:
khugepaged (skip collapse on ranges carrying markers), rmap (cap unmap
batching), and GUP (force a fault through gup_can_follow_protnone).
Extend each to treat VM_UFFD_RWP the same as VM_UFFD_WP; otherwise per-PTE
RWP state is silently destroyed or bypassed.
khugepaged: try_collapse_pte_mapped_thp() and
file_backed_vma_is_retractable() already refuse to collapse or retract
page tables on ranges carrying the uffd PTE bit. Broaden the VMA
predicate from userfaultfd_wp() to userfaultfd_protected() so VM_UFFD_RWP
ranges get the same protection. hpage_collapse_scan_pmd() needs no change
— its existing pte_uffd() check already catches an RWP PTE because it
carries the uffd bit.
rmap: folio_unmap_pte_batch() caps batching at 1 for VM_UFFD_RWP so the
restore path handles each PTE with its own marker.
GUP: gup_can_follow_protnone() forces a fault on VM_UFFD_RWP VMAs
regardless of FOLL_HONOR_NUMA_FAULT. RWP uses protnone as an
access-tracking marker, not for NUMA hinting, so any GUP — read or write
— must go through the userfaultfd fault path.
Link: https://lore.kernel.org/20260708111417.173443-9-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The uffd PTE bit must survive any kernel path that rewrites a PTE on a
VM_UFFD_RWP VMA, otherwise the marker that carries PAGE_NONE semantics is
silently dropped and the next access leaks past RWP tracking. Wire the
preservation through every path that rewrites a VM_UFFD_RWP PTE.
Swap and device-exclusive: do_swap_page(), restore_exclusive_pte(), and
unuse_pte() (swapoff()) re-apply PAGE_NONE when the swap PTE carries the
uffd bit and the VMA has VM_UFFD_RWP.
Migration: remove_migration_pte() and remove_migration_pmd() do the same
after the migration entry is replaced with a real PTE/PMD.
Fork: __copy_present_ptes(), copy_present_page(), copy_nonpresent_pte(),
copy_huge_pmd(), copy_huge_non_present_pmd(), and
copy_hugetlb_page_range() keep the uffd bit on the child when the
destination VMA has VM_UFFD_RWP, matching the existing VM_UFFD_WP
handling. Add VM_UFFD_RWP to VM_COPY_ON_FORK so the flag itself
propagates.
mprotect(): change_pte_range() and change_huge_pmd() restore PAGE_NONE
after pte_modify()/pmd_modify() have recomputed the base protection from a
(possibly user-changed) vm_page_prot. pte_modify() preserves _PAGE_UFFD,
so the bit stays; we just have to force PAGE_NONE back on top.
Link: https://lore.kernel.org/20260708111417.173443-8-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Preparatory patch. Add the change_protection() primitive that userfaultfd
RWP will use.
An RWP-protected PTE is PAGE_NONE with the uffd PTE bit set. The
PROT_NONE half makes the CPU fault on any access; the uffd bit
distinguishes an RWP fault from a plain mprotect(PROT_NONE) or NUMA
hinting fault. MM_CP_UFFD_WP and MM_CP_UFFD_RWP share the same PTE bit,
so the two cannot be used together on the same range.
Two new change_protection() flags:
MM_CP_UFFD_RWP install PAGE_NONE and set the uffd bit
MM_CP_UFFD_RWP_RESOLVE restore vma->vm_page_prot, clear the uffd bit
Both are wired through change_pte_range(), change_huge_pmd(), and
hugetlb_change_protection() so anon, shmem, THP, and hugetlb all share the
same semantics.
Link: https://lore.kernel.org/20260708111417.173443-7-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Preparatory patch for userfaultfd read-write protection (RWP). RWP
extends userfaultfd protection from plain write-protection (WP) to full
read-write protection: accesses to an RWP-protected range -- reads as well
as writes -- trap through userfaultfd.
Reserve VM_UFFD_RWP, add the userfaultfd_rwp() and userfaultfd_protected()
helpers, and wire up the smaps "ur" entry and the trace-flag table the
rest of the series will use. The flag is gated on CONFIG_USERFAULTFD_RWP,
which is introduced together with the UAPI in a later patch; until then
VM_UFFD_RWP aliases VM_NONE and every downstream check folds to dead code.
