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Commit 6d50e60c authored by David Rientjes's avatar David Rientjes Committed by Linus Torvalds
Browse files

mm, thp: fix collapsing of hugepages on madvise 



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: default avatarDavid Rientjes <rientjes@google.com>
Reported-by: default avatarSuleiman 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 47f29df7

include/linux/khugepaged.h

+10 −7
Original line number Diff line number Diff line
@@ -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;

}

mm/huge_memory.c

+6 −5
Original line number Diff line number Diff line
@@ -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;

}

mm/mmap.c

+4 −4
Original line number Diff line number Diff line
@@ -1080,7 +1080,7 @@ 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;

	}
@@ -1099,7 +1099,7 @@ 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;

	}
@@ -2208,7 +2208,7 @@ 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;

}
@@ -2277,7 +2277,7 @@ 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;

}