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Mon, 26 Jan 2026 09:10:31 +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 yEmHJocvd2ltSAAAD6G6ig (envelope-from ); Mon, 26 Jan 2026 09:10:31 +0000 Message-ID: <7ff42564-9c21-41b4-88fa-9733387fe4f4@suse.cz> Date: Mon, 26 Jan 2026 10:10:31 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: avoid allocating slabobj_ext array from its own slab Content-Language: en-US To: Harry Yoo Cc: akpm@linux-foundation.org, linux-mm@kvack.org, cl@gentwo.org, rientjes@google.com, surenb@google.com, hao.li@linux.dev, kernel test robot , stable@vger.kernel.org References: <20260124104614.9739-1-harry.yoo@oracle.com> <2b116198-b27a-4b20-90b2-951343f9fff1@suse.cz> <55ab1a9b-1d7a-4e7e-b6bc-ee327197dc4b@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-Stat-Signature: b1zpq8yd3ordj1m36beff9im7ciy6i93 X-Rspamd-Queue-Id: 91B4E1C0007 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1769418633-299095 X-HE-Meta: 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 CZgUvFAX mCm7PBO0ctWlW/0DumlZnboK+kIMn6siyqYaMZ88WVCmGmZlnLmsWjNgexi3qnNLETt2wGMrN90aEGvZVjIh2oAp0JIiIhebg9pxKaIIn+xwhVx8fIFT8KFIfaQg9Ts4gvmFFi5x8PgwRNqzzfTSbgrG3KjZQ5Sbk66/mBTcAbyymKeSy2kGbLMlcWjB9/3K1Lchv8S0OLgVD6CHRpQcK1m5InN8Co4YLc11bvB2ir/1Lpu2b7bQHq67IoNbgGxGljwX9FbyXNNlCmbpjUGX7qGhoNV3taYlwIMuARfKF9QudGh/SQkP265pVmUvVSu1+EqBa93Pygnf9rcY= 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 1/26/26 09:57, Harry Yoo wrote: >> >> Maybe start with something like "We can't simply compare s with >> obj_exts_cache, because..." >> >> > * is selected by the caller address. Since caller address may differ >> > * between kmalloc_slab() and actual allocation, bump size when both >> > * are normal kmalloc caches of same size. >> >> As we don't test the other for normal kmalloc(), anymore this now reads as >> if we forgot to. > > Ok, something like this: > > "We can't simply compare s with obj_exts_cache, because random kmalloc > caches have multiple caches per size, selected by caller address. > Since caller address may differ between kmalloc_slab() and actual > allocation, bump size when sizes are equal." LGTM!