mm: thp: fix potential clearing to referenced flag in page_idle_clear_pte_refs_one()
commitf0849ac0b8e072073ec5fcc7fadd05a77434364e
authorYang Shi <yang.shi@linux.alibaba.com>
Thu, 5 Apr 2018 23:22:35 +0000 (5 16:22 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Fri, 6 Apr 2018 04:36:25 +0000 (5 21:36 -0700)
tree482a57307a9333e6c43a674056ea73e5643b26e8
parentc9e97a1997fbf3a1d18d4065c2ca381f0704d7e5
mm: thp: fix potential clearing to referenced flag in page_idle_clear_pte_refs_one()

For PTE-mapped THP, the compound THP has not been split to normal 4K
pages yet, the whole THP is considered referenced if any one of sub page
is referenced.

When walking PTE-mapped THP by pvmw, all relevant PTEs will be checked
to retrieve referenced bit.  But, the current code just returns the
result of the last PTE.  If the last PTE has not referenced, the
referenced flag will be cleared.

Just set referenced when ptep{pmdp}_clear_young_notify() returns true.

Link: http://lkml.kernel.org/r/1518212451-87134-1-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Reported-by: Gang Deng <gavin.dg@linux.alibaba.com>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/page_idle.c