• Mel Gorman's avatar
    mm: do not use unnecessary atomic operations when adding pages to the LRU · 6fb81a17
    Mel Gorman authored
    When adding pages to the LRU we clear the active bit unconditionally.
    As the page could be reachable from other paths we cannot use unlocked
    operations without risk of corruption such as a parallel
    mark_page_accessed.  This patch tests if is necessary to clear the
    active flag before using an atomic operation.  This potentially opens a
    tiny race when PageActive is checked as mark_page_accessed could be
    called after PageActive was checked.  The race already exists but this
    patch changes it slightly.  The consequence is that that the page may be
    promoted to the active list that might have been left on the inactive
    list before the patch.  It's too tiny a race and too marginal a
    consequence to always use atomic operations for.
    Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
    Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Jan Kara <jack@suse.cz>
    Cc: Michal Hocko <mhocko@suse.cz>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Theodore Ts'o <tytso@mit.edu>
    Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
swap.c 30.5 KB