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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> 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-Rspamd-Queue-Id: C042CA000D X-Rspam-User: X-Stat-Signature: 8tkt6xsmohdzcqxzp88goise3gyaxpuz X-Rspamd-Server: rspam03 X-HE-Tag: 1711016316-514692 X-HE-Meta: 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 QCwUo3IC li6y09VmiqXagopvScgF0LX4e3irslwaKTFKyLzjTMoIUWssmpGuHOmDDYw20zFIMlnV6OQwnWs0mnCxFSuJNeeLsd83MzDzPPbSZ 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 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