From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 560A42594; Sun, 30 Mar 2025 02:05:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=96.67.55.147 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743300354; cv=none; b=FNL2HhpjKRo8zNHLvr3GWoOkrDY2r4RdTXIo0raqqQuF8x+noMHTUqBuX0ouv8dsOlQbpj7ciaDFbA+HAhTNIGk00o9rO2fREAVnD/DzYHGvESUhjUoPBBcIqqERI52mbAtztT/kBs1p5XqHr3EF4ap7ovfHlufs7m9Tohd2i9M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743300354; c=relaxed/simple; bh=h5eblBkeQPp3yr4CoLpcNqIK5ZT10dlT1isVczh0PZc=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Rr7AwtUzSeCzKJxVATRzthy27XrWgg/QbYcJo1YNNOZve3Vxj6kmHlnBKlZuKDKbN9SRJmy3ozYCh4XafPRx8v5dy8RE1zpnvUJMTrsZQjLCRoRN/gfb2UPy5hksKo3l/e0seTlcM6RwJOLY56eDBwMO2w2ekgwijUdsYOFgS7c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com; spf=pass smtp.mailfrom=shelob.surriel.com; arc=none smtp.client-ip=96.67.55.147 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=surriel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=shelob.surriel.com Received: from fangorn.home.surriel.com ([10.0.13.7]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.97.1) (envelope-from ) id 1tyi3K-000000001y7-0Ilg; Sat, 29 Mar 2025 22:05:34 -0400 Message-ID: <2ccb9f828ea392eb22f8deb7d9644a4575fa9ee5.camel@surriel.com> Subject: Re: [syzbot] [mm?] [fs?] BUG: sleeping function called from invalid context in folio_mc_copy From: Rik van Riel To: Luis Chamberlain , syzbot , Jan Kara , Dave Chinner Cc: brauner@kernel.org, hare@suse.de, joel.granados@kernel.org, john.g.garry@oracle.com, kees@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, willy@infradead.org Date: Sat, 29 Mar 2025 22:05:34 -0400 In-Reply-To: References: <67e57c41.050a0220.2f068f.0033.GAE@google.com> Autocrypt: addr=riel@surriel.com; prefer-encrypt=mutual; keydata=mQENBFIt3aUBCADCK0LicyCYyMa0E1lodCDUBf6G+6C5UXKG1jEYwQu49cc/gUBTTk33A eo2hjn4JinVaPF3zfZprnKMEGGv4dHvEOCPWiNhlz5RtqH3SKJllq2dpeMS9RqbMvDA36rlJIIo47 Z/nl6IA8MDhSqyqdnTY8z7LnQHqq16jAqwo7Ll9qALXz4yG1ZdSCmo80VPetBZZPw7WMjo+1hByv/ lvdFnLfiQ52tayuuC1r9x2qZ/SYWd2M4p/f5CLmvG9UcnkbYFsKWz8bwOBWKg1PQcaYHLx06sHGdY dIDaeVvkIfMFwAprSo5EFU+aes2VB2ZjugOTbkkW2aPSWTRsBhPHhV6dABEBAAG0HlJpayB2YW4gU mllbCA8cmllbEByZWRoYXQuY29tPokBHwQwAQIACQUCW5LcVgIdIAAKCRDOed6ShMTeg05SB/986o gEgdq4byrtaBQKFg5LWfd8e+h+QzLOg/T8mSS3dJzFXe5JBOfvYg7Bj47xXi9I5sM+I9Lu9+1XVb/ r2rGJrU1DwA09TnmyFtK76bgMF0sBEh1ECILYNQTEIemzNFwOWLZZlEhZFRJsZyX+mtEp/WQIygHV WjwuP69VJw+fPQvLOGn4j8W9QXuvhha7u1QJ7mYx4dLGHrZlHdwDsqpvWsW+3rsIqs1BBe5/Itz9o 