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 X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FCBFC433E0 for ; Sat, 13 Feb 2021 14:27:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D8DBD64DEB for ; Sat, 13 Feb 2021 14:27:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D8DBD64DEB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0C7658D00C6; Sat, 13 Feb 2021 09:27:29 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 077BC8D0060; Sat, 13 Feb 2021 09:27:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ED0A48D00C6; Sat, 13 Feb 2021 09:27:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id D3B338D0060 for ; Sat, 13 Feb 2021 09:27:28 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A1CB682499B9 for ; Sat, 13 Feb 2021 14:27:28 +0000 (UTC) X-FDA: 77813472576.03.hook37_14166e52762a Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id 864B028A4E9 for ; Sat, 13 Feb 2021 14:27:28 +0000 (UTC) X-HE-Tag: hook37_14166e52762a X-Filterd-Recvd-Size: 3685 Received: from www262.sakura.ne.jp (www262.sakura.ne.jp [202.181.97.72]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Sat, 13 Feb 2021 14:27:27 +0000 (UTC) Received: from fsav402.sakura.ne.jp (fsav402.sakura.ne.jp [133.242.250.101]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 11DEQeXB006750; Sat, 13 Feb 2021 23:26:40 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav402.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav402.sakura.ne.jp); Sat, 13 Feb 2021 23:26:40 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav402.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 11DEQeQ5006747 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sat, 13 Feb 2021 23:26:40 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: possible deadlock in start_this_handle (2) To: Jan Kara Cc: jack@suse.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tytso@mit.edu, mhocko@suse.cz, linux-mm@kvack.org, syzbot References: <000000000000563a0205bafb7970@google.com> <20210211104947.GL19070@quack2.suse.cz> From: Tetsuo Handa Message-ID: Date: Sat, 13 Feb 2021 23:26:37 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210211104947.GL19070@quack2.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 2021/02/11 19:49, Jan Kara wrote: > This stacktrace should never happen. ext4_xattr_set() starts a transaction. > That internally goes through start_this_handle() which calls: > > handle->saved_alloc_context = memalloc_nofs_save(); > > and we restore the allocation context only in stop_this_handle() when > stopping the handle. And with this fs_reclaim_acquire() should remove > __GFP_FS from the mask and not call __fs_reclaim_acquire(). Excuse me, but it seems to me that nothing prevents ext4_xattr_set_handle() from reaching ext4_xattr_inode_lookup_create() without memalloc_nofs_save() when hitting ext4_get_nojournal() path. Will you explain when ext4_get_nojournal() path is executed? ext4_xattr_set() { handle = ext4_journal_start(inode, EXT4_HT_XATTR, credits) == __ext4_journal_start() { return __ext4_journal_start_sb() { journal = EXT4_SB(sb)->s_journal; if (!journal || (EXT4_SB(sb)->s_mount_state & EXT4_FC_REPLAY)) return ext4_get_nojournal(); // Never calls memalloc_nofs_save() despite returning !IS_ERR() value. return jbd2__journal_start(journal, blocks, rsv_blocks, revoke_creds, GFP_NOFS, type, line); // Calls memalloc_nofs_save() when start_this_handle() returns 0. } } } error = ext4_xattr_set_handle(handle, inode, name_index, name, value, value_len, flags); { ext4_write_lock_xattr(inode, &no_expand); // Grabs &ei->xattr_sem error = ext4_xattr_ibody_set(handle, inode, &i, &is) { error = ext4_xattr_set_entry(i, s, handle, inode, false /* is_block */) { ret = ext4_xattr_inode_lookup_create(handle, inode, i->value, i->value_len, &new_ea_inode); // Using GFP_KERNEL based on assumption that ext4_journal_start() called memalloc_nofs_save(). } } } }