From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f45.google.com (mail-pa0-f45.google.com [209.85.220.45]) by kanga.kvack.org (Postfix) with ESMTP id 302306B0036 for ; Thu, 30 Jan 2014 16:39:10 -0500 (EST) Received: by mail-pa0-f45.google.com with SMTP id lf10so3651484pab.32 for ; Thu, 30 Jan 2014 13:39:09 -0800 (PST) Received: from mail-pb0-x22e.google.com (mail-pb0-x22e.google.com [2607:f8b0:400e:c01::22e]) by mx.google.com with ESMTPS id bf5si7917182pad.320.2014.01.30.13.38.58 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 30 Jan 2014 13:38:59 -0800 (PST) Received: by mail-pb0-f46.google.com with SMTP id um1so3618271pbc.19 for ; Thu, 30 Jan 2014 13:38:58 -0800 (PST) Date: Thu, 30 Jan 2014 13:38:56 -0800 (PST) From: David Rientjes Subject: Re: [PATCH] memcg: fix mutex not unlocked on memcg_create_kmem_cache fail path In-Reply-To: <20140130132939.96a25a37016a12f9a0093a90@linux-foundation.org> Message-ID: References: <1391097693-31401-1-git-send-email-vdavydov@parallels.com> <20140130130129.6f8bd7fd9da55d17a9338443@linux-foundation.org> <20140130132939.96a25a37016a12f9a0093a90@linux-foundation.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Vladimir Davydov , mhocko@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, 30 Jan 2014, Andrew Morton wrote: > > What's funnier is that tmp_name isn't required at all since > > kmem_cache_create_memcg() is just going to do a kstrdup() on it anyway, so > > you could easily just pass in the pointer to memory that has been > > allocated for s->name rather than allocating memory twice. > > We need a buffer to sprintf() into. > Yeah, it shouldn't be temporary it should be the one and only allocation. We should construct the name in memcg_create_kmem_cache() and be done with it. > diff -puN mm/memcontrol.c~mm-memcontrolc-memcg_create_kmem_cache-tweaks mm/memcontrol.c > --- a/mm/memcontrol.c~mm-memcontrolc-memcg_create_kmem_cache-tweaks > +++ a/mm/memcontrol.c > @@ -3400,24 +3400,18 @@ void mem_cgroup_destroy_cache(struct kme > static struct kmem_cache *memcg_create_kmem_cache(struct mem_cgroup *memcg, > struct kmem_cache *s) > { > - struct kmem_cache *new = NULL; > - static char *tmp_name = NULL; > - static DEFINE_MUTEX(mutex); /* protects tmp_name */ > + struct kmem_cache *new; > + char *tmp_name; > > BUG_ON(!memcg_can_account_kmem(memcg)); > > - mutex_lock(&mutex); > /* > - * kmem_cache_create_memcg duplicates the given name and > - * cgroup_name for this name requires RCU context. > - * This static temporary buffer is used to prevent from > - * pointless shortliving allocation. > + * kmem_cache_create_memcg duplicates the given name and cgroup_name() > + * for this name requires rcu_read_lock(). > */ > - if (!tmp_name) { > - tmp_name = kmalloc(PATH_MAX, GFP_KERNEL); > - if (!tmp_name) > - goto out; > - } > + tmp_name = kmalloc(PATH_MAX, GFP_KERNEL); > + if (!tmp_name) > + return NULL; > > rcu_read_lock(); > snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name, > @@ -3430,8 +3424,7 @@ static struct kmem_cache *memcg_create_k > new->allocflags |= __GFP_KMEMCG; > else > new = s; > -out: > - mutex_unlock(&mutex); > + kfree(tmp_name); > return new; > } > This is fine, but kmem_cache_create_memcg() is still just going to do a pointless kstrdup() on it which isn't necessary. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org