diff options
author | Johannes Weiner <jweiner@redhat.com> | 2012-01-12 20:18:38 -0500 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-01-12 23:13:06 -0500 |
commit | cfa449461e67b60df986170eecb089831fa9e49a (patch) | |
tree | ff40cff591e27250b91b2f1fb4409875f397b048 | |
parent | 0e574a932d2cab8eb3b02d21feb59f2c09154738 (diff) |
mm: memcg: lookup_page_cgroup (almost) never returns NULL
Pages have their corresponding page_cgroup descriptors set up before
they are used in userspace, and thus managed by a memory cgroup.
The only time where lookup_page_cgroup() can return NULL is in the
CONFIG_DEBUG_VM-only page sanity checking code that executes while
feeding pages into the page allocator for the first time.
Remove the NULL checks against lookup_page_cgroup() results from all
callsites where we know that corresponding page_cgroup descriptors must
be allocated, and add a comment to the callsite that actually does have
to check the return value.
[hughd@google.com: stop oops in mem_cgroup_update_page_stat()]
Signed-off-by: Johannes Weiner <jweiner@redhat.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | mm/memcontrol.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 93cb16d2b96a..a63ad141083c 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c | |||
@@ -1960,7 +1960,7 @@ void mem_cgroup_update_page_stat(struct page *page, | |||
1960 | bool need_unlock = false; | 1960 | bool need_unlock = false; |
1961 | unsigned long uninitialized_var(flags); | 1961 | unsigned long uninitialized_var(flags); |
1962 | 1962 | ||
1963 | if (unlikely(!pc)) | 1963 | if (mem_cgroup_disabled()) |
1964 | return; | 1964 | return; |
1965 | 1965 | ||
1966 | rcu_read_lock(); | 1966 | rcu_read_lock(); |
@@ -2735,8 +2735,6 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm, | |||
2735 | } | 2735 | } |
2736 | 2736 | ||
2737 | pc = lookup_page_cgroup(page); | 2737 | pc = lookup_page_cgroup(page); |
2738 | BUG_ON(!pc); /* XXX: remove this and move pc lookup into commit */ | ||
2739 | |||
2740 | ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &memcg, oom); | 2738 | ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &memcg, oom); |
2741 | if (ret || !memcg) | 2739 | if (ret || !memcg) |
2742 | return ret; | 2740 | return ret; |
@@ -3008,7 +3006,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype) | |||
3008 | * Check if our page_cgroup is valid | 3006 | * Check if our page_cgroup is valid |
3009 | */ | 3007 | */ |
3010 | pc = lookup_page_cgroup(page); | 3008 | pc = lookup_page_cgroup(page); |
3011 | if (unlikely(!pc || !PageCgroupUsed(pc))) | 3009 | if (unlikely(!PageCgroupUsed(pc))) |
3012 | return NULL; | 3010 | return NULL; |
3013 | 3011 | ||
3014 | lock_page_cgroup(pc); | 3012 | lock_page_cgroup(pc); |
@@ -3436,6 +3434,11 @@ static struct page_cgroup *lookup_page_cgroup_used(struct page *page) | |||
3436 | struct page_cgroup *pc; | 3434 | struct page_cgroup *pc; |
3437 | 3435 | ||
3438 | pc = lookup_page_cgroup(page); | 3436 | pc = lookup_page_cgroup(page); |
3437 | /* | ||
3438 | * Can be NULL while feeding pages into the page allocator for | ||
3439 | * the first time, i.e. during boot or memory hotplug; | ||
3440 | * or when mem_cgroup_disabled(). | ||
3441 | */ | ||
3439 | if (likely(pc) && PageCgroupUsed(pc)) | 3442 | if (likely(pc) && PageCgroupUsed(pc)) |
3440 | return pc; | 3443 | return pc; |
3441 | return NULL; | 3444 | return NULL; |