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Thu, 13 Nov 2025 16:28:59 +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 XVg/KksHFmnkHAAAD6G6ig (envelope-from ); Thu, 13 Nov 2025 16:28:59 +0000 Message-ID: <45ea66a3-bf8b-4c12-89cd-d15ba26763fa@suse.cz> Date: Thu, 13 Nov 2025 17:28:59 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 14/16] memcg: Convert mem_cgroup_from_obj_folio() to mem_cgroup_from_obj_slab() Content-Language: en-US To: Johannes Weiner , "Matthew Wilcox (Oracle)" Cc: Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , linux-mm@kvack.org, Michal Hocko , Shakeel Butt , Muchun Song , cgroups@vger.kernel.org References: <20251113000932.1589073-1-willy@infradead.org> <20251113000932.1589073-15-willy@infradead.org> <20251113161424.GB3465062@cmpxchg.org> 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: <20251113161424.GB3465062@cmpxchg.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 7A8BC1C000E X-Stat-Signature: r7r9fswdinz3ss99e4srzt3s5cnzdps9 X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1763051341-35770 X-HE-Meta: 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 rOjpjYa8 YHxX2JVfIlvTOQhr1Ocv6S5jWV35jCxPuAc+i4K8oONURDKQau0fRr4zQSuWcaaOeLtE+/BhbLR5KSB1XjlfXQaFAKHEyema4q/bFJgtUw0LxwDfpNyu5y25fzRkPXA8TeeUs/msJgZYBHSjfdb02TvzvGAFA+Aw1uY68MTniCIC3lUQxjHe2j0rhU4vVCpBKOvEa7PR6nAx8O764Ux29TD8Gv4KsmfM9VwBYAHgvlcmf6xFFpbOKzEjL9TxaW5cZ/13gLyg6LHdeJDhDS4iMk3XdiJ41LwdgORpk7rPHLJwtYMnMIGYcPyQBQ3cYhxTNygcZISV5R7DA8Vc= 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 11/13/25 17:14, Johannes Weiner wrote: > On Thu, Nov 13, 2025 at 12:09:28AM +0000, Matthew Wilcox (Oracle) wrote: >> - /* >> - * folio_memcg_check() is used here, because in theory we can encounter >> - * a folio where the slab flag has been cleared already, but >> - * slab->obj_exts has not been freed yet >> - * folio_memcg_check() will guarantee that a proper memory >> - * cgroup pointer or NULL will be returned. >> - */ I've only noticed this comment and thought it describes something impossible to happen (maybe it was possible in the past) so seemed fine to delete it. >> - return folio_memcg_check(folio); >> + off = obj_to_index(slab->slab_cache, slab, p); >> + if (obj_exts[off].objcg) >> + return obj_cgroup_memcg(obj_exts[off].objcg); >> + >> + return NULL; >> } >> >> /* >> @@ -2637,7 +2627,7 @@ struct mem_cgroup *mem_cgroup_from_slab_obj(void *p) >> if (mem_cgroup_disabled()) >> return NULL; >> >> - return mem_cgroup_from_obj_folio(virt_to_folio(p), p); >> + return mem_cgroup_from_obj_slab(virt_to_slab(p), p); > > The name undoubtedly sucks, but there is a comment above this function > that this can be used on non-slab kernel pages as well. Didn't notice this one. > E.g. !vmap kernel stack pages -> mod_lruvec_kmem_state -> mem_cgroup_from_obj_slab > > How about: > > if ((slab = virt_to_slap(p))) > return mem_cgroup_from_obj_slab(slab, p); > return folio_memcg_check(virt_to_folio(p), p); page_memcg_check() maybe instead? we shouldn't get a tail page here, no?