From: Michal Hocko <mhocko@xxxxxxx>
Subject: memcg, shmem: fix shmem migration to use lrucare
It has been reported that 965GM might trigger
VM_BUG_ON_PAGE(!lrucare && PageLRU(oldpage), oldpage)
in mem_cgroup_migrate when shmem wants to replace a swap cache page
because of shmem_should_replace_page (the page is allocated from an
inappropriate zone). shmem_replace_page expects that the oldpage is not
on LRU list and calls mem_cgroup_migrate without lrucare. This is
obviously incorrect because swapcache pages might be on the LRU list (e.g.
swapin readahead page).
Fix this by enabling lrucare for the migration in shmem_replace_page.
Also clarify that lrucare should be used even if one of the pages might be
on LRU list.
The BUG_ON will trigger only when CONFIG_DEBUG_VM is enabled but even
without that the migration code might leave the old page on an
inappropriate memcg' LRU which is not that critical because the page would
get removed with its last reference but it is still confusing.
Fixes: 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API")
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Reported-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reported-by: Dave Airlie <airlied@xxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.17+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 2 +-
mm/shmem.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff -puN mm/memcontrol.c~memcg-shmem-fix-shmem-migration-to-use-lrucare mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-shmem-fix-shmem-migration-to-use-lrucare
+++ a/mm/memcontrol.c
@@ -5773,7 +5773,7 @@ void mem_cgroup_uncharge_list(struct lis
* mem_cgroup_migrate - migrate a charge to another page
* @oldpage: currently charged page
* @newpage: page to transfer the charge to
- * @lrucare: both pages might be on the LRU already
+ * @lrucare: either or both pages might be on the LRU already
*
* Migrate the charge from @oldpage to @newpage.
*
diff -puN mm/shmem.c~memcg-shmem-fix-shmem-migration-to-use-lrucare mm/shmem.c
--- a/mm/shmem.c~memcg-shmem-fix-shmem-migration-to-use-lrucare
+++ a/mm/shmem.c
@@ -1013,7 +1013,7 @@ static int shmem_replace_page(struct pag
*/
oldpage = newpage;
} else {
- mem_cgroup_migrate(oldpage, newpage, false);
+ mem_cgroup_migrate(oldpage, newpage, true);
lru_cache_add_anon(newpage);
*pagep = newpage;
}
_
--
To unsubscribe from this list: send the line "unsubscribe stable" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html