The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5811375325420052fcadd944792a416a43072b7f Mon Sep 17 00:00:00 2001

From: Liu Bo bo.li.liu@oracle.com Date: Wed, 31 Jan 2018 17:09:13 -0700 Subject: [PATCH] Btrfs: fix unexpected cow in run_delalloc_nocow

Fstests generic/475 provides a way to fail metadata reads while checking if checksum exists for the inode inside run_delalloc_nocow(), and csum_exist_in_range() interprets error (-EIO) as inode having checksum and makes its caller enter the cow path.

In case of free space inode, this ends up with a warning in cow_file_range().

The same problem applies to btrfs_cross_ref_exist() since it may also read metadata in between.

With this, run_delalloc_nocow() bails out when errors occur at the two places.

cc: stable@vger.kernel.org v2.6.28+ Fixes: 17d217fe970d ("Btrfs: fix nodatasum handling in balancing code") Signed-off-by: Liu Bo bo.li.liu@oracle.com Signed-off-by: David Sterba dsterba@suse.com

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 6504e63b2317..491a7397f6fa 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1256,6 +1256,8 @@ static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info, list_del(&sums->list); kfree(sums); } + if (ret < 0) + return ret; return 1; }

@@ -1388,10 +1390,23 @@ static noinline int run_delalloc_nocow(struct inode *inode, goto out_check; if (btrfs_extent_readonly(fs_info, disk_bytenr)) goto out_check; - if (btrfs_cross_ref_exist(root, ino, - found_key.offset - - extent_offset, disk_bytenr)) + ret = btrfs_cross_ref_exist(root, ino, + found_key.offset - + extent_offset, disk_bytenr); + if (ret) { + /* + * ret could be -EIO if the above fails to read + * metadata. + */ + if (ret < 0) { + if (cow_start != (u64)-1) + cur_offset = cow_start; + goto error; + } + + WARN_ON_ONCE(nolock); goto out_check; + } disk_bytenr += extent_offset; disk_bytenr += cur_offset - found_key.offset; num_bytes = min(end + 1, extent_end) - cur_offset; @@ -1409,10 +1424,22 @@ static noinline int run_delalloc_nocow(struct inode *inode, * this ensure that csum for a given extent are * either valid or do not exist. */ - if (csum_exist_in_range(fs_info, disk_bytenr, - num_bytes)) { + ret = csum_exist_in_range(fs_info, disk_bytenr, + num_bytes); + if (ret) { if (!nolock) btrfs_end_write_no_snapshotting(root); + + /* + * ret could be -EIO if the above fails to read + * metadata. + */ + if (ret < 0) { + if (cow_start != (u64)-1) + cur_offset = cow_start; + goto error; + } + WARN_ON_ONCE(nolock); goto out_check; } if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr)) {