linux.git/mm/huge_memory.c, branch v5.4.301

mm/huge_memory: fix dereferencing invalid pmd migration entry

2025-06-27T10:02:58+00:00

commit be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7 upstream.

When migrating a THP, concurrent access to the PMD migration entry during
a deferred split scan can lead to an invalid address access, as
illustrated below.  To prevent this invalid access, it is necessary to
check the PMD migration entry and return early.  In this context, there is
no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the
equality of the target folio.  Since the PMD migration entry is locked, it
cannot be served as the target.

Mailing list discussion and explanation from Hugh Dickins: "An anon_vma
lookup points to a location which may contain the folio of interest, but
might instead contain another folio: and weeding out those other folios is
precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of
replacing the wrong folio" comment a few lines above it) is for."

BUG: unable to handle page fault for address: ffffea60001db008
CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60
Call Trace:

try_to_migrate_one+0x28c/0x3730
rmap_walk_anon+0x4f6/0x770
unmap_folio+0x196/0x1f0
split_huge_page_to_list_to_order+0x9f6/0x1560
deferred_split_scan+0xac5/0x12a0
shrinker_debugfs_scan_write+0x376/0x470
full_proxy_write+0x15c/0x220
vfs_write+0x2fc/0xcb0
ksys_write+0x146/0x250
do_syscall_64+0x6a/0x120
entry_SYSCALL_64_after_hwframe+0x76/0x7e

The bug is found by syzkaller on an internal kernel, then confirmed on
upstream.

Link: https://lkml.kernel.org/r/20250421113536.3682201-1-gavinguo@igalia.com
Link: https://lore.kernel.org/all/20250414072737.1698513-1-gavinguo@igalia.com/
Link: https://lore.kernel.org/all/20250418085802.2973519-1-gavinguo@igalia.com/
Fixes: 84c3fc4e9c56 ("mm: thp: check pmd migration entry in common path")
Signed-off-by: Gavin Guo 
Acked-by: David Hildenbrand 
Acked-by: Hugh Dickins 
Acked-by: Zi Yan 
Reviewed-by: Gavin Shan 
Cc: Florent Revest 
Cc: Matthew Wilcox (Oracle) 
Cc: Miaohe Lin 
Cc: 
Signed-off-by: Andrew Morton 
[gavin: backport the migration checking logic to __split_huge_pmd]
Signed-off-by: Gavin Guo 
Signed-off-by: Greg Kroah-Hartman

mm/thp: check and bail out if page in deferred queue already

2023-03-11T15:44:05+00:00

commit 81e506bec9be1eceaf5a2c654e28ba5176ef48d8 upstream.

Kernel build regression with LLVM was reported here:
https://lore.kernel.org/all/Y1GCYXGtEVZbcv%2F5@dev-arch.thelio-3990X/ with
commit f35b5d7d676e ("mm: align larger anonymous mappings on THP
boundaries").  And the commit f35b5d7d676e was reverted.

It turned out the regression is related with madvise(MADV_DONTNEED)
was used by ld.lld. But with none PMD_SIZE aligned parameter len.
trace-bpfcc captured:
531607  531732  ld.lld          do_madvise.part.0 start: 0x7feca9000000, len: 0x7fb000, behavior: 0x4
531607  531793  ld.lld          do_madvise.part.0 start: 0x7fec86a00000, len: 0x7fb000, behavior: 0x4

If the underneath physical page is THP, the madvise(MADV_DONTNEED) can
trigger split_queue_lock contention raised significantly. perf showed
following data:
    14.85%     0.00%  ld.lld           [kernel.kallsyms]           [k]
       entry_SYSCALL_64_after_hwframe
           11.52%
                entry_SYSCALL_64_after_hwframe
                do_syscall_64
                __x64_sys_madvise
                do_madvise.part.0
                zap_page_range
                unmap_single_vma
                unmap_page_range
                page_remove_rmap
                deferred_split_huge_page
                __lock_text_start
                native_queued_spin_lock_slowpath

If THP can't be removed from rmap as whole THP, partial THP will be
removed from rmap by removing sub-pages from rmap.  Even the THP head page
is added to deferred queue already, the split_queue_lock will be acquired
and check whether the THP head page is in the queue already.  Thus, the
contention of split_queue_lock is raised.

