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mm, thp: fix collapsing of hugepages on madvise

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If an anonymous mapping is not allowed to fault thp memory and then
madvise(MADV_HUGEPAGE) is used after fault, khugepaged will never
collapse this memory into thp memory.

This occurs because the madvise(2) handler for thp, hugepage_madvise(),
clears VM_NOHUGEPAGE on the stack and it isn't stored in vma->vm_flags
until the final action of madvise_behavior().  This causes the
khugepaged_enter_vma_merge() to be a no-op in hugepage_madvise() when
the vma had previously had VM_NOHUGEPAGE set.

Fix this by passing the correct vma flags to the khugepaged mm slot
handler.  There's no chance khugepaged can run on this vma until after
madvise_behavior() returns since we hold mm->mmap_sem.

It would be possible to clear VM_NOHUGEPAGE directly from vma->vm_flags
in hugepage_advise(), but I didn't want to introduce special case
behavior into madvise_behavior().  I think it's best to just let it
always set vma->vm_flags itself.

Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Suleiman Souhlal <suleiman@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Rientjes
2014-10-29 14:50:31 -07:00
committed by Linus Torvalds
parent 47f29df7db
commit 6d50e60cd2
3 changed files with 20 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
mm/huge_memory.c
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@@ -803,7 +803,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
return VM_FAULT_FALLBACK;
if (unlikely(anon_vma_prepare(vma)))
return VM_FAULT_OOM;
if (unlikely(khugepaged_enter(vma)))
if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
return VM_FAULT_OOM;
if (!(flags & FAULT_FLAG_WRITE) &&
transparent_hugepage_use_zero_page()) {
@@ -1970,7 +1970,7 @@ int hugepage_madvise(struct vm_area_struct *vma,
* register it here without waiting a page fault that
* may not happen any time soon.
*/
if (unlikely(khugepaged_enter_vma_merge(vma)))
if (unlikely(khugepaged_enter_vma_merge(vma, *vm_flags)))
return -ENOMEM;
break;
case MADV_NOHUGEPAGE:
@@ -2071,7 +2071,8 @@ int __khugepaged_enter(struct mm_struct *mm)
return 0;
}
int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags)
{
unsigned long hstart, hend;
if (!vma->anon_vma)
@@ -2083,11 +2084,11 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
if (vma->vm_ops)
/* khugepaged not yet working on file or special mappings */
return 0;
VM_BUG_ON_VMA(vma->vm_flags & VM_NO_THP, vma);
VM_BUG_ON_VMA(vm_flags & VM_NO_THP, vma);
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart < hend)
return khugepaged_enter(vma);
return khugepaged_enter(vma, vm_flags);
return 0;
}