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author | Hugh Dickins <hughd@google.com> | 2018-12-01 01:10:16 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-01 01:56:15 +0300 |
commit | 173d9d9fd3ddae84c110fea8aedf1f26af6be9ec (patch) | |
tree | 88c2c654d6b0c60e437e814e217d520ebd1b5be6 /mm/khugepaged.c | |
parent | 906f9cdfc2a0800f13683f9e4ebdfd08c12ee81b (diff) | |
download | linux-173d9d9fd3ddae84c110fea8aedf1f26af6be9ec.tar.xz |
mm/huge_memory: splitting set mapping+index before unfreeze
Huge tmpfs stress testing has occasionally hit shmem_undo_range()'s
VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page).
Move the setting of mapping and index up before the page_ref_unfreeze()
in __split_huge_page_tail() to fix this: so that a page cache lookup
cannot get a reference while the tail's mapping and index are unstable.
In fact, might as well move them up before the smp_wmb(): I don't see an
actual need for that, but if I'm missing something, this way round is
safer than the other, and no less efficient.
You might argue that VM_BUG_ON_PAGE(page_to_pgoff(page) != index, page) is
misplaced, and should be left until after the trylock_page(); but left as
is has not crashed since, and gives more stringent assurance.
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261516380.2275@eggly.anvils
Fixes: e9b61f19858a5 ("thp: reintroduce split_huge_page()")
Requires: 605ca5ede764 ("mm/huge_memory.c: reorder operations in __split_huge_page_tail()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org> [4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/khugepaged.c')
0 files changed, 0 insertions, 0 deletions