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authorAndrea Arcangeli <aarcange@redhat.com>2011-04-27 15:26:45 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2011-05-02 09:19:45 -0700
commit28785447dc596d0612513010e7bb23cce9c88e50 (patch)
tree7ebec01411c9a9d0a2e40e47bda0112253a5b02e /arch
parent649717e59e69038212d8e28bfa5fb66bfddb9dea (diff)
downloadlinux-2.6.38-lt-ux500-28785447dc596d0612513010e7bb23cce9c88e50.tar.gz
mm: thp: fix /dev/zero MAP_PRIVATE and vm_flags cleanups
commit 78f11a255749d09025f54d4e2df4fbcb031530e2 upstream. 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch')
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