Before acquire split_queue_lock, check and bail out early if the THP
head page is in the queue already. The checking without holding
split_queue_lock could race with deferred_split_scan, but it doesn't
impact the correctness here.

Test result of building kernel with ld.lld:
commit 7b5a0b664ebe (parent commit of f35b5d7d676e):
time -f "\t%E real,\t%U user,\t%S sys" make LD=ld.lld -skj96 allmodconfig all
        6:07.99 real,   26367.77 user,  5063.35 sys

commit f35b5d7d676e:
time -f "\t%E real,\t%U user,\t%S sys" make LD=ld.lld -skj96 allmodconfig all
        7:22.15 real,   26235.03 user,  12504.55 sys

commit f35b5d7d676e with the fixing patch:
time -f "\t%E real,\t%U user,\t%S sys" make LD=ld.lld -skj96 allmodconfig all
        6:08.49 real,   26520.15 user,  5047.91 sys

Link: https://lkml.kernel.org/r/20221223135207.2275317-1-fengwei.yin@intel.com
Signed-off-by: Yin Fengwei 
Tested-by: Nathan Chancellor 
Acked-by: David Rientjes 
Reviewed-by: "Huang, Ying" 
Cc: Feng Tang 
Cc: Matthew Wilcox 
Cc: Rik van Riel 
Cc: Xing Zhengjun 
Cc: Yang Shi 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

mm/huge_memory.c: don't discard hugepage if other processes are mapping it

2021-07-14T14:53:47+00:00

[ Upstream commit babbbdd08af98a59089334eb3effbed5a7a0cf7f ]

If other processes are mapping any other subpages of the hugepage, i.e.
in pte-mapped thp case, page_mapcount() will return 1 incorrectly.  Then
we would discard the page while other processes are still mapping it.  Fix
it by using total_mapcount() which can tell whether other processes are
still mapping it.

Link: https://lkml.kernel.org/r/20210511134857.1581273-6-linmiaohe@huawei.com
Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called")
Reviewed-by: Yang Shi 
Signed-off-by: Miaohe Lin 
Cc: Alexey Dobriyan 
Cc: "Aneesh Kumar K . V" 
Cc: Anshuman Khandual 
Cc: David Hildenbrand 
Cc: Hugh Dickins 
Cc: Johannes Weiner 
Cc: Kirill A. Shutemov 
Cc: Matthew Wilcox 
Cc: Minchan Kim 
Cc: Ralph Campbell 
Cc: Rik van Riel 
Cc: Song Liu 
Cc: William Kucharski 
Cc: Zi Yan 
Cc: Mike Kravetz 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

mm: thp: replace DEBUG_VM BUG with VM_WARN when unmap fails for split

2021-06-30T12:47:53+00:00

[ Upstream commit 504e070dc08f757bccaed6d05c0f53ecbfac8a23 ]

When debugging the bug reported by Wang Yugui [1], try_to_unmap() may
fail, but the first VM_BUG_ON_PAGE() just checks page_mapcount() however
it may miss the failure when head page is unmapped but other subpage is
mapped.  Then the second DEBUG_VM BUG() that check total mapcount would
catch it.  This may incur some confusion.

As this is not a fatal issue, so consolidate the two DEBUG_VM checks
into one VM_WARN_ON_ONCE_PAGE().

[1] https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/

Link: https://lkml.kernel.org/r/d0f0db68-98b8-ebfb-16dc-f29df24cf012@google.com
Signed-off-by: Yang Shi 
Reviewed-by: Zi Yan 
Acked-by: Kirill A. Shutemov 
Signed-off-by: Hugh Dickins 
Cc: Alistair Popple 
Cc: Jan Kara 
Cc: Jue Wang 
Cc: "Matthew Wilcox (Oracle)" 
Cc: Miaohe Lin 
Cc: Minchan Kim 
Cc: Naoya Horiguchi 
Cc: Oscar Salvador 
Cc: Peter Xu 
Cc: Ralph Campbell 
Cc: Shakeel Butt 
Cc: Wang Yugui 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 

Note on stable backport: fixed up variables in split_huge_page_to_list(),
and fixed up the conflict on ttu_flags in unmap_page().

