path: root/include/uapi
diff options
authorStefan Behrens <sbehrens@giantdisaster.de>2013-04-10 17:10:52 +0000
committerJosef Bacik <jbacik@fusionio.com>2013-05-06 15:54:44 -0400
commitc2c71324ecb471c932bc1ff59e46ffcf82f274fc (patch)
tree8de6bb57594560bf381e4e5cc9bfaccc8e3caf60 /include/uapi
parent692206b153ea0d08d6015521ed27a6739cbf6f9f (diff)
Btrfs: allow omitting stream header and end-cmd for btrfs send
Two new flags are added to allow omitting the stream header and the end command for btrfs send streams. This is used in cases where you send multiple snapshots back-to-back in one stream. This used to be encoded like this (with 2 snapshots in this example): <stream header> + <sequence of commands> + <end cmd> + <stream header> + <sequence of commands> + <end cmd> + EOF The new format (if the two new flags are used) is this one: <stream header> + <sequence of commands> + <sequence of commands> + <end cmd> Note that the currently existing receivers treat <end cmd> only as an indication that a new <stream header> is following. This means, you can just skip the sequence <end cmd> <stream header> without loosing compatibility. As long as an EOF is following, the currently existing receivers handle the new format (if the two new flags are used) exactly as the old one. So what is the benefit of this change? The goal is to be able to use a single stream (one TCP connection) to multiplex a request/response handshake plus Btrfs send streams, all in the same stream. In this case you cannot evaluate an EOF condition as an end of the Btrfs send stream. You need something else, and the <end cmd> is just perfect for this purpose. The summary is: The format change is driven by the need to send several Btrfs send streams over a single TCP connections, with the ability for a repeated request/response handshake in the middle. And this format change does not break any existing tool, it is completely compatible. You could compare the old behaviour of the Btrfs send stream to the one of ftp where you need a seperate request/response channel and newly opened data transfer channels for each file, while the new behaviour is more like http using a single stream for everything. Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de> Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Diffstat (limited to 'include/uapi')
1 files changed, 19 insertions, 1 deletions
diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index fa3a5f9338f..5e39e859a84 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -412,7 +412,25 @@ struct btrfs_ioctl_received_subvol_args {
* search of clone sources doesn't find an extent. UPDATE_EXTENT
* commands will be sent instead of WRITE commands.
+ * Do not add the leading stream header. Used when multiple snapshots
+ * are sent back to back.
+ */
+ * Omit the command at the end of the stream that indicated the end
+ * of the stream. This option is used when multiple snapshots are
+ * sent back to back.
+ */
struct btrfs_ioctl_send_args {
__s64 send_fd; /* in */