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Wed, 3 Nov 2021 07:23:57 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id I5R1GQ05gmHFOQAAMHmgww (envelope-from ); Wed, 03 Nov 2021 07:23:57 +0000 Message-ID: Date: Wed, 3 Nov 2021 08:23:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.1 Subject: Re: [PATCH] mm/slab_common: use WARN() if cache still has objects on destroy Content-Language: en-US To: Marco Elver , Andrew Morton Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dmitry Vyukov , Alexander Potapenko , kasan-dev@googlegroups.com, Ingo Molnar References: <20211102170733.648216-1-elver@google.com> From: Vlastimil Babka In-Reply-To: <20211102170733.648216-1-elver@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 987BB9000380 X-Stat-Signature: fh79pj364bapztaj8o43x8usgduxkr4c Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=YPpVRsyE; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=Ss3QaDDF; spf=pass (imf23.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Rspamd-Server: rspam02 X-HE-Tag: 1635924227-968074 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11/2/21 18:07, Marco Elver wrote: > Calling kmem_cache_destroy() while the cache still has objects allocated > is a kernel bug, and will usually result in the entire cache being > leaked. While the message in kmem_cache_destroy() resembles a warning, > it is currently not implemented using a real WARN(). > > This is problematic for infrastructure testing the kernel, all of which > rely on the specific format of WARN()s to pick up on bugs. > > Some 13 years ago this used to be a simple WARN_ON() in slub, but > d629d8195793 ("slub: improve kmem_cache_destroy() error message") > changed it into an open-coded warning to avoid confusion with a bug in > slub itself. > > Instead, turn the open-coded warning into a real WARN() with the message > preserved, so that test systems can actually identify these issues, and > we get all the other benefits of using a normal WARN(). The warning > message is extended with "when called from " to make it even > clearer where the fault lies. > > For most configurations this is only a cosmetic change, however, note > that WARN() here will now also respect panic_on_warn. > > Signed-off-by: Marco Elver Makes sense. Reviewed-by: Vlastimil Babka > --- > mm/slab_common.c | 11 +++-------- > 1 file changed, 3 insertions(+), 8 deletions(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index ec2bb0beed75..0155a3042203 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -497,8 +497,6 @@ void slab_kmem_cache_release(struct kmem_cache *s) > > void kmem_cache_destroy(struct kmem_cache *s) > { > - int err; > - > if (unlikely(!s)) > return; > > @@ -509,12 +507,9 @@ void kmem_cache_destroy(struct kmem_cache *s) > if (s->refcount) > goto out_unlock; > > - err = shutdown_cache(s); > - if (err) { > - pr_err("%s %s: Slab cache still has objects\n", > - __func__, s->name); > - dump_stack(); > - } > + WARN(shutdown_cache(s), > + "%s %s: Slab cache still has objects when called from %pS", > + __func__, s->name, (void *)_RET_IP_); > out_unlock: > mutex_unlock(&slab_mutex); > cpus_read_unlock(); >