[PATCH 0/4 v3][focal:linux-azure] cifs: On cifs_reconnect, resolve the hostname again

[Tim Gardner]

v2 - Added an LP BugLink.
v3 - Added 0bf1bafb17df03fbd0e8b9a086c39e6f24af7193 ("cifs: Avoid error pointer dereference")
     to correctly return from an error case.

BugLink: https://bugs.launchpad.net/bugs/1929831

Microsoft has asked to have commit commit 4e456b30f78c429b183db420e23b26cde7e03a78 applied.
A customer is reporting difficulties, though details are quite sparse.
The first 3 patches are scaffolding to make the backport simpler.

[Impact]

CIFS reconnects fail.

[Test Plan]

A test kernel made available to Microsoft has been verified to fix the problem.

[Where problems could occur]

This could perturb CIFS connections in new and different ways.

[Other Info]

PPA: https://launchpad.net/~timg-tpi/+archive/ubuntu/cifs-reconnect-sf00309672