Signed-off-by: Hugh Dickins 
Signed-off-by: Greg Kroah-Hartman

mm/thp: try_to_unmap() use TTU_SYNC for safe splitting

2021-06-30T12:47:52+00:00

[ Upstream commit 732ed55823fc3ad998d43b86bf771887bcc5ec67 ]

Stressing huge tmpfs often crashed on unmap_page()'s VM_BUG_ON_PAGE
(!unmap_success): with dump_page() showing mapcount:1, but then its raw
struct page output showing _mapcount ffffffff i.e.  mapcount 0.

And even if that particular VM_BUG_ON_PAGE(!unmap_success) is removed,
it is immediately followed by a VM_BUG_ON_PAGE(compound_mapcount(head)),
and further down an IS_ENABLED(CONFIG_DEBUG_VM) total_mapcount BUG():
all indicative of some mapcount difficulty in development here perhaps.
But the !CONFIG_DEBUG_VM path handles the failures correctly and
silently.

I believe the problem is that once a racing unmap has cleared pte or
pmd, try_to_unmap_one() may skip taking the page table lock, and emerge
from try_to_unmap() before the racing task has reached decrementing
mapcount.

Instead of abandoning the unsafe VM_BUG_ON_PAGE(), and the ones that
follow, use PVMW_SYNC in try_to_unmap_one() in this case: adding
TTU_SYNC to the options, and passing that from unmap_page().

When CONFIG_DEBUG_VM, or for non-debug too? Consensus is to do the same
for both: the slight overhead added should rarely matter, except perhaps
if splitting sparsely-populated multiply-mapped shmem.  Once confident
that bugs are fixed, TTU_SYNC here can be removed, and the race
tolerated.

Link: https://lkml.kernel.org/r/c1e95853-8bcd-d8fd-55fa-e7f2488e78f@google.com
Fixes: fec89c109f3a ("thp: rewrite freeze_page()/unfreeze_page() with generic rmap walkers")
Signed-off-by: Hugh Dickins 
Cc: Alistair Popple 
Cc: Jan Kara 
Cc: Jue Wang 
Cc: Kirill A. Shutemov 
Cc: "Matthew Wilcox (Oracle)" 
Cc: Miaohe Lin 
Cc: Minchan Kim 
Cc: Naoya Horiguchi 
Cc: Oscar Salvador 
Cc: Peter Xu 
Cc: Ralph Campbell 
Cc: Shakeel Butt 
Cc: Wang Yugui 
Cc: Yang Shi 
Cc: Zi Yan 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 

Note on stable backport: upstream TTU_SYNC 0x10 takes the value which
5.11 commit 013339df116c ("mm/rmap: always do TTU_IGNORE_ACCESS") freed.
It is very tempting to backport that commit (as 5.10 already did) and
make no change here; but on reflection, good as that commit is, I'm
reluctant to include any possible side-effect of it in this series.

Signed-off-by: Hugh Dickins 
Signed-off-by: Greg Kroah-Hartman

mm/thp: make is_huge_zero_pmd() safe and quicker

2021-06-30T12:47:52+00:00

commit 3b77e8c8cde581dadab9a0f1543a347e24315f11 upstream.

Most callers of is_huge_zero_pmd() supply a pmd already verified
present; but a few (notably zap_huge_pmd()) do not - it might be a pmd
migration entry, in which the pfn is encoded differently from a present
pmd: which might pass the is_huge_zero_pmd() test (though not on x86,
since L1TF forced us to protect against that); or perhaps even crash in
pmd_page() applied to a swap-like entry.

Make it safe by adding pmd_present() check into is_huge_zero_pmd()
itself; and make it quicker by saving huge_zero_pfn, so that
is_huge_zero_pmd() will not need to do that pmd_page() lookup each time.

__split_huge_pmd_locked() checked pmd_trans_huge() before: that worked,
but is unnecessary now that is_huge_zero_pmd() checks present.

