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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-02-12 03:13:03 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-02-12 05:35:48 +0300
commit6b9116a652bd9e0e2994505cfaaa5f66deaa2a05 (patch)
tree9e9ae34807081abbec6ed856f4ed7c1f9b33d225 /mm/backing-dev.c
parent7eb391299419a03cbe0fa5ab0e6b0932e42c7a36 (diff)
downloadlinux-6b9116a652bd9e0e2994505cfaaa5f66deaa2a05.tar.xz
mm, dax: check for pmd_none() after split_huge_pmd()
DAX implements split_huge_pmd() by clearing pmd. This simple approach reduces memory overhead, as we don't need to deposit page table on huge page mapping to make split_huge_pmd() never-fail. PTE table can be allocated and populated later on page fault from backing store. But one side effect is that have to check if pmd is pmd_none() after split_huge_pmd(). In most places we do this already to deal with parallel MADV_DONTNEED. But I found two call sites which is not affected by MADV_DONTNEED (due down_write(mmap_sem)), but need to have the check to work with DAX properly. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Matthew Wilcox <willy@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/backing-dev.c')
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