Due to either bugs in send (kernel) that generate a command against
a wrong path for example, or transient errors on the receiving side,
we stopped processing the send stream immediately and exited with
an error.
It's often desirable to continue processing the send stream even if an
error happens while processing a single command from the send stream.
This change just adds a --max-errors <N> parameter, whose default value
is 1 (preserving current behaviour), that allows to tolerate N errors
before stopping. A value of 0 means to never stop no matter how many
errors we get into while processing the send stream. Regardless of its
value, errors are always printed to stderr when they happen, just like
before this change.
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
A new option is added to btrfs-receive to change the behavior when
an <end cmd> 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
<end cmd> is received, afterwards either an EOF or a new
<stream header> is expected.
The new behavior (if the -e option is set on the command line) is
to terminate after an <end cmd> 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):
<stream header> + <sequence of commands> + <end cmd> +
<stream header> + <sequence of commands> + <end cmd> + EOF
If the new -e option is set, the expected format is like this:
<stream header> + <sequence of commands> +
<sequence of commands> + <end cmd>
The btrfs-send tool is changed in a seperate commit to always use
the new format, i.e. to send an <end cmd> only at the end.
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.
The goal of changing the semantic of <end cmd> 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.
Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
The flag and command are synced from kernel to user. Also, this patch adds a
callback for the BTRFS_SEND_C_UPDATE_EXTENT in struct btrfs_send_ops.
read_and_process_cmd() is updated to decode BTRFS_SEND_C_UPDATE_EXTENT and
send the values through the right callback. I did not add a callback
definition to cmds-receive.c as that code never uses
BTRFS_SEND_FLAG_NO_FILE_DATA.
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Add user space commands for btrfs send/receive.
Signed-off-by: Alexander Block <ablock84@googlemail.com>
Reviewed-by: David Sterba <dave@jikos.cz>
Reviewed-by: Arne Jansen <sensille@gmx.net>
Reviewed-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Reviewed-by: Alex Lyakas <alex.bolshoy.btrfs@gmail.com>
Filipe David Borba Manana
Stefan Behrens
Mark Fasheh
Alexander Block