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Sat, 20 May 2023 22:14:54 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <48a6a627-183d-6331-0d8d-ae4b1d4b0101@I-love.SAKURA.ne.jp> Date: Sat, 20 May 2023 22:14:54 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH] lib/stackdepot: stackdepot: don't use __GFP_KSWAPD_RECLAIM from __stack_depot_save() if atomic context Content-Language: en-US From: Tetsuo Handa To: syzbot , syzkaller-bugs@googlegroups.com, Mel Gorman , "Huang, Ying" , Vlastimil Babka , Andrew Morton , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Andrey Ryabinin Cc: kasan-dev , linux-mm References: <000000000000cef3a005fc1bcc80@google.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 027CC10000E X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: bxxeueawrpogpbkoko9fprq4eo8uzjqu X-HE-Tag: 1684588518-353643 X-HE-Meta: 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 wwc8se0i 4LglRm0gf6+dlsH7EmEz/uA7ZlITFBowcMbeZAiOkb/TM/oxoAO0E7MGJCYoX5g98G+UvDcqExOAsoQ/dQiwm62asoF3TDjNT3MeNngmr1OLx4Tv/fwE8JQHrXTS6ttiJkwIalzHusn9bTSjnscWzMH/KNI7/SeIN7jJac0/8DKJIqbgHGgmwmslLJbHbwIRyij+EzgjSTkdgZBXImX0L+U2Xifj1czUcsj9mQ/S4H+NQvfxvtE5oHZpJ0rgtrNDCEQ7LYR1TGjLUNZ9JLWyWS+BqZLBwvQrvnDzqf7Wje/UuvNrnzcFB741I9ViIb2lRKHt6IEHeAFg3ck4hB2fPsdGbpX4JxCB4rnuKihI1QcqiHITn0FNJO/wJHp6bcG89+Pse18BqhalZpu107OXpIKvU1uRMWMLG/rs1LQCJBQNdtao= 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: On 2023/05/20 20:33, Tetsuo Handa wrote: > @@ -405,7 +405,10 @@ depot_stack_handle_t __stack_depot_save(unsigned long *entries, > * contexts and I/O. > */ > alloc_flags &= ~GFP_ZONEMASK; > - alloc_flags &= (GFP_ATOMIC | GFP_KERNEL); > + if (!(alloc_flags & __GFP_DIRECT_RECLAIM)) > + alloc_flags &= __GFP_HIGH; > + else > + alloc_flags &= GFP_KERNEL; > alloc_flags |= __GFP_NOWARN; Well, comparing with a report which reached __stack_depot_save() via fill_pool() ( https://syzkaller.appspot.com/bug?extid=358bb3e221c762a1adbb ), I feel that above lines might be bogus. Maybe we want to enable __GFP_HIGH even if alloc_flags == GFP_NOWAIT because fill_pool() uses __GFPHIGH | __GFP_NOWARN regardless of the caller's context. Then, these lines could be simplified like below. if (!(alloc_flags & __GFP_DIRECT_RECLAIM)) alloc_flags = __GFP_HIGH | __GFP_NOWARN; else alloc_flags = (alloc_flags & GFP_KERNEL) | __GFP_NOWARN; How is the importance of memory allocation in __stack_depot_save() ? If allocation failure is welcome, maybe we should not trigger OOM killer by clearing __GFP_NORETRY when alloc_flags contained __GFP_FS ... > page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER); > if (page)