Nothing sets or queries the flag yet.
Link: https://lore.kernel.org/20260708111417.173443-6-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Userfaultfd RWP will reuse the uffd-wp PTE bit to mark access-tracking
PTEs, alongside the write-protected ones it already marks. The bit's
meaning now depends on the VMA flag (WP or RWP), not on its name.
Rename the kernel-internal names that describe the bit:
- pte/pmd/huge_pte accessors (and swap variants)
- pgtable_supports_uffd() capability query
- SCAN_PTE_UFFD khugepaged enum
The ftrace string emitted by mm_khugepaged_scan_pmd for this enum is
kept as "pte_uffd_wp" so existing trace-based tooling keeps matching.
Pure mechanical rename -- no behavior change.
Link: https://lore.kernel.org/20260708111417.173443-4-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The uffd-wp PTE bit is about to gain a second consumer: userfaultfd RWP
will use the same bit to mark access-tracking PTEs, distinct from
mprotect(PROT_NONE) or NUMA-hinting PTEs. WP vs RWP semantics come from
the VMA flag; the bit is just "uffd has claimed this entry." Drop the
"_wp" suffix from the arch-private bit macros so they reflect that.
x86: _PAGE_BIT_UFFD_WP -> _PAGE_BIT_UFFD
_PAGE_UFFD_WP -> _PAGE_UFFD
_PAGE_SWP_UFFD_WP -> _PAGE_SWP_UFFD
arm64: PTE_UFFD_WP -> PTE_UFFD
PTE_SWP_UFFD_WP -> PTE_SWP_UFFD
riscv: _PAGE_UFFD_WP -> _PAGE_UFFD
_PAGE_SWP_UFFD_WP -> _PAGE_SWP_UFFD
Pure mechanical rename -- no behavior change.
Link: https://lore.kernel.org/20260708111417.173443-3-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "userfaultfd: working set tracking for VM guest memory", v10.
This series adds userfaultfd support for tracking the working set of VM
guest memory, so a VMM can identify hot pages and reclaim cold ones to
tiered or remote storage.
This patch (of 15):
pte_protnone() and pmd_protnone() detect present-but-inaccessible page
table entries. This capability is useful beyond NUMA balancing -- for
example, userfaultfd working set tracking uses protnone PTEs to track page
access without unmapping pages.
Introduce CONFIG_ARCH_HAS_PTE_PROTNONE to decouple the protnone PTE
infrastructure from CONFIG_NUMA_BALANCING. The six architectures that
support protnone PTEs (x86_64, arm64, powerpc, s390, riscv, loongarch) now
select this option, and CONFIG_NUMA_BALANCING depends on it.
No functional change -- the same set of architectures continues to have
working protnone support, but the infrastructure is now available
independently of NUMA balancing.
Link: https://lore.kernel.org/20260708111417.173443-1-kirill@shutemov.name
Link: https://lore.kernel.org/20260708111417.173443-2-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Assisted-by: Claude:claude-opus-4-6
Acked-by: SeongJae Park <sj@kernel.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: James Houghton <jthoughton@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm: clean up folio LRU and swap declarations", v9.
This series splits folio LRU and swap cleanup into three steps:
- move the page-cluster sysctl next to swap readahead in
mm/swap_state.c
- rename mm/swap.c to mm/folio.c after the swap-specific code
moves out
- move MM-internal reclaim declarations out of include/linux/swap.h
After this series, swap cache and swap-in readahead stay in
mm/swap_state.c. Folio LRU helpers live in mm/folio.c, and MM-internal
reclaim/workingset declarations move from include/linux/swap.h to
mm/internal.h (public LRU helpers used outside mm/ remain in swap.h).
The first patch handles the swap-specific page-cluster state before the
file rename, so the rename commit only carries folio LRU code. The last
patch keeps the LRU helpers used outside mm/ in include/linux/swap.h and
moves the internal reclaim/workingset declarations to mm/internal.h.