Link: https://lkml.kernel.org/r/21ea9ca-a1f5-8b90-5e88-95fb1c49bbfa@google.com
Fixes: e71769ae5260 ("mm: enable thp migration for shmem thp")
Signed-off-by: Hugh Dickins 
Acked-by: Kirill A. Shutemov 
Reviewed-by: Yang Shi 
Cc: Alistair Popple 
Cc: Jan Kara 
Cc: Jue Wang 
Cc: "Matthew Wilcox (Oracle)" 
Cc: Miaohe Lin 
Cc: Minchan Kim 
Cc: Naoya Horiguchi 
Cc: Oscar Salvador 
Cc: Peter Xu 
Cc: Ralph Campbell 
Cc: Shakeel Butt 
Cc: Wang Yugui 
Cc: Zi Yan 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/thp: fix __split_huge_pmd_locked() on shmem migration entry

2021-06-30T12:47:52+00:00

[ Upstream commit 99fa8a48203d62b3743d866fc48ef6abaee682be ]

Patch series "mm/thp: fix THP splitting unmap BUGs and related", v10.

Here is v2 batch of long-standing THP bug fixes that I had not got
around to sending before, but prompted now by Wang Yugui's report
https://lore.kernel.org/linux-mm/20210412180659.B9E3.409509F4@e16-tech.com/

Wang Yugui has tested a rollup of these fixes applied to 5.10.39, and
they have done no harm, but have *not* fixed that issue: something more
is needed and I have no idea of what.

This patch (of 7):

Stressing huge tmpfs page migration racing hole punch often crashed on
the VM_BUG_ON(!pmd_present) in pmdp_huge_clear_flush(), with DEBUG_VM=y
kernel; or shortly afterwards, on a bad dereference in
__split_huge_pmd_locked() when DEBUG_VM=n.  They forgot to allow for pmd
migration entries in the non-anonymous case.

Full disclosure: those particular experiments were on a kernel with more
relaxed mmap_lock and i_mmap_rwsem locking, and were not repeated on the
vanilla kernel: it is conceivable that stricter locking happens to avoid
those cases, or makes them less likely; but __split_huge_pmd_locked()
already allowed for pmd migration entries when handling anonymous THPs,
so this commit brings the shmem and file THP handling into line.

And while there: use old_pmd rather than _pmd, as in the following
blocks; and make it clearer to the eye that the !vma_is_anonymous()
block is self-contained, making an early return after accounting for
unmapping.

Link: https://lkml.kernel.org/r/af88612-1473-2eaa-903-8d1a448b26@google.com
Link: https://lkml.kernel.org/r/dd221a99-efb3-cd1d-6256-7e646af29314@google.com
Fixes: e71769ae5260 ("mm: enable thp migration for shmem thp")
Signed-off-by: Hugh Dickins 
Cc: Kirill A. Shutemov 
Cc: Yang Shi 
Cc: Wang Yugui 
Cc: "Matthew Wilcox (Oracle)" 
Cc: Naoya Horiguchi 
Cc: Alistair Popple 
Cc: Ralph Campbell 
Cc: Zi Yan 
Cc: Miaohe Lin 
Cc: Minchan Kim 
Cc: Jue Wang 
Cc: Peter Xu 
Cc: Jan Kara 
Cc: Shakeel Butt 
Cc: Oscar Salvador 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 

Note on stable backport: this commit made intervening cleanups in
pmdp_huge_clear_flush() redundant: here it's rediffed to skip them.

Signed-off-by: Hugh Dickins 
Signed-off-by: Greg Kroah-Hartman

mm: thp: fix MADV_REMOVE deadlock on shmem THP

2021-02-10T08:25:31+00:00

commit 1c2f67308af4c102b4e1e6cd6f69819ae59408e0 upstream.

Sergey reported deadlock between kswapd correctly doing its usual
lock_page(page) followed by down_read(page->mapping->i_mmap_rwsem), and
madvise(MADV_REMOVE) on an madvise(MADV_HUGEPAGE) area doing
down_write(page->mapping->i_mmap_rwsem) followed by lock_page(page).

