Add a simple check that data written through the loop device is
actually ending up in the file. NB: this this will _fail_ if the
fd is cleared via `clear_fd` without the use of `flush_buf`. It
seems that the kernel (as of 5.13.8) will indeed not clear the
buffer cache of the loop device if the backing file is detached
via `LOOP_CLR_FD`. On the other hand, if the autoclear flag is,
i.e. the backing file cleared when the last file descriptor of
the loop device is closed, the buffer cached will be cleared as
part of the `release` operation of the block device.
Add support for locking the loopback block device via `flock(2)`.
The main use case for this is to prevent systemd-udevd from
proben the device while any modification is done to it. See the
systemd page, https://www.freedesktop.org/software/systemd, for
more details.
Add the corresponding tests to it.
Add a helper method that clears the fd for a given loop device but
also ensures that the loop device is not bound to the supplied fd
anymore. Check the function documentation for more information.
Add a corresponding test.
Add a `Loop.is_bound_to` helper that checks if the looback device is
bound if is so if the backing file refers to the same file as `fd`.
The latter is done by comparing the device and inode information.
Add a helper that will check if the loop devices is backed by
the file identified via the stat(2) result, i.e. the inode on
the correspoding device.
Add a correspoding test for the new helper.
Implement a `Loop.get_status` method, to get the properties of the
loop device, corresponding to LOOP_GET_STATUS64, and counterpart
to the existing `Loop.set_status` method. Use the new `get_status`
call in the `set_status` call, replacing the existing code that
does the same thing.
Add a basic test for the `get_status` method. Also fix an actual
leak, where the loop device was closed but the fd was not cleared
inside the test.