This patch (of 3):
page_cluster and the vm.page-cluster sysctl are only used by swap-in
readahead in swap_state.c. Move them out of swap.c together with
swap_readahead_setup(), and make page_cluster static to that file.
Rename swap_setup() while moving it as well. The helper is internal to MM
and now only sets up swap readahead defaults and its sysctl hook, so the
more specific name matches its reduced scope.
Call swap_readahead_setup() from swap_init() after moving it, keeping the
readahead defaults and sysctl registration with swap_state.c
initialization.
swap_setup() previously lived in mm/swap.c, which is built
unconditionally, so the vm.page-cluster sysctl was registered also on
CONFIG_SWAP=n kernels. After moving the setup into swap_state.c, which is
built only when CONFIG_SWAP is enabled, vm.page-cluster is no longer
registered there. The knob only tunes swap-in readahead and had no effect
without swap.
Link: https://lore.kernel.org/20260708-ch-swap-series-plus-folio-lru-cleanup-v9-0-2bc72b4f8730@gmail.com
Link: https://lore.kernel.org/20260708-ch-swap-series-plus-folio-lru-cleanup-v9-1-2bc72b4f8730@gmail.com
Signed-off-by: Jianyue Wu <wujianyue000@gmail.com>
Suggested-by: Baoquan He <bhe@redhat.com>
Suggested-by: Barry Song <baohua@kernel.org>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Kairui Song <kasong@tencent.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We are doing a lot of redundant lru_add_drain() calls in do_swap_page(),
especially for synchronous I/O devices. For example, the test program
below currently ends up draining lru_cache 100% of the time:
int main(int argc, char *argv[])
{
int i;
#define SIZE 100*1024*1024
while(1) {
volatile int *p = mmap(0, SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
for (int i = 0; i < SIZE/sizeof(int); i++)
p[i] = i%64;
madvise((void *)p, SIZE, MADV_PAGEOUT);
for (int i = 0; i < SIZE/sizeof(int); i++)
p[i] = i%64;
munmap(p, SIZE);
}
return 0;
}
Folio reuse now relies primarily on the exclusive hint, making lru_cache
draining to drop the refcount in lru_cache largely irrelevant. For a
kernel build with a minimal configuration running in a 1 GB memcg, this
patch skips more than 43,000 redundant local LRU drains.
Link: https://lore.kernel.org/20260701235955.36126-4-baohua@kernel.org
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm: drop redundant lru_add_drain in anon folio reuse paths",
v3.
We are doing a large number of redundant lru_add_drain() calls in both
wp_can_reuse_anon_folio() and do_swap_page(), leading to LRU lock
contention and unnecessary overhead.
In wp_can_reuse_anon_folio(), we can check the refcount against the
lru_cache before deciding to drain. In do_swap_page(), the drain is now
entirely redundant after Kairui's work to route SYNC I/O through the
swapcache in the same way as ASYNC I/O.
Build the kernel within a 1 GB memcg using 20 threads with zRAM swap. The
number of lru_add_drain() calls is reduced from 276,278 to 226,318, a
reduction of about 18%.
Build the kernel within an 800 MB memcg using 20 threads with zRAM swap.
The number of lru_add_drain() calls is reduced from 778,950 to 541,149, a
reduction of 30.5%.
This patch (of 4):
There is a case where `folio_ref_count(folio) == 3` and
`!folio_test_swapcache(folio)`. In that case, both
`folio_ref_count(folio) > 3` and
`folio_ref_count(folio) > 1 + folio_test_swapcache(folio)` evaluate
false, causing an unnecessary local LRU drain.
During an Ubuntu boot, I observed over 5,000 redundant local LRU drains.
For a kernel build with a minimal configuration, I observed more than
20,000 redundant drains.
Fix this by checking against: `1 + in_swapcache + in_lrucache` instead of
hardcoding `folio_ref_count(folio) > 3`.
[baohua@kernel.org: rename in_lru_cache to maybe_in_lru_cache]
Link: https://lore.kernel.org/20260708145718.82690-1-baohua@kernel.org
Link: https://lore.kernel.org/20260701235955.36126-1-baohua@kernel.org
Link: https://lore.kernel.org/20260701235955.36126-2-baohua@kernel.org
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Kairui Song <kasong@tencent.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Baoquan He <baoquan.he@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "Keep tail page private zero at free and folio split", v3.
