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 26042C433F5 for ; Mon, 23 May 2022 09:58:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233615AbiEWJ6Z (ORCPT ); Mon, 23 May 2022 05:58:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233645AbiEWJ6O (ORCPT ); Mon, 23 May 2022 05:58:14 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C743F403EB for ; Mon, 23 May 2022 02:58:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1653299892; 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=OVQygW/WRePQfq33h+NUTgse8308ziOIB4rNgjq1sRo=; b=M8fYOO69kVfuWkSYu0KbSbwFj75bdjpwffPHBXHrs5jwDFsj8mCNP2kxGGHcGKY1hAOT6t QiAWyZKwVc2Bm9uPBSrftfjR1X2UZbQPCtbu49H5BxtnnnAyV8733sSpyYqGbJGXyr8ofU Cf/3WPzedoBDQXpiludgqlKoL0VGInA= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-645-8WMgEsrrPLykg32nwdRpSQ-1; Mon, 23 May 2022 05:58:08 -0400 X-MC-Unique: 8WMgEsrrPLykg32nwdRpSQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1A021833961; Mon, 23 May 2022 09:58:08 +0000 (UTC) Received: from fedora (unknown [10.40.194.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2D2D61121314; Mon, 23 May 2022 09:58:05 +0000 (UTC) Date: Mon, 23 May 2022 11:58:03 +0200 From: Lukas Czerner 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: <20220523095803.gomx2q62ymocrkrz@fedora> 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> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 21, 2022 at 09:42:16PM +0800, 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 > --- > fs/ext4/mballoc.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c > index ea653d19f9ec..32410b79b664 100644 > --- a/fs/ext4/mballoc.c > +++ b/fs/ext4/mballoc.c > @@ -4107,6 +4107,17 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac, > size = size >> bsbits; > start = start_off >> bsbits; > > + /* > + * 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))); This does not look right. The second argument in round_down() must be a power of two, but there is no such restriction on blocks per group. Also I am not quite sure why do we adjust the start in this way at all? If we found what seems to be a preallocated extent which we can use and we're actually going to use 0 lenght extent it seems like the problem is somewhere else? Can you desribe the problem a bit more in detail? Maybe I need to look at the ext4_mb_normalize_request() some more. -Lukas > + > /* don't cover already allocated blocks in selected range */ > if (ar->pleft && start <= ar->lleft) { > size -= ar->lleft + 1 - start; > -- > 2.31.1 >