Fill missing devices so degraded filesystems can be read

When a device is missing, the btrfs tools need to be able to read alternate
copies from the remaining devices.  This creates placeholder devices
that always return -EIO so the tools can limp along.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/disk-io.c b/disk-io.c
index a6e1000d..fef3edab 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -204,6 +204,7 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 		eb->dev_bytenr = multi->stripes[0].physical;
 		kfree(multi);
 		ret = read_extent_from_disk(eb);
+
 		if (ret == 0 && check_tree_block(root, eb) == 0 &&
 		    csum_tree_block(root, eb, 1) == 0 &&
 		    verify_parent_transid(eb->tree, eb, parent_transid) == 0) {