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mm, thp: fix collapsing of hugepages on madvise 

commit 6d50e60cd2edb5a57154db5a6f64eef5aa59b751 upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[ luis: backported to 3.16:
  - use VM_BUG_ON() instead of VM_BUG_ON_VMA() ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
This commit is contained in:
David Rientjes 2014-10-29 14:50:31 -07:00 committed by syphyr
parent 573f2eee1f
commit 8d55e44b36
3 changed files with 20 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
include/linux/khugepaged.h
View File

@ -6,7 +6,8 @@
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
extern int __khugepaged_enter(struct mm_struct *mm);
extern void __khugepaged_exit(struct mm_struct *mm);
extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma);
extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags);
#define khugepaged_enabled() \
(transparent_hugepage_flags & \
@ -35,13 +36,13 @@ static inline void khugepaged_exit(struct mm_struct *mm)
__khugepaged_exit(mm);
}
static inline int khugepaged_enter(struct vm_area_struct *vma)
static inline int khugepaged_enter(struct vm_area_struct *vma,
unsigned long vm_flags)
{
if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
if ((khugepaged_always() ||
(khugepaged_req_madv() &&
vma->vm_flags & VM_HUGEPAGE)) &&
!(vma->vm_flags & VM_NOHUGEPAGE))
(khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) &&
!(vm_flags & VM_NOHUGEPAGE))
if (__khugepaged_enter(vma->vm_mm))
return -ENOMEM;
return 0;
@ -54,11 +55,13 @@ static inline int khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
static inline void khugepaged_exit(struct mm_struct *mm)
{
}
static inline int khugepaged_enter(struct vm_area_struct *vma)
static inline int khugepaged_enter(struct vm_area_struct *vma,
unsigned long vm_flags)
{
return 0;
}
static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma)
static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags)
{
return 0;
}

11
mm/huge_memory.c
View File

@ -788,7 +788,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
if (haddr >= vma->vm_start && haddr + HPAGE_PMD_SIZE <= vma->vm_end) {
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()) {
@ -1925,7 +1925,7 @@ 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:
@ -2026,7 +2026,8 @@ 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)
@ -2038,11 +2039,11 @@ 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->vm_flags & VM_NO_THP);
VM_BUG_ON(vm_flags & VM_NO_THP);
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;
}

8
mm/mmap.c
View File

@ -1076,7 +1076,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
end, prev->vm_pgoff, NULL);
if (err)
return NULL;
khugepaged_enter_vma_merge(prev);
khugepaged_enter_vma_merge(prev, vm_flags);
return prev;
}
@ -1095,7 +1095,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
next->vm_pgoff - pglen, NULL);
if (err)
return NULL;
khugepaged_enter_vma_merge(area);
khugepaged_enter_vma_merge(area, vm_flags);
return area;
}
@ -2260,7 +2260,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
}
}
vma_unlock_anon_vma(vma);
khugepaged_enter_vma_merge(vma);
khugepaged_enter_vma_merge(vma, vma->vm_flags);
validate_mm(vma->vm_mm);
return error;
}
@ -2339,7 +2339,7 @@ int expand_downwards(struct vm_area_struct *vma,
}
}
vma_unlock_anon_vma(vma);
khugepaged_enter_vma_merge(vma);
khugepaged_enter_vma_merge(vma, vma->vm_flags);
validate_mm(vma->vm_mm);
return error;
}