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authorMichal Hocko <mhocko@suse.cz>2015-02-05 21:25:14 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2015-02-05 22:35:29 +0100
commitf5e03a4989e80a86f8b514659dca8539132e6e09 (patch)
tree7046479dc5ea0155f323e69f48b40aae1443b5d7
parentmm: export "high_memory" symbol on !MMU (diff)
downloadlinux-f5e03a4989e80a86f8b514659dca8539132e6e09.tar.xz
linux-f5e03a4989e80a86f8b514659dca8539132e6e09.zip
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@suse.cz> Reported-by: Chris Wilson <chris@chris-wilson.co.uk> Reported-by: Dave Airlie <airlied@gmail.com> Acked-by: Hugh Dickins <hughd@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: <stable@vger.kernel.org> [3.17+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/memcontrol.c2
-rw-r--r--mm/shmem.c2
2 files changed, 2 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 683b4782019b..2f6893c2f01b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5773,7 +5773,7 @@ void mem_cgroup_uncharge_list(struct list_head *page_list)
* 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 --git a/mm/shmem.c b/mm/shmem.c
index 73ba1df7c8ba..993e6ba689cc 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1013,7 +1013,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
*/
oldpage = newpage;
} else {
- mem_cgroup_migrate(oldpage, newpage, false);
+ mem_cgroup_migrate(oldpage, newpage, true);
lru_cache_add_anon(newpage);
*pagep = newpage;
}