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Subject[PATCH 4.9 054/101] Btrfs: fix unexpected cow in run_delalloc_nocow
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

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.

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>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
fs/btrfs/inode.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)

--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1230,6 +1230,8 @@ static noinline int csum_exist_in_range(
list_del(&sums->list);
kfree(sums);
}
+ if (ret < 0)
+ return ret;
return 1;
}

@@ -1381,10 +1383,23 @@ next_slot:
goto out_check;
if (btrfs_extent_readonly(root, disk_bytenr))
goto out_check;
- if (btrfs_cross_ref_exist(trans, root, ino,
+ ret = btrfs_cross_ref_exist(trans, root, ino,
found_key.offset -
- extent_offset, disk_bytenr))
+ 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;
@@ -1402,8 +1417,20 @@ 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;
+ }
if (!btrfs_inc_nocow_writers(root->fs_info,
disk_bytenr))
goto out_check;

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