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Content-Language: en-US To: Hyesoo Yu Cc: janghyuck.kim@samsung.com, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20250205004615.1253389-1-hyesoo.yu@samsung.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: <20250205004615.1253389-1-hyesoo.yu@samsung.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Level: X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCPT_COUNT_SEVEN(0.00)[11]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; TAGGED_RCPT(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[samsung.com,linux.com,kernel.org,google.com,lge.com,linux-foundation.org,linux.dev,gmail.com,kvack.org,vger.kernel.org]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.cz:mid,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -2.80 X-Spam-Flag: NO On 2/5/25 01:46, Hyesoo Yu wrote: > If a slab object is corrupted or an error occurs in its internal > value, continuing after restoration may cause other side effects. > At this point, it is difficult to debug because the problem occurred > in the past. It is better to use WARN() instead of pr_err to catch > errors at the point of issue because WARN() could trigger panic for > system debugging when panic_on_warn is enabled. WARN() should be > called prior to fixing the value because when a panic is triggered by WARN(), > it allows us to check corrupted data. > > Changes in v2: > - Replace direct calling with BUG_ON with the use of WARN in slab_fix. > > Signed-off-by: Hyesoo Yu Hi and thanks for the patch, I wonder if it would be better not to change slab_fix() but rather slab_err() and object_err(). It wouldn't then require to rearrange the fixup code. Also I think some error reporting paths don't go through slab_fix() and we still would like them to become a WARN too. Basically it would mean the last line in slab_err() would be a WARN and we'd drop the dump_stack() as that's redundant. Same in object_err() (no dump_stack() there). It would be a bit noisier as a result, but hopefully acceptable. The slab specific debugging info would still be printed before the WARN hits (and potentially results in a panic) so anyone investigating the crash dump would have that information. Hm but I see some places print stuff after slab_err(). slab_pad_check() and list_slab_objects(). We could create slab_err_start() and slab_err_end() for those, and slab_err() would just call both at once. > --- > mm/slub.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 1f50129dcfb3..ea956cb4b8be 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -1043,7 +1043,7 @@ static void slab_fix(struct kmem_cache *s, char *fmt, ...) > va_start(args, fmt); > vaf.fmt = fmt; > vaf.va = &args; > - pr_err("FIX %s: %pV\n", s->name, &vaf); > + WARN(1, "FIX %s: %pV\n", s->name, &vaf); > va_end(args); > } > > @@ -1106,8 +1106,8 @@ static bool freelist_corrupted(struct kmem_cache *s, struct slab *slab, > if ((s->flags & SLAB_CONSISTENCY_CHECKS) && > !check_valid_pointer(s, slab, nextfree) && freelist) { > object_err(s, slab, *freelist, "Freechain corrupt"); > - *freelist = NULL; > slab_fix(s, "Isolate corrupted freechain"); > + *freelist = NULL; > return true; > } > > @@ -1445,9 +1445,9 @@ static int on_freelist(struct kmem_cache *s, struct slab *slab, void *search) > set_freepointer(s, object, NULL); > } else { > slab_err(s, slab, "Freepointer corrupt"); > + slab_fix(s, "Freelist cleared"); > slab->freelist = NULL; > slab->inuse = slab->objects; > - slab_fix(s, "Freelist cleared"); > return 0; > } > break; > @@ -1464,14 +1464,14 @@ static int on_freelist(struct kmem_cache *s, struct slab *slab, void *search) > if (slab->objects != max_objects) { > slab_err(s, slab, "Wrong number of objects. Found %d but should be %d", > slab->objects, max_objects); > - slab->objects = max_objects; > slab_fix(s, "Number of objects adjusted"); > + slab->objects = max_objects; > } > if (slab->inuse != slab->objects - nr) { > slab_err(s, slab, "Wrong object count. Counter is %d but counted were %d", > slab->inuse, slab->objects - nr); > - slab->inuse = slab->objects - nr; > slab_fix(s, "Object count adjusted"); > + slab->inuse = slab->objects - nr; > } > return search == NULL; > }