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Tue, 6 Jan 2026 08:00:22 +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 TKJgBBbBXGm6GwAAD6G6ig (envelope-from ); Tue, 06 Jan 2026 08:00:22 +0000 Message-ID: Date: Tue, 6 Jan 2026 09:00:21 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/mempool.c: set @elems slots to NULL once freed Content-Language: en-US To: Christoph Hellwig Cc: klourencodev@gmail.com, linux-mm@kvack.org, akpm@linux-foundation.org References: <20251223231054.16061-1-klourencodev@gmail.com> <07c4f991-ae41-456d-8e7f-287bf8676c9e@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-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 18D17180004 X-Stat-Signature: fhrfcwuit9ce8qignyf7z66jc55p1axz X-Rspam-User: X-HE-Tag: 1767686423-1801 X-HE-Meta: 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 5mH9A4ow Kp+WMwkhxsyps47PvnvtjygmpEMpF8cJ3dic14gB3pslIgdEd2coZJn15JIdadpYTva43QYYsRTOAH8bpKZN76mFSJXlvIzFpoScxct6Qb8Sz041QfPIUsAZ+uSEMac3EZ+SXOw9T9y/vVZ4XiP3XPlNRwP28aSrDpRtlJkixBAbxN9i2dnHC7B/jpun9A6aNd42zsYDecgy8zjZQCG07MWCad+YCu8Gyl79lbMZg0CGDZSIfjrViGvqOlqVaMpUgW/1QZeQ7Jn5ES5fQKwvUYHFgP5hnYJR0SPlp4L/K+nN5wfXjjnvoFmkahw== 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 1/6/26 07:22, Christoph Hellwig wrote: > On Mon, Jan 05, 2026 at 05:46:47PM +0100, Vlastimil Babka wrote: >> On 12/24/25 00:10, klourencodev@gmail.com wrote: >> > From: Kevin Lourenco >> > >> > This is documented in the function comment as "...and sets their >> > slots in @elems to NULL.", but it was not followed. >> > >> > We need to follow the NULL assignment, because elements newly returned >> > to the pool must not be touched under any circumstances by the user. >> >> Well alternatively we could update the comment if no user needs to rely on >> this. Since it was modeled after __alloc_pages_bulk()/release_pages() and >> release_pages() doesn't do this, we could also avoid it for perf reasons. >> Christoph, what do you think? > > Not sure. I hate the magic null skipping behavior in > __alloc_pages_bulk()/release_pages(), but given that we try to stay > compatible it might be best to do this. Well but release_pages() is null skipping but not NULL creating?