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
......@@ -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;
}
......
......@@ -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;
}
......
......@@ -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;
}
......
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