From: Roman Gushchin guro@fb.com Subject: mm: memcg/slab: fix obj_cgroup_charge() return value handling

Commit 10befea91b61 ("mm: memcg/slab: use a single set of kmem_caches for all allocations") introduced a regression into the handling of the obj_cgroup_charge() return value. If a non-zero value is returned (indicating of exceeding one of memory.max limits), the allocation should fail, instead of falling back to non-accounted mode.

To make the code more readable, move memcg_slab_pre_alloc_hook() and memcg_slab_post_alloc_hook() calling conditions into bodies of these hooks.

Link: https://lkml.kernel.org/r/20201127161828.GD840171@carbon.dhcp.thefacebook.co... Fixes: 10befea91b61 ("mm: memcg/slab: use a single set of kmem_caches for all allocations") Signed-off-by: Roman Gushchin guro@fb.com Reviewed-by: Shakeel Butt shakeelb@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/slab.h | 40 ++++++++++++++++++++++++---------------- 1 file changed, 24 insertions(+), 16 deletions(-)

--- a/mm/slab.h~mm-memcg-slab-fix-obj_cgroup_charge-return-value-handling +++ a/mm/slab.h @@ -274,22 +274,32 @@ static inline size_t obj_full_size(struc return s->size + sizeof(struct obj_cgroup *); }

-static inline struct obj_cgroup *memcg_slab_pre_alloc_hook(struct kmem_cache *s, - size_t objects, - gfp_t flags) +/* + * Returns false if the allocation should fail. + */ +static inline bool memcg_slab_pre_alloc_hook(struct kmem_cache *s, + struct obj_cgroup **objcgp, + size_t objects, gfp_t flags) { struct obj_cgroup *objcg;

+ if (!memcg_kmem_enabled()) + return true; + + if (!(flags & __GFP_ACCOUNT) && !(s->flags & SLAB_ACCOUNT)) + return true; + objcg = get_obj_cgroup_from_current(); if (!objcg) - return NULL; + return true;

if (obj_cgroup_charge(objcg, flags, objects * obj_full_size(s))) { obj_cgroup_put(objcg); - return NULL; + return false; }

- return objcg; + *objcgp = objcg; + return true; }

static inline void mod_objcg_state(struct obj_cgroup *objcg, @@ -315,7 +325,7 @@ static inline void memcg_slab_post_alloc unsigned long off; size_t i;

- if (!objcg) + if (!memcg_kmem_enabled() || !objcg) return;

flags &= ~__GFP_ACCOUNT; @@ -400,11 +410,11 @@ static inline void memcg_free_page_obj_c { }

-static inline struct obj_cgroup *memcg_slab_pre_alloc_hook(struct kmem_cache *s, - size_t objects, - gfp_t flags) +static inline bool memcg_slab_pre_alloc_hook(struct kmem_cache *s, + struct obj_cgroup **objcgp, + size_t objects, gfp_t flags) { - return NULL; + return true; }

static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s, @@ -508,9 +518,8 @@ static inline struct kmem_cache *slab_pr if (should_failslab(s, flags)) return NULL;

- if (memcg_kmem_enabled() && - ((flags & __GFP_ACCOUNT) || (s->flags & SLAB_ACCOUNT))) - *objcgp = memcg_slab_pre_alloc_hook(s, size, flags); + if (!memcg_slab_pre_alloc_hook(s, objcgp, size, flags)) + return NULL;

return s; } @@ -529,8 +538,7 @@ static inline void slab_post_alloc_hook( s->flags, flags); }

- if (memcg_kmem_enabled()) - memcg_slab_post_alloc_hook(s, objcg, flags, size, p); + memcg_slab_post_alloc_hook(s, objcg, flags, size, p); }

#ifndef CONFIG_SLOB _