[backport] linux 5.13 compat: bdevops->revalidate_disk() removed

[jonathonf]

Linux kernel commit 0f00b82e5413571ed225ddbccad6882d7ea60bc7 removes the
revalidate_disk() handler from struct block_device_operations. This
caused a regression, and this commit eliminates the call to it and the
assignment in the block_device_operations static handler assignment
code, when configure identifies that the kernel doesn't support that
API handler.

Reviewed-by: Colin Ian King colin.king@canonical.com
Reviewed-by: Brian Behlendorf behlendorf1@llnl.gov
Signed-off-by: Coleman Kane ckane@colemankane.org
Closes #11967
Closes #11977
(cherry picked from commit 48c7b0e)
Signed-off-by: Jonathon Fernyhough jonathon@m2x.dev

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.

[tonyhutter]

Just for quick reference, the only thing ZFS does in revalidate_disk() is set the capacity:

zvol_revalidate_disk(struct gendisk *disk)
{
...
                set_capacity(zv->zv_zso->zvo_disk,
...
}

That's appears to be unneeded in newer kernels:
https://patchwork.kernel.org/project/linux-block/patch/20210308074550.422714-3-hch@lst.de/

So once the checkstyle error is fixed it should be good to go.

[tonyhutter]

This looks good. The checkstyle error is unrelated to this patch.