MFC r299412:
Add vfs_hash_ref(9) function, which finds a vnode by the hash value
and returns it referenced.

MFC r299408:
Style: wrap long lines.

The stable/10 branch uses mutex for vfs_hash. Fix build.

Submitted by: Jukka Ukkonen <jau789@gmail.com>

MFC of 281677:

More accurately collect name-cache statistics in sysctl functions
sysctl_debug_hashstat_nchash() and sysctl_debug_hashstat_rawnchash().
These changes are in preparation for allowing changes in the size
of the vnode hash tables driven by increases and decreases in the
maximum number of vnodes in the system.

Reviewed by: kib@
Phabric: D2265

MFC of 287497:

Track changes to kern.maxvnodes and appropriately increase or decrease
the size of the name cache hash table (mapping file names to vnodes)
and the vnode hash table (mapping mount point and inode number to vnode).
An appropriate locking strategy is the key to changing hash table sizes
while they are in active use.

Reviewed by: kib
Tested by: Peter Holm
Differential Revision: https://reviews.freebsd.org/D2265

The stable/10 branch uses mutex for vfs_hash. Fix build.

Submitted by: Jukka Ukkonen <jau789@gmail.com>

MFC of 281677:

More accurately collect name-cache statistics in sysctl functions
sysctl_debug_hashstat_nchash() and sysctl_debug_hashstat_rawnchash().
These changes are in preparation for allowing changes in the size
of the vnode hash tables driven by increases and decreases in the
maximum number of vnodes in the system.

Reviewed by: kib@
Phabric: D2265

MFC of 287497:

Track changes to kern.maxvnodes and appropriately increase or decrease
the size of the name cache hash table (mapping file names to vnodes)
and the vnode hash table (mapping mount point and inode number to vnode).
An appropriate locking strategy is the key to changing hash table sizes
while they are in active use.

Reviewed by: kib
Tested by: Peter Holm
Differential Revision: https://reviews.freebsd.org/D2265