MFC 324073: Use UMA_ALIGNOF() for name cache UMA zones.

This fixes kernel crashes due to misaligned accesses to the 64-bit
time_t embedded in struct namecache_ts in MIPS n32 kernels.

MFC r281829 (by trasz@):

Modify kern___getcwd() to take max pathlen limit as an additional
argument. This will be used for the Linux emulation layer - for Linux,
PATH_MAX is 4096 and not 1024.

MFC r293295:

cache: ansify functions and fix some style issues

No functional changes.

MFC r292384:

Fix style issues around existing SDT probes.

** Changes to sys/netinet/in_kdtrace.c and sys/netinet/in_kdtrace.h skipped.

MFC r298819:

sys/kern: spelling fixes in comments.

MFC r288336: save some bytes by using more concise SDT_PROBE<n>

Fix build with options DIAGNOSTIC.

Sponsored by: EMC / Isilon storage division
In collaboration with: kib

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

MFC r276564, r276654:

Cast *path to silence clang -Wpointer-sign warning.

Indeed, instead of hiding the kern___getcwd() bug by bogus cast
in r276564, change path type to char * (pathnames are always char *).
And remove bogus casts of malloc().
kern___getcwd() internally doesn't actually use or support u_char *
paths, except to copy them to a normal char * path.

These changes are not visible to libc as libc/gen/getcwd.c misdeclares
__getcwd() as taking a plain char * path.

While here remove _SYS_SYSPROTO_H_ for __getcwd() syscall as
we always have sysproto.h.

MFC r263710, r273377, r273378, r273423 and r273455:

- De-vnet hash sizes and hash masks.
- Fix multiple issues related to arguments passed to SYSCTL macros.

Sponsored by: Mellanox Technologies

MFC r258622: dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE

MFC r259953:
Fix accounting for the negative cache entries when reusing v_cache_dd.

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

MFC r276564, r276654:

Cast *path to silence clang -Wpointer-sign warning.

Indeed, instead of hiding the kern___getcwd() bug by bogus cast
in r276564, change path type to char * (pathnames are always char *).
And remove bogus casts of malloc().
kern___getcwd() internally doesn't actually use or support u_char *
paths, except to copy them to a normal char * path.

These changes are not visible to libc as libc/gen/getcwd.c misdeclares
__getcwd() as taking a plain char * path.

While here remove _SYS_SYSPROTO_H_ for __getcwd() syscall as
we always have sysproto.h.

MFC r263710, r273377, r273378, r273423 and r273455:

- De-vnet hash sizes and hash masks.
- Fix multiple issues related to arguments passed to SYSCTL macros.

Sponsored by: Mellanox Technologies

MFC r258622: dtrace sdt: remove the ugly sname parameter of SDT_PROBE_DEFINE

MFC r259953:
Fix accounting for the negative cache entries when reusing v_cache_dd.