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Mon, 26 Aug 2024 19:23:11 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id wsi6DB/WzGawNAAAD6G6ig (envelope-from ); Mon, 26 Aug 2024 19:23:11 +0000 Message-ID: <6e5f3c82-a18a-4c20-858f-058f44e90ced@suse.cz> Date: Mon, 26 Aug 2024 21:23:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] slab: Warn on duplicate cache names when DEBUG_VM=y Content-Language: en-US To: Pedro Falcato , David Rientjes Cc: Christoph Lameter , Pekka Enberg , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240807090746.2146479-1-pedro.falcato@gmail.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 2139FC000A X-Stat-Signature: 4hi8xaz39ibknqneakxnqmrayjnens7a X-HE-Tag: 1724700193-379249 X-HE-Meta: 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 V9j1JdZ2 nTLct9dqcHas/Dls2kNZMjONO8sazXQtSSTJjMnniUCuhfBM1yY9SpvvQU8raFeFiwl3TZrLynqODmO3zfcakUs4dppgQEdk2ByOnfICmrbuYZgEoJXIAeXWlZVp5CkKNVZnAejDK/gHMfspDCSaooTr6kX48KTFsBHKbZ86BhqrUI+ThOKZkkHLf/+WrRaqN+/3q0rHSrMqGUzEsuurIqL53WUrKQ4qPAiVXU7/BjsvCOJE8zcf3Pg5yZanuwS/Fb7TYQZPg2tpaUxcSrY90JFyPF/zWE3+s1JTl1gPVmZuzW6itekbTvG+trSwTqd2I1fkyVAkJ3qPvZKtJCGcabAXwLm0P1bAM0Orii72M0d+AxqIRbN+1+0waoOokIL0pNEtn5Guucm5BzwhOZ6wpOk5TmYTE1W2fsPVvmI4b91VL/OE= 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: List-Subscribe: List-Unsubscribe: On 8/16/24 14:17, Pedro Falcato wrote: > On Mon, Aug 12, 2024 at 1:55 AM David Rientjes wrote: >> >> On Sun, 11 Aug 2024, Pedro Falcato wrote: >> > > > + if (kmem_cache_is_duplicate_name(name)) { >> > > > + /* Duplicate names will confuse slabtop, et al */ >> > > > + pr_warn("%s: name %s already exists as a cache\n", __func__, name); >> > > >> > > >> > > Shouldn't this be a full WARN_ON() instead of pr_warn()? I assume we'll >> > > be interested in who is adding the cache when the name already exists. >> > >> > panic_on_warn? :) >> > >> >> Would get the problem fixed up pretty fast, no? :) >> >> > Personally I don't have anything against WARN_ON, but we've seen that >> > panic_on_warn is a real thing on real systems, and DEBUG_VM is also >> > set on real prod configs (like Fedora does/used to do). I've sent out >> > one or two loose patches for problems I did find in my own testing >> > around, but there may be many more (e.g some drivers may call >> > kmem_cache_create repeatedly in some sort of callback, like 9pfs was >> > doing when mounting; this is not greppable). And I'd guess grepping >> > for cache names tends to be easy enough? >> > >> >> Can we add a dump_stack() to make this way easier instead of hiding who is >> creating the duplicate name? > > > Bah, sorry for the delay. > > I'm fully in favour of adding a dump_stack(), but it seems like hand > coding WARN_ON a bit. Oh well. After some pondering I've decided we should just go with WARN_ON and not do a hand coded workaround for hypothetical people who run CONFIG_DEBUG_VM together with panic_on_warn, so I've updated the commit in the slab tree accordingly. > If y'all agree, please squash this in (praying gmail doesn't mangle > this diff, in any case it's a trivial change): > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 1abe6a577d52..d183655e4b1b 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -111,6 +111,7 @@ static int kmem_cache_sanity_check(const char > *name, unsigned int size) > if (kmem_cache_is_duplicate_name(name)) { > /* Duplicate names will confuse slabtop, et al */ > pr_warn("%s: name %s already exists as a cache\n", > __func__, name); > + dump_stack_lvl(KERN_WARNING); > } > > WARN_ON(strchr(name, ' ')); /* It confuses parsers */