This patchset makes sure tail_page->private is zero before compound or
high-order pages are returned to the allocator. It also checks tail pages
that become new folio heads during large folio split, before their private
fields are used by new folios.
Note on ZONE_DEVICE and DAX page/folio
===
ZONE_DEVICE and DAX use prep_compound_tail() to reinitialize folios, so
tail_page->private was reset before this patchset. There was a concern
that after this patchset stale ->private can appear after ZONE_DEVICE/DAX
folio initialization. My reasoning is that no code sets ZONE_DEVICE/DAX
page->private, so their page->private stays zero all the time.
ZONE_DEVICE_PRIVATE page migration only supports anonymous memory without
swapcache, so after the migration ->private remains zero.
But let me know if my reasoning is wrong. It can be fixed by adding
->private zeroing code in ZONE_DEVICE/DAX folio initialization code.
Motivation
===
page->private is zeroed at page free time since commit ac1ea21959
("mm/page_alloc: clear page->private in free_pages_prepare()"), since we
concluded that it might be too much to ask every page user to free a page
with ->private zeroed. The holder of the last page reference might not
know whether ->private needs to be cleared.
For compound and high-order pages, tail_page->private can also leak to
later users if it is left uncleared. The page allocation path does not
zero every tail_page->private field, so they can be seen by new users and
cause unexpected issues[1].
Check tail_page->private at page free time, and check tail pages that
become new folio heads during large folio split. With those checks in
place, prep_compound_tail() no longer needs to clear tail_page->private
when preparing compound page metadata.
Overview
===
1. Patch 1 clears all pages ->private before percpu-km frees them.
2. Patch 2 removes setting page->private in compaction code when a free
page is taken out of the buddy allocator. cc->freepages is indexed by
page order, so storing the free page order in page->private is
redundant. In alloc_contig_frozen_range_noprof(),
isolate_freepages_range() is used to grab free pages from buddy
allocator and it leaves the aforementioned page->private set until
either split_free_frozen_pages() or prep_new_page() is called. That
stale value without resetting triggers the tail_page->private nonzero
check once set_page_private(0) is removed from prep_compound_tail().
3. Patch 3 adds back the page->private check for tail pages promoted to new
folio heads in __split_folio_to_order().
4. Patch 4 adds a tail_page->private check in the page free path.
5. Patch 5 removes tail_page->private zeroing from prep_compound_tail().
This patch (of 5):
page->private is cleared in free page path. In a subsequent commit,
tail_page->private will be checked and ensured to be zero. Clearing
percpu-km allocated pages' ->private to prevent triggering warnings later,
namely undo what we did in pcpu_create_chunk().
Link: https://lore.kernel.org/20260709-keep-subpage-private-zero-at-free-v3-0-7e4fe155f5b9@nvidia.com
Link: https://lore.kernel.org/20260709-keep-subpage-private-zero-at-free-v3-1-7e4fe155f5b9@nvidia.com
Link: https://lore.kernel.org/all/20260206174017.128673-1-mikhail.v.gavrilov@gmail.com/ [1]
Signed-off-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_call() failure was causing the context to be stopped, but
asynchronously by the kdamond thread. To handle the race, the caller had
to stop the context. damon_call() is updated to do the stop on its own.
Remove the damon_stop() call from the damon_call() error handling.
Link: https://lore.kernel.org/20260706140628.87414-12-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_call() failure was causing the context to be stopped, but
asynchronously by the kdamond thread. To handle the race, the caller had
to stop the context. damon_call() is updated to do the stop on its own.
Remove the damon_stop() call from the damon_call() error handling.
Link: https://lore.kernel.org/20260706140628.87414-11-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_call() failure means the DAMON context started its termination. The
termination is asynchronously done in kdamond thread. The caller's error
handling should handle the race, too. It is complicated and easy to make
mistakes.
Update damon_call() to ensure the context is stopped in the case, by
waiting until the completion is confirmed.
Link: https://lore.kernel.org/20260706140628.87414-10-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_stop() was theoretically able to return failure while keeping the
second context for mtier running. mtier stops its contexts one by one
with two damon_stop() call for the reason. damon_stop() is refactored to
always successfully stop all requested DAMON contexts. The two calls are
unnecessary. Use only single damon_stop() call for all contexts.
Link: https://lore.kernel.org/20260706140628.87414-9-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
damon_stop() has no reason to fail. It returns an error code only for
possible future changes that can make it fail. Such a change has not been
made yet, and this only makes the error handling complicated and
confusing. Ensure it returns no error.
Link: https://lore.kernel.org/20260706140628.87414-4-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/damon: refactor damon_{start,stop,commit}() for simple
error handling".
damon_start() and damon_stop() could leave a few of requested DAMON
contexts running when they return an error. damon_commit() failure stops
the DAMON context, but in an asynchronous way. Callers should stop the
left-over DAMON contexts. It is easy to make mistakes, and indeed a few
bugs from such mistakes were found and fixed.
Refactor the core API functions to guarantee contexts are completely
stopped under failures. Remove the caller side error handlers that are no
longer needed due to the refactoring.
Patches Sequence
================
Patch 1 refactors damon_start() to ensure all contexts are stopped for
failures. Patch 2 updates unnecessary damon_start() error handling from
mtier sample module.
Patch 3 refactors damon_stop() to always success. Patches 4-6 updates
callers (damon_{sysfs,reclaim lru_sort}) to ignore the return value.
Patch 7 update damon_stop() return value to void. Patch 8 simplifies
damon_stop() error handling in mtier sample module.
Patch 9 refactors damon_call() to return errors only after the context
is completely stopped. Patches 10 and 11 remove unnecessary error
handlings from callers (wsse and prcl sample modules).
This patch (of 11):
When multiple contexts are passed to damon_start(), the function starts
the contexts one by one. If any of the operations fails, it immediately
returns an error. Contexts that successfully started before the failure
keep running. The caller should catch this and stop the contexts. It is
complicated and easy to make mistakes. Stop all contexts in damon_start()
under the failures.
Link: https://lore.kernel.org/20260706140628.87414-1-sj@kernel.org
Link: https://lore.kernel.org/20260706140628.87414-2-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
In the ensure_file() function, the "not_exist" code path checks whether
$dir exists as a regular file. However, the intent is to verify that the
target file ($file) does not exist, not the $dir. Testing $dir makes the
existence check effectively useless -- it tests the wrong path and thus
never catches the case where the file is unexpectedly present.
Replace $dir with $file so the not_exist verification targets the correct
path.
Link: https://lore.kernel.org/20260706134305.5224-1-a929244872@163.com
Signed-off-by: wang wei <a929244872@163.com>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
While the GCC and Clang compilers already define __ASSEMBLER__
automatically when compiling assembly code, __ASSEMBLY__ is a macro that
only gets defined by the Makefiles in the kernel. This can be very
confusing when switching between userspace and kernelspace coding, or when
dealing with uapi headers that rather should use __ASSEMBLER__ instead.
So let's standardize now on the __ASSEMBLER__ macro that is provided by
the compilers.
This is a completely mechanical patch (done with a simple "sed -i"
statement.
Link: https://lore.kernel.org/20260619154704.41293-1-thuth@redhat.com
Signed-off-by: Thomas Huth <thuth@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add a sysctl panic_on_unrecoverable_memory_failure (disabled by default)
that triggers a kernel panic when memory_failure() encounters pages that
cannot be recovered. This provides a clean crash with useful debug
information rather than allowing silent data corruption or a delayed crash
at an unrelated code path.
Panic eligibility is intentionally narrow: only MF_MSG_KERNEL with result
== MF_IGNORED panics. After the previous patch, MF_MSG_KERNEL covers
PG_reserved pages and the kernel-owned pages promoted from
get_hwpoison_page() via -ENOTRECOVERABLE (slab, page tables,
large-kmalloc).