6y9gLNtQzwmSDioV8KhF85VmYInslhv5tUtMEppfdTLyX4SUKh8ftNIVmH9mXyRCZclSoa6IMd635 Jq1Pj2/Lp64tOzSvN5Y9zaiCc5FucXtB9SaWsgdmFuIFJpZWwgPHJpZWxAc3VycmllbC5jb20+iQE +BBMBAgAoBQJSLd2lAhsjBQkSzAMABgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRDOed6ShMTe g4PpB/0ZivKYFt0LaB22ssWUrBoeNWCP1NY/lkq2QbPhR3agLB7ZXI97PF2z/5QD9Fuy/FD/jddPx KRTvFCtHcEzTOcFjBmf52uqgt3U40H9GM++0IM0yHusd9EzlaWsbp09vsAV2DwdqS69x9RPbvE/Ne fO5subhocH76okcF/aQiQ+oj2j6LJZGBJBVigOHg+4zyzdDgKM+jp0bvDI51KQ4XfxV593OhvkS3z 3FPx0CE7l62WhWrieHyBblqvkTYgJ6dq4bsYpqxxGJOkQ47WpEUx6onH+rImWmPJbSYGhwBzTo0Mm G1Nb1qGPG+mTrSmJjDRxrwf1zjmYqQreWVSFEt26tBpSaWsgdmFuIFJpZWwgPHJpZWxAZmIuY29tP okBPgQTAQIAKAUCW5LbiAIbIwUJEswDAAYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQznneko TE3oOUEQgAsrGxjTC1bGtZyuvyQPcXclap11Ogib6rQywGYu6/Mnkbd6hbyY3wpdyQii/cas2S44N cQj8HkGv91JLVE24/Wt0gITPCH3rLVJJDGQxprHTVDs1t1RAbsbp0XTksZPCNWDGYIBo2aHDwErhI omYQ0Xluo1WBtH/UmHgirHvclsou1Ks9jyTxiPyUKRfae7GNOFiX99+ZlB27P3t8CjtSO831Ij0Ip QrfooZ21YVlUKw0Wy6Ll8EyefyrEYSh8KTm8dQj4O7xxvdg865TLeLpho5PwDRF+/mR3qi8CdGbkE c4pYZQO8UDXUN4S+pe0aTeTqlYw8rRHWF9TnvtpcNzZw== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: riel@surriel.com On Thu, 2025-03-27 at 14:42 -0700, Luis Chamberlain wrote: > On Thu, Mar 27, 2025 at 09:26:41AM -0700, syzbot wrote: > > Hello, >=20 > Thanks, this is a known issue and we're having a hard time > reproducing [0]. >=20 > > C reproducer:=C2=A0=C2=A0 > > https://syzkaller.appspot.com/x/repro.c?x=3D152d4de4580000 >=20 > Thanks! Sadly this has not yet been able to let me reprodouce the > issue, > and so we're trying to come up with other ways to test the imminent > spin > lock + sleep on buffer_migrate_folio_norefs() path different ways > now, > including a new fstests [1] but no luck yet. The backtrace in the report seems to make the cause of the bug fairly clear, though. The function folio_mc_copy() can sleep. The function __buffer_migrate_folio() calls filemap_migrate_folio() with a spinlock held. That function eventually calls folio_mc_copy(): __might_resched+0x5d4/0x780 kernel/sched/core.c:8764 folio_mc_copy+0x13c/0x1d0 mm/util.c:742 __migrate_folio mm/migrate.c:758 [inline] filemap_migrate_folio+0xb4/0x4c0 mm/migrate.c:943 __buffer_migrate_folio+0x3ec/0x5d0 mm/migrate.c:874 move_to_new_folio+0x2ac/0xc20 mm/migrate.c:1050 migrate_folio_move mm/migrate.c:1358 [inline] migrate_folios_move mm/migrate.c:1710 [inline] The big question is how to safely release the spinlock in __buffer_migrate_folio() before calling filemap_migrate_folio() --=20 All Rights Reversed.