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 D8015C433EF for ; Mon, 23 May 2022 09:29:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232903AbiEWJ3O (ORCPT ); Mon, 23 May 2022 05:29:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33464 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232889AbiEWJ3M (ORCPT ); Mon, 23 May 2022 05:29:12 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8E5414927C; Mon, 23 May 2022 02:29:11 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 48DE121A57; Mon, 23 May 2022 09:29:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1653298150; 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=yKSiy0ipOYVbqRPh0+sMS6w58vGVnmR5krmIKhBhvCo=; b=rhER0KTpLC+kN7FEVjQD6D5ygjKKlG/FidSbAufFle/t6d05K+2srPjx2V5Ec/NWBqGhss lklFclXZMR8sHsK0D1N7g1+tqpbbb3NC9Wuf6obFB/NFdR26vGPNTLq1U2UcvMQ1iRLBrK JiOeSW48sRlLrIuWLgCeycrkMzd8J/g= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1653298150; 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=yKSiy0ipOYVbqRPh0+sMS6w58vGVnmR5krmIKhBhvCo=; b=00foDO6puATmPZsCtmjAr17KPhXXoPethprIX1ioU1ZZc6K2o0pA+ZbMOs5OQmWH7FPwwt fFvBdQO7vYv8jvDA== 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 DF7B12C141; Mon, 23 May 2022 09:29:09 +0000 (UTC) Received: by quack3.suse.cz (Postfix, from userid 1000) id 671CEA0632; Mon, 23 May 2022 11:29:08 +0200 (CEST) Date: Mon, 23 May 2022 11:29:08 +0200 From: Jan Kara To: Baokun Li Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, ritesh.list@gmail.com, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yebin10@huawei.com, yukuai3@huawei.com, Hulk Robot Subject: Re: [PATCH 1/2] ext4: fix bug_on ext4_mb_use_inode_pa Message-ID: <20220523092908.2ghn2fvps5dfhyz3@quack3.lan> References: <20220521134217.312071-1-libaokun1@huawei.com> <20220521134217.312071-2-libaokun1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220521134217.312071-2-libaokun1@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Sat 21-05-22 21:42:16, Baokun Li wrote: > Hulk Robot reported a BUG_ON: > ================================================================== > kernel BUG at fs/ext4/mballoc.c:3211! > [...] > RIP: 0010:ext4_mb_mark_diskspace_used.cold+0x85/0x136f > [...] > Call Trace: > ext4_mb_new_blocks+0x9df/0x5d30 > ext4_ext_map_blocks+0x1803/0x4d80 > ext4_map_blocks+0x3a4/0x1a10 > ext4_writepages+0x126d/0x2c30 > do_writepages+0x7f/0x1b0 > __filemap_fdatawrite_range+0x285/0x3b0 > file_write_and_wait_range+0xb1/0x140 > ext4_sync_file+0x1aa/0xca0 > vfs_fsync_range+0xfb/0x260 > do_fsync+0x48/0xa0 > [...] > ================================================================== > > Above issue may happen as follows: > ------------------------------------- > do_fsync > vfs_fsync_range > ext4_sync_file > file_write_and_wait_range > __filemap_fdatawrite_range > do_writepages > ext4_writepages > mpage_map_and_submit_extent > mpage_map_one_extent > ext4_map_blocks > ext4_mb_new_blocks > ext4_mb_normalize_request > >>> start + size <= ac->ac_o_ex.fe_logical > ext4_mb_regular_allocator > ext4_mb_simple_scan_group > ext4_mb_use_best_found > ext4_mb_new_preallocation > ext4_mb_new_inode_pa > ext4_mb_use_inode_pa > >>> set ac->ac_b_ex.fe_len <= 0 > ext4_mb_mark_diskspace_used > >>> BUG_ON(ac->ac_b_ex.fe_len <= 0); > > we can easily reproduce this problem with the following commands: > `fallocate -l100M disk` > `mkfs.ext4 -b 1024 -g 256 disk` > `mount disk /mnt` > `fsstress -d /mnt -l 0 -n 1000 -p 1` > > The size must be smaller than or equal to EXT4_BLOCKS_PER_GROUP. > Therefore, "start + size <= ac->ac_o_ex.fe_logical" may occur > when the size is truncated. So start should be the start position of > the group where ac_o_ex.fe_logical is located after alignment. > In addition, when the value of fe_logical or EXT4_BLOCKS_PER_GROUP > is very large, the value calculated by start_off is more accurate. > > Fixes: cd648b8a8fd5 ("ext4: trim allocation requests to group size") > Reported-by: Hulk Robot > Signed-off-by: Baokun Li Looks good. I'd just phrase the comment below a bit differently: > + /* > + * Because size must be less than or equal to > + * EXT4_BLOCKS_PER_GROUP, start should be the start position of > + * the group where ac_o_ex.fe_logical is located after alignment. > + * In addition, when the value of fe_logical or > + * EXT4_BLOCKS_PER_GROUP is very large, the value calculated > + * by start_off is more accurate. > + */ > + start = max(start, round_down(ac->ac_o_ex.fe_logical, > + EXT4_BLOCKS_PER_GROUP(ac->ac_sb))); > + Can we make the comment like: /* * For tiny groups (smaller than 8MB) the chosen allocation * alignment may be larger than group size. Make sure the alignment * does not move allocation to a different group which makes mballoc * fail assertions later. */ With that feel free to add: Reviewed-by: Jan Kara Honza -- Jan Kara SUSE Labs, CR