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 9076CC77B6F for ; Tue, 11 Apr 2023 14:11:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229848AbjDKOLO (ORCPT ); Tue, 11 Apr 2023 10:11:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41894 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230274AbjDKOLF (ORCPT ); Tue, 11 Apr 2023 10:11:05 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B39094C1C; Tue, 11 Apr 2023 07:10:52 -0700 (PDT) Received: from dggpeml500021.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4PwnlX3wbZzrZn5; Tue, 11 Apr 2023 22:09:28 +0800 (CST) Received: from [10.174.177.174] (10.174.177.174) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Tue, 11 Apr 2023 22:10:50 +0800 Message-ID: Date: Tue, 11 Apr 2023 22:10:50 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [PATCH v2 1/2] ext4: only update i_reserved_data_blocks on successful block allocation Content-Language: en-US To: Jan Kara CC: , , , , , , , , Baokun Li References: <20230406132834.1669710-1-libaokun1@huawei.com> <20230406132834.1669710-2-libaokun1@huawei.com> <20230411090800.rrsvbab3tio7rs2m@quack3> From: Baokun Li In-Reply-To: <20230411090800.rrsvbab3tio7rs2m@quack3> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.174] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500021.china.huawei.com (7.185.36.21) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/4/11 17:08, Jan Kara wrote: > On Thu 06-04-23 21:28:33, Baokun Li wrote: >> In our fault injection test, we create an ext4 file, migrate it to >> non-extent based file, then punch a hole and finally trigger a WARN_ON >> in the ext4_da_update_reserve_space(): >> >> EXT4-fs warning (device sda): ext4_da_update_reserve_space:369: >> ino 14, used 11 with only 10 reserved data blocks >> >> When writing back a non-extent based file, if we enable delalloc, the >> number of reserved blocks will be subtracted from the number of blocks >> mapped by ext4_ind_map_blocks(), and the extent status tree will be >> updated. We update the extent status tree by first removing the old >> extent_status and then inserting the new extent_status. If the block range >> we remove happens to be in an extent, then we need to allocate another >> extent_status with ext4_es_alloc_extent(). >> >> use old to remove to add new >> |----------|------------|------------| >> old extent_status >> >> The problem is that the allocation of a new extent_status failed due to a >> fault injection, and __es_shrink() did not get free memory, resulting in >> a return of -ENOMEM. Then do_writepages() retries after receiving -ENOMEM, >> we map to the same extent again, and the number of reserved blocks is again >> subtracted from the number of blocks in that extent. Since the blocks in >> the same extent are subtracted twice, we end up triggering WARN_ON at >> ext4_da_update_reserve_space() because used > ei->i_reserved_data_blocks. >> >> For non-extent based file, we update the number of reserved blocks after >> ext4_ind_map_blocks() is executed, which causes a problem that when we call >> ext4_ind_map_blocks() to create a block, it doesn't always create a block, >> but we always reduce the number of reserved blocks. So we move the logic >> for updating reserved blocks to ext4_ind_map_blocks() to ensure that the >> number of reserved blocks is updated only after we do succeed in allocating >> some new blocks. >> >> Fixes: 5f634d064c70 ("ext4: Fix quota accounting error with fallocate") >> Signed-off-by: Baokun Li > Looks good, just one nit below. > >> diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c >> index c68bebe7ff4b..9acab70ddf5e 100644 >> --- a/fs/ext4/indirect.c >> +++ b/fs/ext4/indirect.c >> @@ -651,6 +651,14 @@ int ext4_ind_map_blocks(handle_t *handle, struct inode *inode, >> >> ext4_update_inode_fsync_trans(handle, inode, 1); >> count = ar.len; >> + >> + /* >> + * Update reserved blocks/metadata blocks after successful block >> + * allocation which had been deferred till now. >> + */ >> + if ((count > 0) && (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)) > You don't need the count > 0 condition here. It should be always true. > > Honza > Indeed! Thanks a million! I will remove this condition in patch v3. -- With Best Regards, Baokun Li .