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Tue, 30 Apr 2024 05:31:25 +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 3xKGDi2CMGb/DQAAD6G6ig (envelope-from ); Tue, 30 Apr 2024 05:31:25 +0000 Message-ID: <1fb5b8f3-d8c7-4350-888a-ad8f4d54bc66@suse.cz> Date: Tue, 30 Apr 2024 07:31:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm,page_owner: don't remove GFP flags in add_stack_record_to_list To: Dave Chinner Cc: Christoph Hellwig , akpm@linux-foundation.org, osalvador@suse.de, elver@google.com, andreyknvl@gmail.com, linux-mm@kvack.org, djwong@kernel.org, linux-xfs@vger.kernel.org References: <20240429054706.1543980-1-hch@lst.de> <3e486c7f-57d4-4a36-a949-0cf19f10bf4f@suse.cz> Content-Language: en-US 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: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 37F7914000E X-Stat-Signature: bpt1p3abb9snpzthryrm7ocdspot3ax6 X-Rspam-User: X-HE-Tag: 1714455086-248566 X-HE-Meta: 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 9ihojFaI D32Pg0wKabjMIACU= 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 4/30/24 1:49 AM, Dave Chinner wrote: > On Mon, Apr 29, 2024 at 09:59:43AM +0200, Vlastimil Babka wrote: >> On 4/29/24 7:47 AM, Christoph Hellwig wrote: >> > This loses flags like GFP_NOFS and GFP_NOIO that are important to avoid >> > deadlocks as well as GFP_NOLOCKDEP that otherwise generates lockdep false >> > positives. >> >> GFP_NOFS and GFP_NOIO translate to GFP_KERNEL without __GFP_FS/__GFP_IO so I >> don't see how this patch would have helped with those. >> __GFP_NOLOCKDEP is likely the actual issue and stackdepot solved it like this: >> >> https://lore.kernel.org/linux-xfs/20240418141133.22950-1-ryabinin.a.a@gmail.com/ >> >> So we could just do the same here. > > Yes, it is __GFP_NOLOCKDEP that is the issue here, but > cargo-cult-copying of that stackdepot fix is just whack-a-mole bug > fixing without addressing the technical debt that got us here in the > first place. Has anyone else bothered to look to see if kmemleak has > the same problem? Looks like you did :) > If anyone bothered to do an audit, they would see that > gfp_kmemleak_mask() handles the reclaim context masks correctly. > Further, it adds NOWARN, NOMEMALLOC and > NORETRY, which means the debug code is silent when it fails, it > doesn't deplete emergency reserves and doesn't bog down retrying > forever when there are sustained low memory situations. So we do have NOWARN here. __GFP_RETRY_MAYFAIL might have been slightly better than __GFP_NOWARN wrt "not retrying forever" but also not giving up too soon. If we want to be really careful about reserves, it's a question whether to keep the | GFP_ATOMIC which translates to leaving __GFP_HIGH. OTOH if we don't keep it, these allocations might fail too easily from an atomic context and we could miss the debugging data. > This also points out that the page-owner/stackdepot code that strips > GFP_ZONEMASK is completely redundant. Doing: > > gfp_flags &= GFP_KERNEL|GFP_ATOMIC|__GFP_NOLOCKDEP; > > strips everything but __GFP_RECLAIM, __GFP_FS, __GFP_IO, > __GFP_HIGH and __GFP_NOLOCKDEP. This already strips the zonemask > info, so there's no need to do it explicitly. True. > IOWs, the right way to fix this set of problems is to lift > gfp_kmemleak_mask() to include/linux/gfp.h and then use it across > all these nested allocations that occur behind the public > memory allocation API. Agree. But arguably these quick fixes adding __GFP_NOLOCKDEP were appropriate for the late rc phase we're in. > I've got a patchset under test at the moment that does this.... Great! Thanks. > -Dave.