When I run my memcg testcase which creates lots of memcgs, I found
there're unexpected out of memory logs while there're still enough
available free memory. The error log is,
mkdir: cannot create directory 'foo.65533': Cannot allocate memory
The reason is when we try to create more than MEM_CGROUP_ID_MAX memcgs, an
-ENOMEM errno will be set by mem_cgroup_css_alloc(), but the right errno
should be -ENOSPC, as explained above the function idr_alloc().
As the errno really misled me, we should make it right. After this patch,
the error log will be,
mkdir: cannot create directory 'foo.65533': No space left on device
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
mm/memcontrol.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ca19486..9c85470 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4980,7 +4980,7 @@ static void mem_cgroup_free(struct mem_cgroup *memcg)
__mem_cgroup_free(memcg);
}
-static struct mem_cgroup *mem_cgroup_alloc(void)
+static struct mem_cgroup *mem_cgroup_alloc(long *error)
{
struct mem_cgroup *memcg;
unsigned int size;
@@ -4997,8 +4997,10 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
memcg->id.id = idr_alloc(&mem_cgroup_idr, NULL,
1, MEM_CGROUP_ID_MAX,
GFP_KERNEL);
- if (memcg->id.id < 0)
+ if (memcg->id.id < 0) {
+ *error = memcg->id.id;
goto fail;
+ }
memcg->vmstats_local = alloc_percpu(struct memcg_vmstats_percpu);
if (!memcg->vmstats_local)
@@ -5052,7 +5054,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
struct mem_cgroup *memcg;
long error = -ENOMEM;
- memcg = mem_cgroup_alloc();
+ memcg = mem_cgroup_alloc(&error);
if (!memcg)
return ERR_PTR(error);
--
1.8.3.1
