From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B677BC43334 for ; Mon, 6 Jun 2022 23:35:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 489106B0073; Mon, 6 Jun 2022 19:35:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 437DD6B0074; Mon, 6 Jun 2022 19:35:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3274F6B0075; Mon, 6 Jun 2022 19:35:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 224DB6B0073 for ; Mon, 6 Jun 2022 19:35:13 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id E6D0DF9F for ; Mon, 6 Jun 2022 23:35:12 +0000 (UTC) X-FDA: 79549419264.03.4B648AF Received: from out2.migadu.com (out2.migadu.com [188.165.223.204]) by imf22.hostedemail.com (Postfix) with ESMTP id ADF0BC0041 for ; Mon, 6 Jun 2022 23:35:08 +0000 (UTC) Date: Mon, 6 Jun 2022 16:35:05 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1654558510; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Gt4DBYgcXVKDG81Upnb2aG0Q8F7JkfTTCfOh0AVQT9U=; b=Oh/h0HqfGHO/3nl2vC7PhrBmFqKhuAGU0yX+COkhggj2alXkzkm+Lo2CQE/18WE9Rt4XaT 7elTH9cN9HLQ1lmmyi1wPVxpXhw/5FP07hvUZeQjbkRRS+4eQQ6ZaPzpSUYGK3IH8FXthp clLs7WO3Zt6ZdlyB0wIM7Rlt1MKdBaE= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Roman Gushchin To: Eric Biggers Cc: syzbot , linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Andrew Morton Subject: Re: [syzbot] WARNING in register_shrinker_prepared Message-ID: References: <000000000000db448c05e0caa5ba@google.com> <20220606122302.dc265509ca896073e98049a3@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev X-Stat-Signature: ty3zqa6mbn7pn73e3ucexwm1w9aaoqbh Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b="Oh/h0Hqf"; dmarc=pass (policy=none) header.from=linux.dev; spf=pass (imf22.hostedemail.com: domain of roman.gushchin@linux.dev designates 188.165.223.204 as permitted sender) smtp.mailfrom=roman.gushchin@linux.dev X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: ADF0BC0041 X-HE-Tag: 1654558508-738496 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 Mon, Jun 06, 2022 at 02:34:36PM -0700, Eric Biggers wrote: > On Mon, Jun 06, 2022 at 12:23:02PM -0700, Andrew Morton wrote: > > (cc Roman) > > > > On Mon, 06 Jun 2022 10:17:34 -0700 syzbot wrote: > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: 1cfd968b58a1 Add linux-next specific files for 20220603 > > > git tree: linux-next > > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=12f7b6b3f00000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=7da8386e3742814f > > > dashboard link: https://syzkaller.appspot.com/bug?extid=300d27c79fe6d4cbcc39 > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=103e5177f00000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13545057f00000 > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+300d27c79fe6d4cbcc39@syzkaller.appspotmail.com > > > > > > loop0: detected capacity change from 0 to 20 > > > ------------[ cut here ]------------ > > > WARNING: CPU: 0 PID: 3694 at mm/vmscan.c:681 register_shrinker_prepared+0x119/0x150 mm/vmscan.c:681 > > > > That's > > > > WARN_ON_ONCE(shrinker_debugfs_add(shrinker)); > > > > I assume that debugfs_create_dir() failed. Please see the NOTE: in > > that function's kerneldoc. > > > > The call to ida_alloc() can fail too. > > register_shrinker_prepared() is not allowed to fail; anything that can fail must > happen in prealloc_shrinker(). So either this new debugfs registration code > needs to be moved to prealloc_shrinker(), or errors from it need to be ignored > (which might be appropriate since it is just debugfs). I don't think we want to panic or fail to mount filesystems because of it, so I agree, ignoring is the best option.