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Fri, 24 Jan 2025 16:28:11 +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 3HFyKJu/k2f8EQAAD6G6ig (envelope-from ); Fri, 24 Jan 2025 16:28:11 +0000 Message-ID: <2b2e6e04-b91d-4d9d-9cf9-5c690abe6746@suse.cz> Date: Fri, 24 Jan 2025 17:28:11 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v6 0/6] bpf, mm: Introduce try_alloc_pages() Content-Language: en-US To: Alexei Starovoitov Cc: Matthew Wilcox , bpf , Andrii Nakryiko , Kumar Kartikeya Dwivedi , Andrew Morton , Peter Zijlstra , Sebastian Sewior , Steven Rostedt , Hou Tao , Johannes Weiner , Shakeel Butt , Michal Hocko , Thomas Gleixner , Jann Horn , Tejun Heo , linux-mm , Kernel Team , Marco Elver , Andrey Konovalov , Oscar Salvador References: <20250124035655.78899-1-alexei.starovoitov@gmail.com> 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+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 94A40140018 X-Rspamd-Server: rspam10 X-Stat-Signature: tsc9cptujhdasdu9q9wusuk4jknn768z X-HE-Tag: 1737736093-980610 X-HE-Meta: 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 g5NU2kh7 fc0V6sIx5kSHqUwzVBnyCEghv+RaH6cm5ZUrifucF3KRgXUHiAxIhhuy344oYaKishvCJKwy/C7herw0wc9DQbw5UgtMooTGuNv/dmZ38l3BB5ubm5uPs4NymMLcJMNovWofgTlORCi9SxEk2/ewXSsYl77cyXiiRGqBRIFfsZfe9d5Oamrg/sGJtb+6AKYU7CwFWlC7vtPzLWA2zPYmfiIXGcWiFp0AAA0HForun51OVT+JIK6jenN5bt9E7Xelo4r1BKrg9ZCnwB8Pd4583b38QN1LYq1Oe7JMT5UDMFobOb4ksznEIxhzRJRjw4Vd13VYUVJSYWAE0KL7K8ikmAgxzYtoYa8U+1O8YRYzg0syNay5mUYXgV004YdsHgH9rkFvq5JRfo0IXMpKxmg4aPJSjUmdhZI3Rcln9xy7UK5pqSBI= 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 1/24/25 17:19, Alexei Starovoitov wrote: > On Fri, Jan 24, 2025 at 6:19 AM Vlastimil Babka wrote: >> >> On 1/24/25 15:16, Matthew Wilcox wrote: >> > On Thu, Jan 23, 2025 at 07:56:49PM -0800, Alexei Starovoitov wrote: >> >> - Considered using __GFP_COMP in try_alloc_pages to simplify >> >> free_pages_nolock a bit, but then decided to make it work >> >> for all types of pages, since free_pages_nolock() is used by >> >> stackdepot and currently it's using non-compound order 2. >> >> I felt it's best to leave it as-is and make free_pages_nolock() >> >> support all pages. >> > >> > We're trying to eliminate non-use of __GFP_COMP. Because people don't >> > use __GFP_COMP, there's a security check that we can't turn on. Would >> > you reconsider this change you made? >> >> This means changing stackdepot to use __GFP_COMP. Which would be a good >> thing on its own. But if you consider if off-topic to your series, I can >> look at it. > > Ohh. I wasn't aware of that. > I can certainly add __GFP_COMP to try_alloc_pages() and Yeah IIRC I suggested that previously. > will check stackdepot too. Great, thanks. > I spotted this line: > VM_BUG_ON_PAGE(compound && compound_order(page) != order, page); > that line alone was a good enough reason to use __GFP_COMP, > but since it's debug only I could only guess where the future lies. > > Should it be something like: > > if (WARN_ON(compound && compound_order(page) != order)) > order = compound_order(page); > > since proceeding with the wrong order is certain to crash. > ? That's the common question, should we be paranoid and add overhead to fast paths in production. Here we do only for DEBUG_VM, which is meant for easier debugging during development of new code. I think it's not worth adding this overhead in normal configs, as the (increasing) majority of order > 0 parameters should come here from compound_order() anyway (i.e. put_folio()) As said we're trying to eliminate the other cases so we don't need to cater for them more.