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Thu, 6 Nov 2025 14:57:13 +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 IIQFKEm3DGlyYQAAD6G6ig (envelope-from ); Thu, 06 Nov 2025 14:57:13 +0000 Message-ID: Date: Thu, 6 Nov 2025 15:57:13 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/9] mempool: add mempool_{alloc,free}_bulk Content-Language: en-US To: Christoph Hellwig Cc: Jens Axboe , Eric Biggers , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-mm@kvack.org References: <20251031093517.1603379-1-hch@lst.de> <20251031093517.1603379-4-hch@lst.de> <1fff522d-1987-4dcc-a6a2-4406a22d3ec2@suse.cz> <20251106141306.GA12043@lst.de> <20251106144846.GA15119@lst.de> 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: <20251106144846.GA15119@lst.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 4AEBB1A000D X-Stat-Signature: usf975tdy6rrr9fo6rqbstefkj3aetk3 X-HE-Tag: 1762441035-9671 X-HE-Meta: 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 VSEEzQYg FA9CEoKjzhbgs4RQpjD8Ii74kkqF3BkcPuwDLRsvtiOAo1eaR/g785swdR51up/WOGxszh3vSAaz/DswbyCEwjpW7/VAKJqPCa2B/g29iZTSgUkZ/pxHw26MNLl6VvUZ+jt/d03geDfd3nMp0b/041oBJwQ0RgrVzDRTQevECLopdA4I8nMGn1wAHdfSv8TjOx2fkihAGLNY+XXbJgy1UdZgSR3H9PXaxFkNkUT8iUd867PD8mJm6QYWPHONHUCWDBAlLlx9himzGRGvUVM5pnbrlVcyj2Nj1N8zO+JpRc56IlXqT/yZAcT+2js28LKVNlWu/e2yq7hGreoc= 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 11/6/25 15:48, Christoph Hellwig wrote: > On Thu, Nov 06, 2025 at 03:27:35PM +0100, Vlastimil Babka wrote: >> >> Would it be enough to do this failure injection attempt once and not in >> >> every iteration? >> > >> > Well, that would only test failure handling for the first element. Or >> > you mean don't call it again if called once? >> >> I mean since this is (due to the semantics of mempools) not really causing a >> failure to the caller (unlike the typical failure injection usage), but >> forcing preallocated objecs use, I'm not sure we get much benefit (in terms >> of testing caller's error paths) from the fine grained selection of the >> first element where we inject fail, and failing immediately or never should >> be sufficient. > > I guess. OTOH testing multiple failures could be useful? Maybe, guess I don't care that much, as long as it's not causing overhead on every iteration when disabled, which it shouldn't. >> > Yes, this looks like broken copy and paste. The again I'm not even >> > sure who calls into mempool without __GFP_DIRECT_RECLAIM reset, as >> > that's kinda pointless. >> >> Hm yeah would have to be some special case where something limits how many >> such outstanding allocations can there be, otherwise it's just a cache to >> make success more likely but not guaranteed. > > I think the only reason mempool_alloc even allows !__GFP_DIRECT_RECLAIM > is to avoid special casing that in callers that have a non-constant > gfp mask. So maybe the best thing would be to never actually go to > the pool for them and just give up if alloc_fn fails? Yeah, but I guess we could keep trying the pool for the single allocation case as that's simple enough, just not for the bulk. >> >> > * This function only sleeps if the free_fn callback sleeps. >> >> >> >> This part now only applies to mempool_free() ? >> > >> > Both mempool_free and mempool_free_bulk. >> >> But mempool_free_bulk() doesn't use the callback, it's up to the caller to >> free anything the mempool didn't use for its refill. > > You're right. So mempool_free_bulk itself will indeed never sleep and > I'll fix that up.