Add a notification mechanism for signaling when the mountpoint is ready

[ariel-miculas]

Add the notify_pipe option which allows the user to specify the path to a named pipe. When the mountpoint is ready, a message will be written to this pipe: 's' for success and 'f' for failure. To avoid blocking the fuse process until the pipe is read, a new process is spawned which performs a blocking operation on the pipe. In case of mount failure, no additional process is created and the main process blocks until the pipe is read.

An example of operation is provided below:

set -x
FIFO=$(mktemp -u)
mkfifo "$FIFO"
./squashfuse_ll -o notify_pipe="$FIFO" -f /path/to/squashfs/archive /tmp/squash&
STATUS=$(head -c1 "$FIFO")
if [ "$STATUS" = "s" ]; then
    echo "Mountpoint contains:"
    ls /tmp/squash
else
    echo "Mounting squashfuse on /tmp/squash failed"
fi

Fixes #49

[DrDaveD]

Is there any reason why this can't be done with squashfuse as well as squashfuse_ll?

[ariel-miculas]

No, I'll add this to squashfuse also.

[DrDaveD]

The code looks pretty good to me now (although the CI checks are running at the moment). Please also add the new option to the squashfuse.1 man page and add an automated test or tests.

[vasi]

Added some comments, but overall looks great!

[ariel-miculas]

Thanks, @vasi. I've addressed your comments, updated the squashfuse.1 manpage and modified some tests in ll-smoke.sh.in to use this new notification mechanism.

[DrDaveD]

The new new smoke test unfortunately failed on the freebsd check. Look for FAIL:. It says

Image mounted successfully when it should have failed

[ariel-miculas]

Thanks, I was looking for this log but couldn't find it. So it's probably fine to overmount squashfuse on top of an existing squashfuse mountpoint on freebsd, I need to change the test to make it fail the mount in other ways.

[ariel-miculas]

I'm still awaiting approval for one workflow.

[DrDaveD]

Thanks for the reminder, I'm sorry I didn't notice the push. The good news was that freebsd passed. I now approved the workflow.

[DrDaveD]

This isn't fully working, see #112