This happened when shmem_fallocate(punch hole)'s unmap_mapping_range()
reaches zap_pmd_range()'s call to __split_huge_pmd().  The same deadlock
could occur when partially truncating a mapped huge tmpfs file, or using
fallocate(FALLOC_FL_PUNCH_HOLE) on it.

__split_huge_pmd()'s page lock was added in 5.8, to make sure that any
concurrent use of reuse_swap_page() (holding page lock) could not catch
the anon THP's mapcounts and swapcounts while they were being split.

Fortunately, reuse_swap_page() is never applied to a shmem or file THP
(not even by khugepaged, which checks PageSwapCache before calling), and
anonymous THPs are never created in shmem or file areas: so that
__split_huge_pmd()'s page lock can only be necessary for anonymous THPs,
on which there is no risk of deadlock with i_mmap_rwsem.

Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2101161409470.2022@eggly.anvils
Fixes: c444eb564fb1 ("mm: thp: make the THP mapcount atomic against __split_huge_pmd_locked()")
Signed-off-by: Hugh Dickins 
Reported-by: Sergey Senozhatsky 
Reviewed-by: Andrea Arcangeli 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/userfaultfd: do not access vma->vm_mm after calling handle_userfault()

2020-11-24T12:29:24+00:00

commit bfe8cc1db02ab243c62780f17fc57f65bde0afe1 upstream.

Alexander reported a syzkaller / KASAN finding on s390, see below for
complete output.

In do_huge_pmd_anonymous_page(), the pre-allocated pagetable will be
freed in some cases.  In the case of userfaultfd_missing(), this will
happen after calling handle_userfault(), which might have released the
mmap_lock.  Therefore, the following pte_free(vma->vm_mm, pgtable) will
access an unstable vma->vm_mm, which could have been freed or re-used
already.

For all architectures other than s390 this will go w/o any negative
impact, because pte_free() simply frees the page and ignores the
passed-in mm.  The implementation for SPARC32 would also access
mm->page_table_lock for pte_free(), but there is no THP support in
SPARC32, so the buggy code path will not be used there.

For s390, the mm->context.pgtable_list is being used to maintain the 2K
pagetable fragments, and operating on an already freed or even re-used
mm could result in various more or less subtle bugs due to list /
pagetable corruption.

Fix this by calling pte_free() before handle_userfault(), similar to how
it is already done in __do_huge_pmd_anonymous_page() for the WRITE /
non-huge_zero_page case.

Commit 6b251fc96cf2c ("userfaultfd: call handle_userfault() for
userfaultfd_missing() faults") actually introduced both, the
do_huge_pmd_anonymous_page() and also __do_huge_pmd_anonymous_page()
changes wrt to calling handle_userfault(), but only in the latter case
it put the pte_free() before calling handle_userfault().

  BUG: KASAN: use-after-free in do_huge_pmd_anonymous_page+0xcda/0xd90 mm/huge_memory.c:744
  Read of size 8 at addr 00000000962d6988 by task syz-executor.0/9334

  CPU: 1 PID: 9334 Comm: syz-executor.0 Not tainted 5.10.0-rc1-syzkaller-07083-g4c9720875573 #0
  Hardware name: IBM 3906 M04 701 (KVM/Linux)
  Call Trace:
    do_huge_pmd_anonymous_page+0xcda/0xd90 mm/huge_memory.c:744
    create_huge_pmd mm/memory.c:4256 [inline]
    __handle_mm_fault+0xe6e/0x1068 mm/memory.c:4480
    handle_mm_fault+0x288/0x748 mm/memory.c:4607
    do_exception+0x394/0xae0 arch/s390/mm/fault.c:479
    do_dat_exception+0x34/0x80 arch/s390/mm/fault.c:567
    pgm_check_handler+0x1da/0x22c arch/s390/kernel/entry.S:706
    copy_from_user_mvcos arch/s390/lib/uaccess.c:111 [inline]
    raw_copy_from_user+0x3a/0x88 arch/s390/lib/uaccess.c:174
    _copy_from_user+0x48/0xa8 lib/usercopy.c:16
    copy_from_user include/linux/uaccess.h:192 [inline]
    __do_sys_sigaltstack kernel/signal.c:4064 [inline]
    __s390x_sys_sigaltstack+0xc8/0x240 kernel/signal.c:4060
    system_call+0xe0/0x28c arch/s390/kernel/entry.S:415

