If a fuse_loop instance dies suddenly (e.g. SIGKILL), the FUSE mount and
loop device assignment are left behind. We can determine this scenario
on specific unmap, when the PID file is either missing or contains a PID
of a non-running process, but the backing file and potentially loop
device are still there.
If that's the case, do an "emergency cleanup", by unassigning the
loopdev, calling 'fusermount -u' and then cleaning any leftover files
manually.
With this in place, pretty much any situation is now recoverable via
only the 'proxmox-backup-client' binary, by either calling 'unmap' with
or without parameters.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
On unmap, only report success if the instance we are killing actually
terminates. This is especially important so that cleanup routines can be
assured that /run files are actually cleaned up after calling
cleanup_unused_run_files.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
A 'map' call will only clean up what it needs, that is only leftover
files or dangling instances of it's own name.
For a full cleanup the user can call 'unmap' without any arguments.
The 'cleanup on error' behaviour of map_loop is removed. It is no longer
needed (since the next call will clean up anyway), and in fact fixes a
bug where trying to map an image twice would result in an error, but
also cleanup the .pid file of the running instance, causing 'unmap' to
fail afterwards.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
So user doesn't need to remember which loop devices he has mapped to
what.
systemd unit encoding is used to transform a unique identifier for the
mapped image into a suitable name. The files created in /run/pbs-loopdev
will be named accordingly.
The encoding all happens outside fuse_loop.rs, so the fuse_loop module
does not need to care about encodings - it can always assume a name is a
valid filename.
'unmap' without parameter displays all current mappings. It's
autocompletion handler will list the names of all currently mapped
images for easy selection. Unmap by /dev/loopX or loopdev number is
maintained, as those can be distinguished from mapping names.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
Allows mapping fixed-index .img files (usually from VM backups) to be
mapped to a local loopback device.
The architecture uses a FUSE-backed temp file mapped to a loopdev:
/dev/loopX -> FUSE /run/pbs-loopdev/xxx -> backup client -> PBS
Since unmapping requires some cleanup (unmap the loopdev, stop FUSE,
remove the temp files) a special 'unmap' command is added, which uses a
PID file to send SIGINT to the backup-client instance started with
'map', which will handle the cleanup itself.
The polling with select! in mount.rs needs to be split in two, since we
have a chicken and egg problem between running FUSE and setting up the
loop device - so we need to do them concurrently, until the loopdev is
assigned, at which point we can report success and daemonize, and then
continue polling the FUSE loop future.
A loopdev module is added to tools containing all required functions for
mapping a loop device to the FUSE file, with the ioctls moved into an
inline module to avoid exposing them directly.
The client code is placed in the 'mount' module, which, while
admittedly a loose fit, allows reuse of the daemonizing code.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
Wolfgang Bumiller
Stefan Reiter