Btrfs: do not mark the chunk as readonly if in degraded mode

Btrfs: do not mark the chunk as readonly if in degraded mode

commit f48b90756bd834dda852ff514f2690d3175b1f44 upstream.

If a RAID setup has chunks that span multiple disks, and one of those
disks has failed, btrfs_chunk_readonly will return 1 since one of the
disks in that chunk's stripes is dead and therefore not writeable.  So
instead if we are in degraded mode, return 0 so we can go ahead and
allocate stuff.  Without this patch all of the block groups in a RAID1
setup will end up read-only, which will mean we can't add new disks to
the array since we won't be able to make allocations.

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Acked-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>