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 -ENOSPC "No space left on device", which is an appropriate errno for userspace's failed mkdir. 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" [akpm@xxxxxxxxxxxxxxxxxxxx: s/EBUSY/ENOSPC/, per Michal] [akpm@xxxxxxxxxxxxxxxxxxxx: s/EBUSY/ENOSPC/, per Michal] Link: http://lkml.kernel.org/r/20200407063621.GA18914@xxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/1586192163-20099-1-git-send-email-laoar.shao@xxxxxxxxx Fixes: 73f576c04b94 ("mm: memcontrol: fix cgroup creation failure after many small jobs") Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxxxx> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) --- a/mm/memcontrol.c~mm-memcg-fix-error-return-value-of-mem_cgroup_css_alloc +++ a/mm/memcontrol.c @@ -4990,19 +4990,22 @@ 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 < 0) { + error = memcg->id.id; goto fail; + } memcg->vmstats_local = alloc_percpu(struct memcg_vmstats_percpu); if (!memcg->vmstats_local) @@ -5046,7 +5049,7 @@ 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 @@ -5057,8 +5060,8 @@ 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; @@ -5108,7 +5111,7 @@ 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) _
