From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([59.151.112.132]:10220 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1755946AbdELDa5 (ORCPT ); Thu, 11 May 2017 23:30:57 -0400 From: Qu Wenruo To: , CC: Subject: [RFC PATCH v3.1 4/6] btrfs: qgroup: Fix qgroup reserved space underflow caused by buffered write and quota enable Date: Fri, 12 May 2017 11:30:44 +0800 Message-ID: <20170512033046.31981-5-quwenruo@cn.fujitsu.com> In-Reply-To: <20170512033046.31981-1-quwenruo@cn.fujitsu.com> References: <20170512033046.31981-1-quwenruo@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-btrfs-owner@vger.kernel.org List-ID: [BUG] Under the following case, we can underflow qgroup reserved space. Task A | Task B --------------------------------------------------------------- Quota disabled | Buffered write | |- btrfs_check_data_free_space() | | *NO* qgroup space is reserved | | since quota is *DISABLED* | |- All pages are copied to page | cache | | Enable quota | Quota scan finished | | Sync_fs | |- run_delalloc_range | |- Write pages | |- btrfs_finish_ordered_io | |- insert_reserved_file_extent | |- btrfs_qgroup_release_data() | Since no qgroup space is reserved in Task A, we underflow qgroup reserved space This can be detected by fstest btrfs/104. [CAUSE] In insert_reserved_file_extent() we info qgroup to release the @ram_bytes size of qgroup reserved_space under all case. And btrfs_qgroup_release_data() will check if qgroup is enabled. However in above case, the buffered write happens before quota is enabled, so we don't havee reserved space for that range. [FIX] In insert_reserved_file_extent(), we info qgroup to release the acctual byte number it released. In above case, since we don't have reserved space, we info qgroup to release 0 byte, so the problem can be fixed. And thanks to the @reserved parameter introduced by qgroup rework, and previous patch to return release bytes, the fix can be as small as less than 10 lines. Signed-off-by: Qu Wenruo --- fs/btrfs/inode.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 17cbe9306faf..a1294d5baef5 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -2143,6 +2143,7 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans, struct btrfs_path *path; struct extent_buffer *leaf; struct btrfs_key ins; + u64 qg_released; int extent_inserted = 0; int ret; @@ -2198,13 +2199,17 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans, ins.objectid = disk_bytenr; ins.offset = disk_num_bytes; ins.type = BTRFS_EXTENT_ITEM_KEY; - ret = btrfs_alloc_reserved_file_extent(trans, root->root_key.objectid, - btrfs_ino(BTRFS_I(inode)), file_pos, ram_bytes, &ins); + /* * Release the reserved range from inode dirty range map, as it is * already moved into delayed_ref_head */ - btrfs_qgroup_release_data(inode, file_pos, ram_bytes); + ret = btrfs_qgroup_release_data(inode, file_pos, ram_bytes); + if (ret < 0) + goto out; + qg_released = ret; + ret = btrfs_alloc_reserved_file_extent(trans, root->root_key.objectid, + btrfs_ino(BTRFS_I(inode)), file_pos, qg_released, &ins); out: btrfs_free_path(path); -- 2.12.2