The patch titled
Subject: mm, memcg: fix error return value of mem_cgroup_css_alloc()
has been added to the -mm tree. Its filename is
mm-memcg-fix-error-return-value-of-mem_cgroup_css_alloc.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-fix-error-return-value-of-mem_cgroup_css_alloc.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-fix-error-return-value-of-mem_cgroup_css_alloc.patch
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------------------------------------------------------
From: Yafang Shao <laoar.shao@xxxxxxxxx>
Subject: mm, memcg: fix error return value of mem_cgroup_css_alloc()
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 -EBUSY "Device or resource busy". That is same with
memcg_alloc_cache_id().
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': Device
or resource busy
Link: http://lkml.kernel.org/r/1586192163-20099-1-git-send-email-laoar.shao@xxxxxxxxx
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
--- a/mm/memcontrol.c~mm-memcg-fix-error-return-value-of-mem_cgroup_css_alloc
+++ a/mm/memcontrol.c
@@ -2720,6 +2720,8 @@ static int memcg_alloc_cache_id(void)
id = ida_simple_get(&memcg_cache_ida,
0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
+ if (id == -ENOSPC)
+ return -EBUSY;
if (id < 0)
return id;
@@ -4989,19 +4991,26 @@ static struct mem_cgroup *mem_cgroup_all
unsigned int size;
int node;
int __maybe_unused i;
+ long error = -ENOMEM;
size = sizeof(struct mem_cgroup);
size += nr_node_ids * sizeof(struct mem_cgroup_per_node *);
memcg = kzalloc(size, GFP_KERNEL);
if (!memcg)
- return NULL;
+ return ERR_PTR(error);
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 == -ENOSPC) {
+ error = -EBUSY;
+ goto fail;
+ }
+ if (memcg->id.id < 0) {
+ error = memcg->id.id;
goto fail;
+ }
memcg->vmstats_local = alloc_percpu(struct memcg_vmstats_percpu);
if (!memcg->vmstats_local)
@@ -5045,7 +5054,7 @@ static struct mem_cgroup *mem_cgroup_all
fail:
mem_cgroup_id_remove(memcg);
__mem_cgroup_free(memcg);
- return NULL;
+ return ERR_PTR(error);
}
static struct cgroup_subsys_state * __ref
@@ -5056,8 +5065,8 @@ mem_cgroup_css_alloc(struct cgroup_subsy
long error = -ENOMEM;
memcg = mem_cgroup_alloc();
- if (!memcg)
- return ERR_PTR(error);
+ if (IS_ERR(memcg))
+ return ERR_CAST(memcg);
WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX);
memcg->soft_limit = PAGE_COUNTER_MAX;
@@ -5107,7 +5116,7 @@ mem_cgroup_css_alloc(struct cgroup_subsy
fail:
mem_cgroup_id_remove(memcg);
mem_cgroup_free(memcg);
- return ERR_PTR(-ENOMEM);
+ return ERR_PTR(error);
}
static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
_
Patches currently in -mm which might be from laoar.shao@xxxxxxxxx are
mm-memcg-fix-error-return-value-of-mem_cgroup_css_alloc.patch
