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Tue, 20 Jan 2026 14:01:23 +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 Ixu5FbOKb2kuRAAAD6G6ig (envelope-from ); Tue, 20 Jan 2026 14:01:23 +0000 Message-ID: Date: Tue, 20 Jan 2026 15:01:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slab: replace cache_from_obj() with inline checks Content-Language: en-US To: Hao Li Cc: Harry Yoo , Eric Dumazet , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev References: <20260120-b4-remove_cache_from_obj-v1-1-ace30c41eecf@suse.cz> <8bd3c3e8-9865-4467-86d5-17d891f6f21b@suse.cz> 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+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspam-User: X-Stat-Signature: cdjedsb8myqjzp75ukz7hf4y3gb8hp5u X-Rspamd-Queue-Id: B34BF140019 X-Rspamd-Server: rspam04 X-HE-Tag: 1768917685-605711 X-HE-Meta: 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 dBlaeqlA bBluglrk+7PPRkre1f+18CE6gRNbRJDnFysfD1E8pdKSe/HbfPotSn9ZzQsoPvcVQf+wt3bMM+vSK86kqsR8P6MOXHg5PuW/kgdUKZaP3mAsfkWftneCZfwH+oVYjM5gclZrqRO4IUnjEeSctbIX2zalxJAhtedNbKg4Aq6pUBa6KEMD8Woy3JR9URcO9KD0k58u0/24FefFdQtWwKl2N0QH85+RHb1OxFRbvFhSgPj0hRGG+0Kd5BkPZxJG5JX0u6MJSVCnSRWnAUuYMTdwXYoLJ1GnUzq92GvIi2vwYCeOY03hrorVb0R1coNi9YhR92tkT6a0n/9G3LJU= 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 1/20/26 14:56, Hao Li wrote: > On Tue, Jan 20, 2026 at 01:55:09PM +0100, Vlastimil Babka wrote: >> On 1/20/26 12:57, Hao Li wrote: >> >> >> @@ -6774,11 +6770,21 @@ static inline struct kmem_cache *cache_from_obj(struct kmem_cache *s, void *x) >> >> */ >> >> void kmem_cache_free(struct kmem_cache *s, void *x) >> >> { >> >> - s = cache_from_obj(s, x); >> >> - if (!s) >> >> - return; >> >> + struct slab *slab; >> >> + >> >> + slab = virt_to_slab(x); >> >> + >> >> + if (IS_ENABLED(CONFIG_SLAB_FREELIST_HARDENED) || >> >> + kmem_cache_debug_flags(s, SLAB_CONSISTENCY_CHECKS)) { >> >> + >> >> + if (unlikely(!slab || (slab->slab_cache != s))) { >> >> + warn_free_bad_obj(s, x); >> > >> > Just to make sure I'm understanding correctly, are we intentionally not >> > releasing the object x in this case? Thanks. >> >> Yes, it means something went wrong so it's better not to do anything. > > Got it, that makes sense - thanks! > >> That was true before this patch as well. > > I'm still not entirely sure I follow. I read the original code, and it seems > like it retrieved the real cache from the object and released the object into > that correct cache. Did I misunderstand something? You're right, I misread it as returning NULL, but that was only on virt_to_slab() failure. So that's a change, but I believe a proper one. But I'll mention it in the changelog and the comment. Thanks!