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Thu, 21 Mar 2024 10:18:34 +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 011+D3oJ/GUBGwAAD6G6ig (envelope-from ); Thu, 21 Mar 2024 10:18:34 +0000 Date: Thu, 21 Mar 2024 11:20:00 +0100 From: Oscar Salvador To: Muchun Song Cc: syzbot , David Hildenbrand , Matthew Wilcox , Andrew Morton , LKML , Linux-MM , syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] kernel BUG in const_folio_flags Message-ID: References: <0000000000006cfe98061423cde7@google.com> <812E97E8-668F-414D-9480-1D284834A034@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <812E97E8-668F-414D-9480-1D284834A034@linux.dev> X-Spam-Level: Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=T2QWm8qW; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=rzqqpvn+ X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-3.49 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BAYES_HAM(-1.48)[91.54%]; TAGGED_RCPT(0.00)[3b9148f91b7869120e81]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_LONG(-1.00)[-1.000]; DWL_DNSWL_MED(-2.00)[suse.de:dkim]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+]; MX_GOOD(-0.01)[]; RCPT_COUNT_SEVEN(0.00)[8]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; NEURAL_HAM_SHORT(-0.20)[-1.000]; RCVD_TLS_ALL(0.00)[]; SUSPICIOUS_RECIPS(1.50)[]; SUBJECT_HAS_QUESTION(0.00)[] X-Spam-Score: -3.49 X-Rspamd-Queue-Id: BF3065CC22 X-Spam-Flag: NO On Thu, Mar 21, 2024 at 05:49:49PM +0800, Muchun Song wrote: > There are some more page dumping information from console: > > [ 61.367144][ T42] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888028132880 pfn:0x28130 > [ 61.371430][ T42] flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff) > [ 61.374455][ T42] page_type: 0xffffffff() > [ 61.376096][ T42] raw: 00fff80000000000 ffff888015ecd540 dead000000000100 0000000000000000 > [ 61.379994][ T42] raw: ffff888028132880 0000000000190000 00000000ffffffff 0000000000000000 > > Alright, the page is freed (with a refcount of 0). Yes, basically the page changed betwen folio_test_large() (returned true for PG_Head) and the call to const_folio_flags() (which now returned false for PG_Head). As David pointed out, Willy is working on making PageHutelb more robust [1]. [1] https://lore.kernel.org/linux-mm/20240314012506.1600378-1-willy@infradead.org/ -- Oscar Salvador SUSE Labs