From 4aaedfb0b68ca83471c5f10f1da7f0f4714080a1 Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Wed, 14 Dec 2016 22:36:05 -0800 Subject: [PATCH] Btrfs: fix another race between truncate and lockless dio write 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 Signed-off-by: David Sterba --- 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 29ad99a2e287..70f932d4b69d 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -71,6 +71,7 @@ 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; @@ -7809,7 +7810,7 @@ unlock: * 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); @@ -8685,6 +8686,7 @@ 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; } -- 2.30.2