Permit writing to directory only when SAN is mounted

Question

The problem statement is this: I have a directory which is configured as a mountpoint for a SAN partition. Now this SAN partition gets mounted several minutes after boot due to some reasons which I cannot avoid. In the meantime, some processes start writing to the directory (which is still not on SAN and just a local directory), thereby causing trouble.

My goal is to ensure that I do not allow any process to write in the directory while it is local. As soon as SAN gets mounted on it, the processes are free to write.

Answer 1

Make the mount point immutable:

# chattr +i /mnt/foo

Verify that you cannot write there:

# touch /mnt/foo/hello
touch: cannot touch ‘/srv/test/foo’: Permission denied

And now perform the mount:

# mount /dev/foo /mnt/foo