From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1050.oracle.com ([141.146.126.70]:34396 "EHLO aserp1050.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752964AbcLOG5h (ORCPT ); Thu, 15 Dec 2016 01:57:37 -0500 Received: from aserp1040.oracle.com (aserp1040.oracle.com [141.146.126.69]) by aserp1050.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id uBF6vTPq028702 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Thu, 15 Dec 2016 06:57:29 GMT From: Liu Bo To: linux-btrfs@vger.kernel.org Cc: David Sterba Subject: [PATCH] Btrfs: fix another race between truncate and lockless dio write Date: Wed, 14 Dec 2016 23:04:05 -0800 Message-Id: <1481785445-13329-1-git-send-email-bo.li.liu@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Dio writes can update i_size in btrfs_get_blocks_direct when it writes to offset beyond EOF so that endio can update disk_i_size correctly (because we don't udpate disk_i_size beyond i_size). However, when truncating down a file, we firstly update i_size and then wait for in-flight lockless dio reads/writes, according to the above, i_size may have been changed in dio writes, and file extents don't get truncated. For lockless dio writes are always overwrites, i_size is not supposed to be changed, so this adds a check to filter out this case. The race could be reproduced by fstests/generic/299 with patch "Btrfs: fix btrfs_ordered_update_i_size to update disk_i_size properly" applied. Signed-off-by: Liu Bo --- fs/btrfs/inode.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index c9973e5..171d8e8 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -72,6 +72,7 @@ struct btrfs_dio_data { u64 reserve; u64 unsubmitted_oe_range_start; u64 unsubmitted_oe_range_end; + int overwrite; }; static const struct inode_operations btrfs_dir_inode_operations; @@ -7833,7 +7834,7 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, * Need to update the i_size under the extent lock so buffered * readers will get the updated i_size when we unlock. */ - if (start + len > i_size_read(inode)) + if (!dio_data->overwrite && start + len > i_size_read(inode)) i_size_write(inode, start + len); adjust_dio_outstanding_extents(inode, dio_data, len); @@ -8715,6 +8716,7 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) * not unlock the i_mutex at this case. */ if (offset + count <= inode->i_size) { + dio_data.overwrite = 1; inode_unlock(inode); relock = true; } -- 2.5.5