  Allocated by task 9334:
    slab_alloc_node mm/slub.c:2891 [inline]
    slab_alloc mm/slub.c:2899 [inline]
    kmem_cache_alloc+0x118/0x348 mm/slub.c:2904
    vm_area_dup+0x9c/0x2b8 kernel/fork.c:356
    __split_vma+0xba/0x560 mm/mmap.c:2742
    split_vma+0xca/0x108 mm/mmap.c:2800
    mlock_fixup+0x4ae/0x600 mm/mlock.c:550
    apply_vma_lock_flags+0x2c6/0x398 mm/mlock.c:619
    do_mlock+0x1aa/0x718 mm/mlock.c:711
    __do_sys_mlock2 mm/mlock.c:738 [inline]
    __s390x_sys_mlock2+0x86/0xa8 mm/mlock.c:728
    system_call+0xe0/0x28c arch/s390/kernel/entry.S:415

  Freed by task 9333:
    slab_free mm/slub.c:3142 [inline]
    kmem_cache_free+0x7c/0x4b8 mm/slub.c:3158
    __vma_adjust+0x7b2/0x2508 mm/mmap.c:960
    vma_merge+0x87e/0xce0 mm/mmap.c:1209
    userfaultfd_release+0x412/0x6b8 fs/userfaultfd.c:868
    __fput+0x22c/0x7a8 fs/file_table.c:281
    task_work_run+0x200/0x320 kernel/task_work.c:151
    tracehook_notify_resume include/linux/tracehook.h:188 [inline]
    do_notify_resume+0x100/0x148 arch/s390/kernel/signal.c:538
    system_call+0xe6/0x28c arch/s390/kernel/entry.S:416

  The buggy address belongs to the object at 00000000962d6948 which belongs to the cache vm_area_struct of size 200
  The buggy address is located 64 bytes inside of 200-byte region [00000000962d6948, 00000000962d6a10)
  The buggy address belongs to the page: page:00000000313a09fe refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x962d6 flags: 0x3ffff00000000200(slab)
  raw: 3ffff00000000200 000040000257e080 0000000c0000000c 000000008020ba00
  raw: 0000000000000000 000f001e00000000 ffffffff00000001 0000000096959501
  page dumped because: kasan: bad access detected
  page->mem_cgroup:0000000096959501

  Memory state around the buggy address:
   00000000962d6880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
   00000000962d6900: 00 fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb
  >00000000962d6980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                        ^
   00000000962d6a00: fb fb fc fc fc fc fc fc fc fc 00 00 00 00 00 00
   00000000962d6a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ==================================================================

Fixes: 6b251fc96cf2c ("userfaultfd: call handle_userfault() for userfaultfd_missing() faults")
Reported-by: Alexander Egorenkov 
Signed-off-by: Gerald Schaefer 
Signed-off-by: Andrew Morton 
Cc: Andrea Arcangeli 
Cc: Heiko Carstens 
Cc: 	[4.3+]
Link: https://lkml.kernel.org/r/20201110190329.11920-1-gerald.schaefer@linux.ibm.com
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/page_owner: change split_page_owner to take a count

2020-10-29T08:57:52+00:00

[ Upstream commit 8fb156c9ee2db94f7127c930c89917634a1a9f56 ]

The implementation of split_page_owner() prefers a count rather than the
old order of the page.  When we support a variable size THP, we won't
have the order at this point, but we will have the number of pages.
So change the interface to what the caller and callee would prefer.

Signed-off-by: Matthew Wilcox (Oracle) 
Signed-off-by: Andrew Morton 
Reviewed-by: SeongJae Park 
Acked-by: Kirill A. Shutemov 
Cc: Huang Ying 
Link: https://lkml.kernel.org/r/20200908195539.25896-4-willy@infradead.org
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin