diff options
author | Andrea Arcangeli <aarcange@redhat.com> | 2011-04-27 22:26:45 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-04-28 18:28:20 (GMT) |
commit | 78f11a255749d09025f54d4e2df4fbcb031530e2 (patch) | |
tree | 20f8ffaf8548d963ffb519631f5c7d7372e9ca42 /mm/huge_memory.c | |
parent | 6d4831c283530a5f2c6bd8172c13efa236eb149d (diff) | |
download | linux-78f11a255749d09025f54d4e2df4fbcb031530e2.tar.xz |
mm: thp: fix /dev/zero MAP_PRIVATE and vm_flags cleanups
The huge_memory.c THP page fault was allowed to run if vm_ops was null
(which would succeed for /dev/zero MAP_PRIVATE, as the f_op->mmap wouldn't
setup a special vma->vm_ops and it would fallback to regular anonymous
memory) but other THP logics weren't fully activated for vmas with vm_file
not NULL (/dev/zero has a not NULL vma->vm_file).
So this removes the vm_file checks so that /dev/zero also can safely use
THP (the other albeit safer approach to fix this bug would have been to
prevent the THP initial page fault to run if vm_file was set).
After removing the vm_file checks, this also makes huge_memory.c stricter
in khugepaged for the DEBUG_VM=y case. It doesn't replace the vm_file
check with a is_pfn_mapping check (but it keeps checking for VM_PFNMAP
under VM_BUG_ON) because for a is_cow_mapping() mapping VM_PFNMAP should
only be allowed to exist before the first page fault, and in turn when
vma->anon_vma is null (so preventing khugepaged registration). So I tend
to think the previous comment saying if vm_file was set, VM_PFNMAP might
have been set and we could still be registered in khugepaged (despite
anon_vma was not NULL to be registered in khugepaged) was too paranoid.
The is_linear_pfn_mapping check is also I think superfluous (as described
by comment) but under DEBUG_VM it is safe to stay.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=33682
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Caspar Zhang <bugs@casparzhang.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: <stable@kernel.org> [2.6.38.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r-- | mm/huge_memory.c | 43 |
1 files changed, 24 insertions, 19 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 470dcda..83326ad 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1408,6 +1408,9 @@ out: return ret; } +#define VM_NO_THP (VM_SPECIAL|VM_INSERTPAGE|VM_MIXEDMAP|VM_SAO| \ + VM_HUGETLB|VM_SHARED|VM_MAYSHARE) + int hugepage_madvise(struct vm_area_struct *vma, unsigned long *vm_flags, int advice) { @@ -1416,11 +1419,7 @@ int hugepage_madvise(struct vm_area_struct *vma, /* * Be somewhat over-protective like KSM for now! */ - if (*vm_flags & (VM_HUGEPAGE | - VM_SHARED | VM_MAYSHARE | - VM_PFNMAP | VM_IO | VM_DONTEXPAND | - VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | - VM_MIXEDMAP | VM_SAO)) + if (*vm_flags & (VM_HUGEPAGE | VM_NO_THP)) return -EINVAL; *vm_flags &= ~VM_NOHUGEPAGE; *vm_flags |= VM_HUGEPAGE; @@ -1436,11 +1435,7 @@ int hugepage_madvise(struct vm_area_struct *vma, /* * Be somewhat over-protective like KSM for now! */ - if (*vm_flags & (VM_NOHUGEPAGE | - VM_SHARED | VM_MAYSHARE | - VM_PFNMAP | VM_IO | VM_DONTEXPAND | - VM_RESERVED | VM_HUGETLB | VM_INSERTPAGE | - VM_MIXEDMAP | VM_SAO)) + if (*vm_flags & (VM_NOHUGEPAGE | VM_NO_THP)) return -EINVAL; *vm_flags &= ~VM_HUGEPAGE; *vm_flags |= VM_NOHUGEPAGE; @@ -1574,10 +1569,14 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma) * page fault if needed. */ return 0; - if (vma->vm_file || vma->vm_ops) + if (vma->vm_ops) /* khugepaged not yet working on file or special mappings */ return 0; - VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); + /* + * If is_pfn_mapping() is true is_learn_pfn_mapping() must be + * true too, verify it here. + */ + VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->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) @@ -1828,12 +1827,15 @@ static void collapse_huge_page(struct mm_struct *mm, (vma->vm_flags & VM_NOHUGEPAGE)) goto out; - /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ - if (!vma->anon_vma || vma->vm_ops || vma->vm_file) + if (!vma->anon_vma || vma->vm_ops) goto out; if (is_vma_temporary_stack(vma)) goto out; - VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); + /* + * If is_pfn_mapping() is true is_learn_pfn_mapping() must be + * true too, verify it here. + */ + VM_BUG_ON(is_linear_pfn_mapping(vma) || vma->vm_flags & VM_NO_THP); pgd = pgd_offset(mm, address); if (!pgd_present(*pgd)) @@ -2066,13 +2068,16 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, progress++; continue; } - /* VM_PFNMAP vmas may have vm_ops null but vm_file set */ - if (!vma->anon_vma || vma->vm_ops || vma->vm_file) + if (!vma->anon_vma || vma->vm_ops) goto skip; if (is_vma_temporary_stack(vma)) goto skip; - - VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma)); + /* + * If is_pfn_mapping() is true is_learn_pfn_mapping() + * must be true too, verify it here. + */ + VM_BUG_ON(is_linear_pfn_mapping(vma) || + vma->vm_flags & VM_NO_THP); hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK; hend = vma->vm_end & HPAGE_PMD_MASK; |