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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91E5EC43334 for ; Fri, 24 Jun 2022 12:51:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231847AbiFXMvg (ORCPT ); Fri, 24 Jun 2022 08:51:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59710 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231747AbiFXMvc (ORCPT ); Fri, 24 Jun 2022 08:51:32 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 401434ECE7 for ; Fri, 24 Jun 2022 05:51:31 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 5D73121A31; Fri, 24 Jun 2022 12:51:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1656075082; h=from:from:reply-to: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=klkWcB8YXFDUWta4RZ2XPvk2TPvFr+O/8NLNr7voBg4=; b=sPgrxGlZUqh/LrvRfi2/0XI9ZtH1G/3cNK9h/Mi7NUGM26tDny1b9LsE3kOHeAVNB8S5v7 e9KuQRVPCYHIIJoJPhyWFPDWjbvBPhKH2j4spPeqB+Zf8AKRw68H6gGtlYad7oJKwTiCa5 1BtBkvu3mln+YBjYZazR/mXOXY9bM/4= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1656075082; h=from:from:reply-to: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=klkWcB8YXFDUWta4RZ2XPvk2TPvFr+O/8NLNr7voBg4=; b=W1CLDjtnEGOgM+COJfSMt9pObXSeuqHp7JJNrWAVuK0/k4TVls2V+/EsnNM7nootYiDntq eqrumZo2OLTvpYAA== Received: from quack3.suse.cz (unknown [10.100.224.230]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 921762C220; Fri, 24 Jun 2022 12:51:21 +0000 (UTC) Received: by quack3.suse.cz (Postfix, from userid 1000) id F26C9A062D; Fri, 24 Jun 2022 14:51:17 +0200 (CEST) Date: Fri, 24 Jun 2022 14:51:17 +0200 From: Jan Kara To: Zhang Yi Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, yukuai3@huawei.com Subject: Re: [PATCH] ext4: silence the warning when evicting inode with dioread_nolock Message-ID: <20220624125117.bi5o4ovuhhtgs44x@quack3.lan> References: <20220624070404.763603-1-yi.zhang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220624070404.763603-1-yi.zhang@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Fri 24-06-22 15:04:04, Zhang Yi wrote: > When evicting an inode with default dioread_nolock, it could be raced by > the unwritten extents converting kworker after writeback some new > allocated dirty blocks. It convert unwritten extents to written, the > extents could be merged to upper level and free extent blocks, so it > could mark the inode dirty again even this inode has been marked > I_FREEING. But the inode->i_io_list check and warning in > ext4_evict_inode() missing this corner case. Fortunately, > ext4_evict_inode() will wait all extents converting finished before this > check, so it will not lead to inode use-after-free problem, so every > thing is OK besides this warning, let the WARN_ON_ONCE know the > dioread_nolock case to silence this warning is fine. > > ====== > WARNING: CPU: 7 PID: 1092 at fs/ext4/inode.c:227 > ext4_evict_inode+0x875/0xc60 > ... > RIP: 0010:ext4_evict_inode+0x875/0xc60 > ... > Call Trace: > > evict+0x11c/0x2b0 > iput+0x236/0x3a0 > do_unlinkat+0x1b4/0x490 > __x64_sys_unlinkat+0x4c/0xb0 > do_syscall_64+0x3b/0x90 > entry_SYSCALL_64_after_hwframe+0x46/0xb0 > RIP: 0033:0x7fa933c1115b > ====== > > rm kworker > ext4_end_io_end() > vfs_unlink() > ext4_unlink() > ext4_convert_unwritten_io_end_vec() > ext4_convert_unwritten_extents() > ext4_map_blocks() > ext4_ext_map_blocks() > ext4_ext_try_to_merge_up() > __mark_inode_dirty() > check !I_FREEING > locked_inode_to_wb_and_lock_list() > iput() > iput_final() > evict() > ext4_evict_inode() > truncate_inode_pages_final() //wait release io_end > inode_io_list_move_locked() > ext4_release_io_end() > trigger WARN_ON_ONCE() > > Fixes: ceff86fddae8 ("ext4: Avoid freeing inodes on dirty list") > Signed-off-by: Zhang Yi Good catch! So for the i_nlink == 0 case below, I'd just remove the WARN_ON_ONCE altogether. It isn't very useful after your change anyway. But probably we should add: WARN_ON_ONCE(!list_empty(&inode->i_io_list)); to the no_delete: case of ext4_evict_inode()? Race like you mention above does not seem possible for that case but seeing the complicated interactions I'd rather have the assertion in place. Honza > --- > fs/ext4/inode.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 3dce7d058985..3b64d72416b7 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -220,11 +220,14 @@ void ext4_evict_inode(struct inode *inode) > > /* > * For inodes with journalled data, transaction commit could have > - * dirtied the inode. Flush worker is ignoring it because of I_FREEING > - * flag but we still need to remove the inode from the writeback lists. > + * dirtied the inode. And for inodes with dioread_nolock, unwritten > + * extents converting worker could merged extents and also have dirtied > + * the inode. Flush worker is ignoring it because of I_FREEING flag but > + * we still need to remove the inode from the writeback lists. > */ > if (!list_empty_careful(&inode->i_io_list)) { > - WARN_ON_ONCE(!ext4_should_journal_data(inode)); > + WARN_ON_ONCE(!ext4_should_journal_data(inode) && > + !ext4_should_dioread_nolock(inode)); > inode_io_list_del(inode); > } > > -- > 2.31.1 > -- Jan Kara SUSE Labs, CR