[PATCH 3.16 056/366] Btrfs: fix unexpected cow in run_delalloc_nocow

Ben Hutchings
2018-10-14T23:24:42Z

From: Liu Bo <bo.li.liu@oracle.com>

commit 5811375325420052fcadd944792a416a43072b7f upstream.

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.

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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1145,6 +1145,8 @@ static noinline int csum_exist_in_range(
list_del(&sums->list);
kfree(sums);
}
+ if (ret < 0)
+ return ret;
return 1;
}

@@ -1294,10 +1296,23 @@ next_slot:
goto out_check;
if (btrfs_extent_readonly(root, disk_bytenr))
goto out_check;
- if (btrfs_cross_ref_exist(trans, root, ino,
- found_key.offset -
- extent_offset, disk_bytenr))
+ ret = btrfs_cross_ref_exist(trans, 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;
@@ -1315,8 +1330,22 @@ next_slot:
* this ensure that csum for a given extent are
* either valid or do not exist.
*/
- if (csum_exist_in_range(root, disk_bytenr, num_bytes))
+ ret = csum_exist_in_range(root, disk_bytenr,
+ num_bytes);
+ 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;
+ }
nocow = 1;
} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
extent_end = found_key.offset +