Linux 5.13 compat: block device revalidate_disk removal

[ColinIanKing]

Linux 5.13 finally removed the block device revalidate_disk()
in 0f00b82e5413571ed225ddbccad6882d7ea60bc7 ("block: remove the
revalidate_disk method"). Add a build time check for this and
don't use it for kernels that don't support this unused API.

Signed-off-by: Colin Ian King [email protected]

Motivation and Context

Description

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.

[behlendorf]

@ColinIanKing thanks for the compatibility patch. There's actually an existing PR open, #11977, with an almost identical change which is ready to merge. Sorry we didn't get it merged a little sooner to spare you the trouble, but since you're already familiar with the upstream code change it would be great if you could review the other PR. Then we can merge it right away.

[behlendorf]

Closing, addressed by #11977.