mm/memory-failure.c: fix memory leak in successful soft offlining
authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Wed, 3 Jul 2013 22:02:37 +0000 (15:02 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 3 Jul 2013 23:07:31 +0000 (16:07 -0700)
commitf15bdfa802bfa5eb6b4b5a241b97ec9fa1204a35
treee490deddf30e0c73a663457c54d8961750ec72ee
parent9bde916bc73255dcee3d8aded990443675daa707
mm/memory-failure.c: fix memory leak in successful soft offlining

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: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/memory-failure.c