From 46de1a6ec3dbb0db203baa6c46cb64ba9b000ea2 Mon Sep 17 00:00:00 2001 From: Stefan Behrens Date: Tue, 9 Apr 2013 19:08:40 +0200 Subject: Btrfs-progs: btrfs-receive optionally honors the end-cmd A new option is added to btrfs-receive to change the behavior when an is received in the Btrfs send stream. The traditional behavior (which still is the default) is to continue to read the stream until an EOF condition is encountered. If an is received, afterwards either an EOF or a new is expected. The new behavior (if the -e option is set on the command line) is to terminate after an is read without the need for an EOF. This allows the stream (e.g. a single TCP stream) to carry additional data or even multiple Btrfs send streams. Old btrfs-send tools used to encode multiple snapshots like this (with 2 snapshots in this example): + + + + + + EOF If the new -e option is set, the expected format is like this: + + + The btrfs-send tool is changed in a seperate commit to always use the new format, i.e. to send an only at the end. Note that the currently existing receivers treat only as an indication that a new is following. This means, you can just skip the sequence 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. The goal of changing the semantic of 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 is just perfect for this purpose. Signed-off-by: Stefan Behrens --- cmds-receive.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) (limited to 'cmds-receive.c') diff --git a/cmds-receive.c b/cmds-receive.c index 97952763..90e26d25 100644 --- a/cmds-receive.c +++ b/cmds-receive.c @@ -66,6 +66,8 @@ struct btrfs_receive struct subvol_info *cur_subvol; struct subvol_uuid_search sus; + + int honor_end_cmd; }; static int finish_subvol(struct btrfs_receive *r) @@ -810,7 +812,8 @@ int do_receive(struct btrfs_receive *r, const char *tomnt, int r_fd) goto out; while (!end) { - ret = btrfs_read_and_process_send_stream(r_fd, &send_ops, r); + ret = btrfs_read_and_process_send_stream(r_fd, &send_ops, r, + r->honor_end_cmd); if (ret < 0) goto out; if (ret) @@ -863,7 +866,7 @@ static int do_cmd_receive(int argc, char **argv) r.mnt_fd = -1; r.write_fd = -1; - while ((c = getopt(argc, argv, "vf:")) != -1) { + while ((c = getopt(argc, argv, "evf:")) != -1) { switch (c) { case 'v': g_verbose++; @@ -871,6 +874,9 @@ static int do_cmd_receive(int argc, char **argv) case 'f': fromfile = optarg; break; + case 'e': + r.honor_end_cmd = 1; + break; case '?': default: fprintf(stderr, "ERROR: receive args invalid.\n"); @@ -904,7 +910,7 @@ static const char * const receive_cmd_group_usage[] = { }; const char * const cmd_receive_usage[] = { - "btrfs receive [-v] [-f ] ", + "btrfs receive [-ve] [-f ] ", "Receive subvolumes from stdin.", "Receives one or more subvolumes that were previously ", "sent with btrfs send. The received subvolumes are stored", @@ -920,6 +926,10 @@ const char * const cmd_receive_usage[] = { "-f By default, btrfs receive uses stdin", " to receive the subvolumes. Use this", " option to specify a file to use instead.", + "-e Terminate after receiving an ", + " in the data stream. Without this option,", + " the receiver terminates only if an error", + " is recognized or on EOF.", NULL }; -- cgit v1.2.3