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authorHugh Dickins <hughd@google.com>2014-08-28 19:35:35 +0100
committerJiri Slaby <jslaby@suse.cz>2014-09-26 11:52:06 +0200
commit1d08848674752a433634f5c144500447de8ab727 (patch)
tree7d80c34eb10fa1ae74d42179aea75ba3df1ee343 /mm/slob.c
parent335886a3689bb3be6bc37f6601006ee20ccd80a0 (diff)
mm/memory.c: use entry = ACCESS_ONCE(*pte) in handle_pte_fault()
commit c0d73261f5c1355a35b8b40e871d31578ce0c044 upstream. Use ACCESS_ONCE() in handle_pte_fault() when getting the entry or orig_pte upon which all subsequent decisions and pte_same() tests will be made. I have no evidence that its lack is responsible for the mm/filemap.c:202 BUG_ON(page_mapped(page)) in __delete_from_page_cache() found by trinity, and I am not optimistic that it will fix it. But I have found no other explanation, and ACCESS_ONCE() here will surely not hurt. If gcc does re-access the pte before passing it down, then that would be disastrous for correct page fault handling, and certainly could explain the page_mapped() BUGs seen (concurrent fault causing page to be mapped in a second time on top of itself: mapcount 2 for a single pte). Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'mm/slob.c')
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