diff options
| author | Baolin Wang <baolin.wang@linux.alibaba.com> | 2026-08-18 10:47:26 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-09-01 20:26:21 -0700 |
| commit | 2fd4e7693674b17807a6d082feb01a3fbf86f5f8 (patch) | |
| tree | 16049d74a8125632a92251f011668f43a25acfe9 | |
| parent | 267bede12d3b108ca29997ce280e927a570ec97f (diff) | |
mm: fix incorrect vm_flags usage when checking allowable orders for tmpfs
Lance reported that when nothing else causes the mm to be considered for
khugepaged collapse, an MADV_HUGEPAGE-advised tmpfs VMA alone does not
trigger scanning.
After commit 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled()
into shmem_allowable_huge_orders()"), the shmem/tmpfs allowable order
check reads vma->flags directly. However, when MADV_HUGEPAGE is handled,
khugepaged_enter_vma() is called before the VMA's flags have been updated,
so the check uses stale flags and incorrectly rejects the VMA for
collapse. As a result, khugepaged does not collapse the tmpfs file into
PMD order in time.
Fix this by calling khugepaged_enter_vma() with the new VMA flags in
madvise_update_vma(). Meanwhile we can remove the khugepaged_enter_vma()
in hugepage_madvise().
Link: https://lore.kernel.org/7d5b5eb27be798f89d563b06254c947ff53db0b2.1787020910.git.baolin.wang@linux.alibaba.com
Fixes: 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled() into shmem_allowable_huge_orders()")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reported-by: Lance Yang <lance.yang@linux.dev>
Closes: https://lore.kernel.org/all/20260815181632.21453-1-lance.yang@linux.dev/
Suggested-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | mm/khugepaged.c | 6 | ||||
| -rw-r--r-- | mm/madvise.c | 8 |
2 files changed, 8 insertions, 6 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 11ff98d55c76..75639298efc2 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -454,12 +454,6 @@ int hugepage_madvise(struct vm_area_struct *vma, case MADV_HUGEPAGE: *vm_flags &= ~VM_NOHUGEPAGE; *vm_flags |= VM_HUGEPAGE; - /* - * If the vma become good for khugepaged to scan, - * register it here without waiting a page fault that - * may not happen any time soon. - */ - khugepaged_enter_vma(vma, *vm_flags); break; case MADV_NOHUGEPAGE: *vm_flags &= ~VM_HUGEPAGE; diff --git a/mm/madvise.c b/mm/madvise.c index 96f2387b2f46..eeee82cf2b3f 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -178,6 +178,14 @@ static int madvise_update_vma(vm_flags_t new_flags, /* vm_flags is protected by the mmap_lock held in write mode. */ vma_start_write(vma); vma->flags = new_vma_flags; + /* + * If the vma become good for khugepaged to scan, + * register it here without waiting a page fault that + * may not happen any time soon. + */ + if (vma_flags_test(&new_vma_flags, VMA_HUGEPAGE_BIT)) + khugepaged_enter_vma(vma, vma_flags_to_legacy(new_vma_flags)); + if (set_new_anon_name) return replace_anon_vma_name(vma, anon_name); |