linux.git/mm, branch v6.14-rc6

Merge tag 'mm-hotfixes-stable-2025-03-08-16-27' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2025-03-09T00:34:06+00:00

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()
  ...

Merge tag 'slab-for-6.14-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab

2025-03-07T22:22:41+00:00

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

fs/pipe: add simpler helpers for common cases

2025-03-07T04:25:35+00:00

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

mm/page_alloc: fix uninitialized variable

2025-03-06T05:36:20+00:00

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 
Reviewed-by: Vlastimil Babka 
Cc: Michal Hocko 
Cc: Mel Gorman 
Cc: 
Signed-off-by: Andrew Morton

Revert "mm/page_alloc.c: don't show protection in zone's ->lowmem_reserve[] for empty zone"

2025-03-06T05:36:19+00:00

Commit 96a5c186efff ("mm/page_alloc.c: don't show protection in zone's
->lowmem_reserve[] for empty zone") removes the protection of lower zones
from allocations targeting memory-less high zones.  This had an unintended
impact on the pattern of reclaims because it makes the high-zone-targeted
allocation more likely to succeed in lower zones, which adds pressure to
said zones.  I.e, the following corresponding checks in
zone_watermark_ok/zone_watermark_fast are less likely to trigger:

        if (free_pages <= min + z->lowmem_reserve[highest_zoneidx])
                return false;

As a result, we are observing an increase in reclaim and kswapd scans, due
to the increased pressure.  This was initially observed as increased
latency in filesystem operations when benchmarking with fio on a machine
with some memory-less zones, but it has since been associated with
increased contention in locks related to memory reclaim.  By reverting
this patch, the original performance was recovered on that machine.

The original commit was introduced as a clarification of the
/proc/zoneinfo output, so it doesn't seem there are usecases depending on
it, making the revert a simple solution.

For reference, I collected vmstat with and without this patch on a freshly
booted system running intensive randread io from an nvme for 5 minutes.  I
got:

rpm-6.12.0-slfo.1.2 ->  pgscan_kswapd 5629543865
Patched             ->  pgscan_kswapd 33580844

33M scans is similar to what we had in kernels predating this patch. 
These numbers is fairly representative of the workload on this machine, as
measured in several runs.  So we are talking about a 2-order of magnitude
increase.

Link: https://lkml.kernel.org/r/20250226032258.234099-1-krisman@suse.de
Fixes: 96a5c186efff ("mm/page_alloc.c: don't show protection in zone's ->lowmem_reserve[] for empty zone")
Signed-off-by: Gabriel Krisman Bertazi 
Reviewed-by: Vlastimil Babka 
Acked-by: Michal Hocko 
Acked-by: Mel Gorman 
Cc: Baoquan He 
Cc: 
Signed-off-by: Andrew Morton

mm: fix finish_fault() handling for large folios

2025-03-06T05:36:18+00:00

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: 43e027e41423 ("mm: memory: extend finish_fault() to support large folio")
Signed-off-by: Brian Geffon 
Suggested-by: Baolin Wang 
Reported-by: Marek Maslanka 
Cc: Hugh Dickins 
Cc: David Hildenbrand 
Cc: Hugh Dickens 
Cc: Kefeng Wang 
Cc: Matthew Wilcow (Oracle) 
Cc: Suren Baghdasaryan 
Cc: Zi Yan 
Cc: 
Signed-off-by: Andrew Morton

mm: don't skip arch_sync_kernel_mappings() in error paths

2025-03-06T05:36:18+00:00

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: 2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified")
Fixes: 0c95cba49255 ("mm: apply_to_pte_range warn and fail if a large pte is encountered")
Signed-off-by: Ryan Roberts 
Reviewed-by: Anshuman Khandual 
Reviewed-by: Catalin Marinas 
Cc: Christop Hellwig 
Cc: "Uladzislau Rezki (Sony)" 
Cc: 
Signed-off-by: Andrew Morton

mm: shmem: remove unnecessary warning in shmem_writepage()

2025-03-06T05:36:18+00:00

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: 9a976f0c847b ("shmem: skip page split if we're not reclaiming")
Signed-off-by: Ricardo Cañuelo Navarro 
Reported-by: Pengfei Xu 
Closes: https://lore.kernel.org/lkml/ZZ9PShXjKJkVelNm@xpf.sh.intel.com/ [1]
Suggested-by: Hugh Dickins 
Reviewed-by: Baolin Wang 
Cc: Florent Revest 
Cc: Christian Brauner 
Cc: David Hildenbrand 
Cc: Davidlohr Bueso 
Cc: Florent Revest 
Cc: Luis Chamberalin 
Signed-off-by: Andrew Morton

userfaultfd: fix PTE unmapping stack-allocated PTE copies

2025-03-06T05:36:18+00:00

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: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Suren Baghdasaryan 
Reported-by: Peter Xu 
Reviewed-by: Peter Xu 
Cc: Andrea Arcangeli 
Cc: Barry Song <21cnbao@gmail.com>
Cc: Barry Song 
Cc: David Hildenbrand 
Cc: Hugh Dickins 
Cc: Jann Horn 
Cc: Kalesh Singh 
Cc: Liam R. Howlett 
Cc: Lokesh Gidra 
Cc: Lorenzo Stoakes 
Cc: Matthew Wilcow (Oracle) 
Cc: 
Signed-off-by: Andrew Morton

userfaultfd: do not block on locking a large folio with raised refcount

2025-03-06T05:36:17+00:00

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: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI")
Signed-off-by: Suren Baghdasaryan 
Reported-by: Lokesh Gidra 
Reviewed-by: Peter Xu 
Acked-by: Liam R. Howlett 
Cc: Andrea Arcangeli 
Cc: Barry Song <21cnbao@gmail.com>
Cc: Barry Song 
Cc: David Hildenbrand 
Cc: Hugh Dickins 
Cc: Jann Horn 
Cc: Kalesh Singh 
Cc: Lorenzo Stoakes 
Cc: Matthew Wilcow (Oracle) 
Cc: 
Signed-off-by: Andrew Morton