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Message-ID: <20201127161828.GD840171@carbon.dhcp.thefacebook.com>
Date: Fri, 27 Nov 2020 08:18:28 -0800
From: Roman Gushchin <guro@...com>
To: Shakeel Butt <shakeelb@...gle.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Linux MM <linux-mm@...ck.org>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Kernel Team <kernel-team@...com>, <stable@...r.kernel.org>
Subject: Re: [PATCH] mm: memcg/slab: fix obj_cgroup_charge() return value
handling
On Thu, Nov 26, 2020 at 09:55:24PM -0800, Shakeel Butt wrote:
> On Thu, Nov 26, 2020 at 8:14 PM Roman Gushchin <guro@...com> wrote:
> >
> > 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.
> >
> > Fixes: 10befea91b61 ("mm: memcg/slab: use a single set of kmem_caches for all allocations")
> > Signed-off-by: Roman Gushchin <guro@...com>
> > Cc: stable@...r.kernel.org
> > ---
> > mm/slab.h | 40 ++++++++++++++++++++++++----------------
> > 1 file changed, 24 insertions(+), 16 deletions(-)
> >
> > diff --git a/mm/slab.h b/mm/slab.h
> > index 59aeb0d9f11b..5dc89d8fb05e 100644
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -257,22 +257,32 @@ static inline size_t obj_full_size(struct kmem_cache *s)
> > 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 true if the allocation should fail.
>
> IMO returning false if the allocation should fail makes this more
> clear. Otherwise the patch looks good to me.
Ok, I agree. Here is an updated version.
Thank you for looking in!
--
>From 456ce03f1c91baf5e2441dce0649e09617437fe4 Mon Sep 17 00:00:00 2001
From: Roman Gushchin <guro@...com>
Date: Thu, 26 Nov 2020 07:39:57 -0800
Subject: [PATCH v2] 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.
Fixes: 10befea91b61 ("mm: memcg/slab: use a single set of kmem_caches for all allocations")
Signed-off-by: Roman Gushchin <guro@...com>
Cc: stable@...r.kernel.org
---
mm/slab.h | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)
diff --git a/mm/slab.h b/mm/slab.h
index 59aeb0d9f11b..0698a3c0a9da 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -257,22 +257,32 @@ static inline size_t obj_full_size(struct kmem_cache *s)
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,
@@ -298,7 +308,7 @@ static inline void memcg_slab_post_alloc_hook(struct kmem_cache *s,
unsigned long off;
size_t i;
- if (!objcg)
+ if (!memcg_kmem_enabled() || !objcg)
return;
flags &= ~__GFP_ACCOUNT;
@@ -382,11 +392,11 @@ static inline void memcg_free_page_obj_cgroups(struct page *page)
{
}
-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,
@@ -494,9 +504,8 @@ static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
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;
}
@@ -515,8 +524,7 @@ static inline void slab_post_alloc_hook(struct kmem_cache *s,
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
--
2.26.2
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