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Commit 50de1dd9 authored by Daisuke Nishimura's avatar Daisuke Nishimura Committed by Linus Torvalds
Browse files

memcg: fix memory migration of shmem swapcache 



In the current implementation mem_cgroup_end_migration() decides whether
the page migration has succeeded or not by checking "oldpage->mapping".

But if we are tring to migrate a shmem swapcache, the page->mapping of it
is NULL from the begining, so the check would be invalid.  As a result,
mem_cgroup_end_migration() assumes the migration has succeeded even if
it's not, so "newpage" would be freed while it's not uncharged.

This patch fixes it by passing mem_cgroup_end_migration() the result of
the page migration.

Signed-off-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: default avatarBalbir Singh <balbir@linux.vnet.ibm.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 17295c88

include/linux/memcontrol.h

+2 −3
Original line number Diff line number Diff line
@@ -98,7 +98,7 @@ extern int 
mem_cgroup_prepare_migration(struct page *page,

	struct page *newpage, struct mem_cgroup **ptr);

extern void mem_cgroup_end_migration(struct mem_cgroup *mem,

	struct page *oldpage, struct page *newpage);

	struct page *oldpage, struct page *newpage, bool migration_ok);



/*

 * For memory reclaim.
@@ -251,8 +251,7 @@ mem_cgroup_prepare_migration(struct page *page, struct page *newpage, 
}



static inline void mem_cgroup_end_migration(struct mem_cgroup *mem,

					struct page *oldpage,

					struct page *newpage)

		struct page *oldpage, struct page *newpage, bool migration_ok)

{

}

mm/memcontrol.c

+2 −3
Original line number Diff line number Diff line
@@ -2896,7 +2896,7 @@ int mem_cgroup_prepare_migration(struct page *page, 


/* remove redundant charge if migration failed*/

void mem_cgroup_end_migration(struct mem_cgroup *mem,

	struct page *oldpage, struct page *newpage)

	struct page *oldpage, struct page *newpage, bool migration_ok)

{

	struct page *used, *unused;

	struct page_cgroup *pc;
@@ -2905,8 +2905,7 @@ void mem_cgroup_end_migration(struct mem_cgroup *mem, 
		return;

	/* blocks rmdir() */

	cgroup_exclude_rmdir(&mem->css);

	/* at migration success, oldpage->mapping is NULL. */

	if (oldpage->mapping) {

	if (!migration_ok) {

		used = oldpage;

		unused = newpage;

	} else {

mm/migrate.c

+1 −1
Original line number Diff line number Diff line
@@ -768,7 +768,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 


uncharge:

	if (!charge)

		mem_cgroup_end_migration(mem, page, newpage);

		mem_cgroup_end_migration(mem, page, newpage, rc == 0);

unlock:

	unlock_page(page);