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mm/shmem: restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE

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SHMEM_HUGE_DENY is for emergency use by the admin, to disable allocation
of shmem huge pages if, for example, a dangerous bug is found in their
usage: see "deny" in Documentation/mm/transhuge.rst.  An app using
madvise(,,MADV_COLLAPSE) should not be allowed to override it: restore its
precedence over shmem_huge_force.

Restore SHMEM_HUGE_DENY precedence over MADV_COLLAPSE.

Link: https://lkml.kernel.org/r/20221224082035.3197140-2-zokeefe@google.com
Fixes: 7c6c6cc4d3 ("mm/shmem: add flag to enforce shmem THP in hugepage_vma_check()")
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Suggested-by: Hugh Dickins <hughd@google.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Zach O'Keefe 2022-12-24 00:20:35 -08:00 committed by Andrew Morton
parent 52dc031088
commit 3de0c269ad
1 changed files with 2 additions and 4 deletions
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6
mm/shmem.c
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@ -478,12 +478,10 @@ bool shmem_is_huge(struct vm_area_struct *vma, struct inode *inode,
if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) || if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))) test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)))
return false; return false;
if (shmem_huge_force)
return true;
if (shmem_huge == SHMEM_HUGE_FORCE)
return true;
if (shmem_huge == SHMEM_HUGE_DENY) if (shmem_huge == SHMEM_HUGE_DENY)
return false; return false;
if (shmem_huge_force || shmem_huge == SHMEM_HUGE_FORCE)
return true;
switch (SHMEM_SB(inode->i_sb)->huge) { switch (SHMEM_SB(inode->i_sb)->huge) {
case SHMEM_HUGE_ALWAYS: case SHMEM_HUGE_ALWAYS: