The mknod() method currently allows passing no dir_fd, in which case an
internal one is opened. This FD is then never closed, though.
Fix this by simply making the dir_fd mandatory. All callers pass it
(there is actually only a single caller), so no need for the fallback.
Don't wait until python's garbage collector closes the file descriptors
to loop devices. Close them when the `LoopServer` context manager exits,
after an assembler has finished running.
Support the LOOP_SET_DIRECT_IO ioctl, which alows us to control
whether or not a loopback device should perform its own buffering
or rely on the one done by the underlying backing file.
Enabling this should improve both throughput and memory consumption,
it is not currently hooked up as more testing would be required.
loop.py is a simple wrapper around the kernel loop API. remoteloop.py
uses this to create a server/clinet pair that communicates over an
AF_UNIX/SOCK_DGRAM socket to allow the server to create loop devices
for the client.
The client passes a fd that should be bound to the resulting loop
device, and a dir-fd where the loop device node should be created.
The server returns the name of the device node to the client.
The idea is that the client is run from whithin a container without
access to devtmpfs (and hence /dev/loop-control), and the server
runs on the host. The client would typically pass its (fake) /dev
as the output directory.
For the client this will be similar to `losetup -f foo.img --show`.
[@larskarlitski: pylint: ignore the new LoopInfo class, because it
only has dynamic attributes. Also disable attribute-defined-outside-init,
which (among other problems) is not ignored for that class.]
Signed-off-by: Tom Gundersen <teg@jklm.no>
