The patch titled
Subject: mm: memcg: lookup_page_cgroup (almost) never returns NULL
has been removed from the -mm tree. Its filename was
mm-memcg-lookup_page_cgroup-almost-never-returns-null.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Johannes Weiner <jweiner@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx: stop oops in mem_cgroup_update_page_stat()]
Signed-off-by: Johannes Weiner <jweiner@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff -puN mm/memcontrol.c~mm-memcg-lookup_page_cgroup-almost-never-returns-null mm/memcontrol.c
--- a/mm/memcontrol.c~mm-memcg-lookup_page_cgroup-almost-never-returns-null
+++ a/mm/memcontrol.c
@@ -1960,7 +1960,7 @@ void mem_cgroup_update_page_stat(struct
bool need_unlock = false;
unsigned long uninitialized_var(flags);
- if (unlikely(!pc))
+ if (mem_cgroup_disabled())
return;
rcu_read_lock();
@@ -2735,8 +2735,6 @@ static int mem_cgroup_charge_common(stru
}
pc = lookup_page_cgroup(page);
- BUG_ON(!pc); /* XXX: remove this and move pc lookup into commit */
-
ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &memcg, oom);
if (ret || !memcg)
return ret;
@@ -3008,7 +3006,7 @@ __mem_cgroup_uncharge_common(struct page
* Check if our page_cgroup is valid
*/
pc = lookup_page_cgroup(page);
- if (unlikely(!pc || !PageCgroupUsed(pc)))
+ if (unlikely(!PageCgroupUsed(pc)))
return NULL;
lock_page_cgroup(pc);
@@ -3436,6 +3434,11 @@ static struct page_cgroup *lookup_page_c
struct page_cgroup *pc;
pc = lookup_page_cgroup(page);
+ /*
+ * Can be NULL while feeding pages into the page allocator for
+ * the first time, i.e. during boot or memory hotplug;
+ * or when mem_cgroup_disabled().
+ */
if (likely(pc) && PageCgroupUsed(pc))
return pc;
return NULL;
_
Patches currently in -mm which might be from jweiner@xxxxxxxxxx are
origin.patch
mm-add-extra-free-kbytes-tunable.patch
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