All other action types are excluded:
- MF_MSG_GET_HWPOISON and MF_MSG_KERNEL_HIGH_ORDER can be reached by
transient refcount races with the page allocator (an in-flight buddy
allocation has refcount 0 and is no longer on the buddy free list,
briefly), and panicking on them would risk killing the box for what
is actually a recoverable userspace page.
- MF_MSG_UNKNOWN means identify_page_state() could not classify the
page; that is precisely the wrong basis for a panic decision.
Link: https://lore.kernel.org/20260630-ecc_panic-v10-4-c6ed5b62eea2@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The previous patch teaches get_any_page() to return -ENOTRECOVERABLE for
stable unhandlable kernel pages (PG_reserved, slab, page tables,
large-kmalloc). memory_failure() still folds every negative return into
MF_MSG_GET_HWPOISON, so callers that want to react to the unrecoverable
cases (a panic option, smarter logging) cannot tell them apart from
transient page-allocator races.
Turn the post-call branch into a switch over the get_hwpoison_page()
return code: map -ENOTRECOVERABLE to MF_MSG_KERNEL and any other negative
return to MF_MSG_GET_HWPOISON. case 0 keeps the existing free-buddy /
kernel-high-order handling and case 1 falls through to the rest of
memory_failure() unchanged.
The MF_MSG_KERNEL label and tracepoint string are kept as "reserved kernel
page" to avoid breaking userspace tools that match on those literals; the
enum value still adequately tags the failure even though it now also
covers slab, page tables and large-kmalloc pages.
Link: https://lore.kernel.org/20260630-ecc_panic-v10-3-c6ed5b62eea2@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Suggested-by: David Hildenbrand <david@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
get_any_page() collapses every HWPoisonHandlable() rejection into a
single -EIO via the __get_hwpoison_page() -> -EBUSY -> shake_page()
-> retry path. That is correct for the transient case (a userspace
folio briefly off LRU during migration or compaction, which a later
shake can drag back), but wrong for stable kernel-owned pages: slab,
page-table, large-kmalloc and PG_reserved pages will never become
HWPoisonHandlable(), so the retry loop is wasted work and the final
-EIO loses the "this is structurally unrecoverable" information.
memory_failure() then maps -EIO into MF_MSG_GET_HWPOISON, which the
panic-on-unrecoverable sysctl deliberately does not act on.
Introduce is_kernel_owned_page(), a small predicate that positively
identifies pages the hwpoison handler cannot recover from:
is_kernel_owned_page(p) :=
PageReserved(p) ||
PageSlab(head) || PageTable(head) || PageLargeKmalloc(head)
where head = compound_head(p).
PG_reserved is a per-page flag (PF_NO_COMPOUND) and is tested on the
page directly. The slab, page-table and large-kmalloc page-type bits
are only stored on the head page, so those tests resolve the compound
head first, then re-read compound_head(page) afterwards: a concurrent
split or compound free that moves head invalidates the just-read flags
and the loop retries. The lookup still takes no refcount, mirroring
the rest of get_any_page(); the recheck closes the common split race,
and a residual free->alloc->free in the same window can only mis-tag
a genuinely poisoned page, never reclassify a handlable one.
No MF_SOFT_OFFLINE / page_has_movable_ops() opt-out is needed: a
movable_ops page is always PageOffline or PageZsmalloc, whose page_type is
mutually exclusive with slab, page-table and large-kmalloc, and it never
carries PG_reserved, so it can never match any of the checks above.
The list is intentionally not exhaustive. vmalloc and kernel-stack pages,
for example, do not carry a page_type bit and would need a different
oracle; they keep going through the existing retry path unchanged. This
is the smallest set we can identify with certainty by page type.
Wire the helper into the top of get_any_page() to short-circuit those
pages before the retry loop runs. On a hit, drop the caller's
MF_COUNT_INCREASED reference (if any) and return -ENOTRECOVERABLE straight
away. Pages outside the helper's positive list still take the existing
retry path and return -EIO, leaving operator-visible behaviour for those
cases unchanged.
