• Naoya Horiguchi's avatar
    mm/memory-failure.c: fix memory leak in successful soft offlining · f15bdfa8
    Naoya Horiguchi authored
    After a successful page migration by soft offlining, the source page is
    not properly freed and it's never reusable even if we unpoison it
    afterward.
    
    This is caused by the race between freeing page and setting PG_hwpoison.
    In successful soft offlining, the source page is put (and the refcount
    becomes 0) by putback_lru_page() in unmap_and_move(), where it's linked
    to pagevec and actual freeing back to buddy is delayed.  So if
    PG_hwpoison is set for the page before freeing, the freeing does not
    functions as expected (in such case freeing aborts in
    free_pages_prepare() check.)
    
    This patch tries to make sure to free the source page before setting
    PG_hwpoison on it.  To avoid reallocating, the page keeps
    MIGRATE_ISOLATE until after setting PG_hwpoison.
    
    This patch also removes obsolete comments about "keeping elevated
    refcount" because what they say is not true.  Unlike memory_failure(),
    soft_offline_page() uses no special page isolation code, and the
    soft-offlined pages have no elevated.
    Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Mel Gorman <mel@csn.ul.ie>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    f15bdfa8
memory-failure.c 44.8 KB