The patch titled
Subject: memcg: zap mem_cgroup_lookup()
has been added to the -mm tree. Its filename is
memcg-zap-mem_cgroup_lookup.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/memcg-zap-mem_cgroup_lookup.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/memcg-zap-mem_cgroup_lookup.patch
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------------------------------------------------------
From: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Subject: memcg: zap mem_cgroup_lookup()
mem_cgroup_lookup() is a wrapper around mem_cgroup_from_id(), which checks
that id != 0 before issuing the function call. Today, there is no point
in this additional check apart from optimization, because there is no css
with id <= 0, so that css_from_id, called by mem_cgroup_from_id, will
return NULL for any id <= 0.
Since mem_cgroup_from_id is only called from mem_cgroup_lookup, let us zap
mem_cgroup_lookup, substituting calls to it with mem_cgroup_from_id and
moving the check if id > 0 to css_from_id.
Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 2 +-
mm/memcontrol.c | 24 ++++++++----------------
2 files changed, 9 insertions(+), 17 deletions(-)
diff -puN kernel/cgroup.c~memcg-zap-mem_cgroup_lookup kernel/cgroup.c
--- a/kernel/cgroup.c~memcg-zap-mem_cgroup_lookup
+++ a/kernel/cgroup.c
@@ -5451,7 +5451,7 @@ struct cgroup_subsys_state *css_tryget_o
struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
{
WARN_ON_ONCE(!rcu_read_lock_held());
- return idr_find(&ss->css_idr, id);
+ return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
}
#ifdef CONFIG_CGROUP_DEBUG
diff -puN mm/memcontrol.c~memcg-zap-mem_cgroup_lookup mm/memcontrol.c
--- a/mm/memcontrol.c~memcg-zap-mem_cgroup_lookup
+++ a/mm/memcontrol.c
@@ -460,6 +460,12 @@ static inline unsigned short mem_cgroup_
return memcg->css.id;
}
+/*
+ * A helper function to get mem_cgroup from ID. must be called under
+ * rcu_read_lock(). The caller is responsible for calling
+ * css_tryget_online() if the mem_cgroup is used for charging. (dropping
+ * refcnt from swap can be called against removed memcg.)
+ */
static inline struct mem_cgroup *mem_cgroup_from_id(unsigned short id)
{
struct cgroup_subsys_state *css;
@@ -2349,20 +2355,6 @@ static void cancel_charge(struct mem_cgr
}
/*
- * A helper function to get mem_cgroup from ID. must be called under
- * rcu_read_lock(). The caller is responsible for calling
- * css_tryget_online() if the mem_cgroup is used for charging. (dropping
- * refcnt from swap can be called against removed memcg.)
- */
-static struct mem_cgroup *mem_cgroup_lookup(unsigned short id)
-{
- /* ID 0 is unused ID */
- if (!id)
- return NULL;
- return mem_cgroup_from_id(id);
-}
-
-/*
* try_get_mem_cgroup_from_page - look up page's memcg association
* @page: the page
*
@@ -2388,7 +2380,7 @@ struct mem_cgroup *try_get_mem_cgroup_fr
ent.val = page_private(page);
id = lookup_swap_cgroup_id(ent);
rcu_read_lock();
- memcg = mem_cgroup_lookup(id);
+ memcg = mem_cgroup_from_id(id);
if (memcg && !css_tryget_online(&memcg->css))
memcg = NULL;
rcu_read_unlock();
@@ -5869,7 +5861,7 @@ void mem_cgroup_uncharge_swap(swp_entry_
id = swap_cgroup_record(entry, 0);
rcu_read_lock();
- memcg = mem_cgroup_lookup(id);
+ memcg = mem_cgroup_from_id(id);
if (memcg) {
if (!mem_cgroup_is_root(memcg))
page_counter_uncharge(&memcg->memsw, 1);
_
Patches currently in -mm which might be from vdavydov@xxxxxxxxxxxxx are
mm-hotplug-fix-concurrent-memory-hot-add-deadlock.patch
ocfs2-copy-fs-uuid-to-superblock.patch
cleancache-zap-uuid-arg-of-cleancache_init_shared_fs.patch
cleancache-forbid-overriding-cleancache_ops.patch
cleancache-remove-limit-on-the-number-of-cleancache-enabled-filesystems.patch
cleancache-remove-limit-on-the-number-of-cleancache-enabled-filesystems-fix.patch
memcg-zap-mem_cgroup_lookup.patch
mm-vmscan-fix-the-page-state-calculation-in-too_many_isolated.patch
linux-next.patch
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