Extend the unhandlable-page pr_err() to fire for either errno and update
the get_hwpoison_page() kerneldoc to document the new return.
memory_failure() still folds every negative return into
MF_MSG_GET_HWPOISON via its existing "else if (res < 0)" branch, so this
patch on its own only changes the errno that soft_offline_page() can
propagate to its callers. A follow-up wires -ENOTRECOVERABLE through
memory_failure() and reports MF_MSG_KERNEL for the unrecoverable cases,
which is what the panic_on_unrecoverable_memory_failure sysctl observes.
Link: https://lore.kernel.org/20260630-ecc_panic-v10-2-c6ed5b62eea2@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Suggested-by: David Hildenbrand <david@kernel.org>
Suggested-by: Lance Yang <lance.yang@linux.dev>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm/memory-failure: add panic option for unrecoverable
pages", v10.
A multi-bit ECC error on a kernel-owned page that the memory failure
handler cannot recover is currently swallowed: PG_hwpoison is set, the
event is logged, and the kernel keeps running. The corrupted memory
remains accessible to the kernel and either drives silent data corruption
or surfaces seconds-to-minutes later as an apparently unrelated crash. In
a large fleet that delayed, unattributable crash turns into significant
engineering effort to root-cause; in a kdump configuration, by the time
the crash happens the original error context (faulting PFN, MCE/GHES
record, page state) is long gone.
This series adds an opt-in sysctl,
vm.panic_on_unrecoverable_memory_failure, that converts an unrecoverable
kernel-page hwpoison event into an immediate panic with a clean
dmesg/vmcore that still contains the original failure context. The
default is disabled so existing workloads see no change.
There is a selftest that test different cases, and I tested it using
the following variants:
┌─────────┬──────────┬───────────────────────────────────────────────────────────┐
│ Variant │ PFN │ Result │
├─────────┼──────────┼───────────────────────────────────────────────────────────┤
│ rodata │ 0x2600 │ Panic with "Memory failure: 0x2600: unrecoverable page" │
├─────────┼──────────┼───────────────────────────────────────────────────────────┤
│ slab │ 0x100032 │ Panic with "Memory failure: 0x100032: unrecoverable page" │
├─────────┼──────────┼───────────────────────────────────────────────────────────┤
│ pgtable │ 0x100000 │ Panic with "Memory failure: 0x100000: unrecoverable page" │
└─────────┴──────────┴───────────────────────────────────────────────────────────┘
Each one shows the same call trace, exactly the path the series builds:
hard_offline_page_store
→ memory_failure
→ action_result
→ panic("Memory failure: %#lx: unrecoverable page")
This patch (of 5):
The first entry of error_states[],
{ reserved, reserved, MF_MSG_KERNEL, me_kernel },
is unreachable. identify_page_state() has two callers, and neither
one can dispatch a PG_reserved page to me_kernel():
* memory_failure() reaches identify_page_state() only after
get_hwpoison_page() returned 1. get_any_page() reaches that
return only via __get_hwpoison_page(), which only takes a
refcount when the page is HWPoisonHandlable().
HWPoisonHandlable() is an allowlist for LRU, free-buddy, and
(for soft-offline) movable_ops pages -- PG_reserved pages do
not satisfy any of these, so they fail with -EBUSY/-EIO long
before identify_page_state() runs.
* try_memory_failure_hugetlb() reaches identify_page_state() only
via the MF_HUGETLB_IN_USED branch, where the page is necessarily
a hugetlb folio. hugetlb folios don't carry PG_reserved at that
point: hugetlb_folio_init_vmemmap() calls __folio_clear_reserved()
during init, so the reserved entry would not match even if it
were still present.
me_kernel() never executes and the entry exists only to be matched
against by code that cannot see it.
Drop the entry, the me_kernel() helper, and the now-unused
"reserved" macro. Leave the MF_MSG_KERNEL enum value in place: it
remains part of the tracepoint and pr_err() string tables, and
follow-on work to classify unrecoverable kernel pages can reuse it
without churning the user-visible enum.
No functional change.
Link: https://lore.kernel.org/20260630-ecc_panic-v10-0-c6ed5b62eea2@debian.org
Link: https://lore.kernel.org/20260630-ecc_panic-v10-1-c6ed5b62eea2@debian.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Suggested-by: David Hildenbrand <david@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
