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authorAndrea Arcangeli <aarcange@redhat.com>2011-04-27 15:26:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-04-28 11:28:20 -0700
commit78f11a255749d09025f54d4e2df4fbcb031530e2 (patch)
tree20f8ffaf8548d963ffb519631f5c7d7372e9ca42 /include
parent6d4831c283530a5f2c6bd8172c13efa236eb149d (diff)
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 'include')
-rw-r--r--include/linux/huge_mm.h2
-rw-r--r--include/linux/mm.h3
2 files changed, 3 insertions, 2 deletions
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index df29c8fde36b..8847c8c29791 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -117,7 +117,7 @@ static inline void vma_adjust_trans_huge(struct vm_area_struct *vma,
unsigned long end,
long adjust_next)
{
- if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
+ if (!vma->anon_vma || vma->vm_ops)
return;
__vma_adjust_trans_huge(vma, start, end, adjust_next);
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 692dbae6ffa7..2348db26bc3d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -137,7 +137,8 @@ extern unsigned int kobjsize(const void *objp);
#define VM_RandomReadHint(v) ((v)->vm_flags & VM_RAND_READ)
/*
- * special vmas that are non-mergable, non-mlock()able
+ * Special vmas that are non-mergable, non-mlock()able.
+ * Note: mm/huge_memory.c VM_NO_THP depends on this definition.
*/
#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_RESERVED | VM_PFNMAP)

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