ffs: retire unused fsckpid mount option

[rew]

Summary

The fsckpid mount option was introduced in 927a12ae16433b50 along with a
couple sysctl's to support SU+J with snapshots. However, those sysctl's
were never used and eventually removed in f2620e9ceb3ede02.

There are no in-tree consumers of this mount option.

[mckusick]

This change is a useful cleanup. To be complete you need to delete um_fsckpid from the ufsmount structure and its use in ffs_alloc.c and ffs_inode.c.

[mckusick]

Just saw that you made my requested change in https://reviews.freebsd.org/D32017.

[rew]

In D32015#722569, @mckusick wrote:

Just saw that you made my requested change in https://reviews.freebsd.org/D32017.

If there's no objections, I'll squash these two revisions into a single commit.

[mckusick]

In D32015#723182, @rew wrote:

In D32015#722569, @mckusick wrote:

Just saw that you made my requested change in https://reviews.freebsd.org/D32017.

If there's no objections, I'll squash these two revisions into a single commit.

I think a single commit is appropriate since they collectively represent a single cleanup. Kostik does like to break commits down into smaller pieces which is a policy that I generally like, but seems unnecessary here. But I would like to hear his opinion.

[kib]

In D32015#723613, @mckusick wrote:

In D32015#723182, @rew wrote:

In D32015#722569, @mckusick wrote:

Just saw that you made my requested change in https://reviews.freebsd.org/D32017.

If there's no objections, I'll squash these two revisions into a single commit.

I think a single commit is appropriate since they collectively represent a single cleanup. Kostik does like to break commits down into smaller pieces which is a policy that I generally like, but seems unnecessary here. But I would like to hear his opinion.

Smaller commits are easier for reader to grasp, and provide less content to ponder when bisect points to it. In this case, it does not matter, I am fine with either split or squash.