Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

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

The function is similar to vfs_hash_get(9), but unlike the later,
returned vnode is not locked. This operation cannot be requested with
the vget(9) flags.

Reviewed and tested by: rmacklem
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

Style: wrap long lines.

Sponsored by: The FreeBSD Foundation
MFC after: 1 week

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 after: 2 weeks

vfs: implement v_holdcnt/v_usecount manipulation using atomic ops

Transitions 0->1 and 1->0 (which decide e.g. on putting the vnode on the free
list) of either counter are still guarded with vnode interlock.

Reviewed by: kib (earlier version)
Tested by: pho

Convert vfs hash lock from a mutex to an rwlock.

Add exported vfs_hash_index() function, which calculates the canonical
pre-masked hash for the given vnode. The function assumes that
vp->v_hash is initialized by the filesystem vnode instantiation
function. At the moment, it is only done if filesystem uses
vfs_hash_insert().

Reviewed by: peter
Tested by: peter, pho (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 5 days

Rename vfs_hash_index() to vfs_hash_bucket().

Reviewed by: peter
Tested by: peter, pho
Sponsored by: The FreeBSD Foundation
MFC after: 5 days

In keeping with style(9)'s recommendations on macros, use a ';'
after each SYSINIT() macro invocation. This makes a number of
lightweight C parsers much happier with the FreeBSD kernel
source, including cflow's prcc and lxr.

MFC after: 1 month
Discussed with: imp, rink

Make insmntque() externally visibile and allow it to fail (e.g. during
late stages of unmount). On failure, the vnode is recycled.

Add insmntque1(), to allow for file system specific cleanup when
recycling vnode on failure.

Change getnewvnode() to no longer call insmntque(). Previously,
embryonic vnodes were put onto the list of vnode belonging to a file
system, which is unsafe for a file system marked MPSAFE.

Change vfs_hash_insert() to no longer lock the vnode. The caller now
has that responsibility.

Change most file systems to lock the vnode and call insmntque() or
insmntque1() after a new vnode has been sufficiently setup. Handle
failed insmntque*() calls by propagating errors to callers, possibly
after some file system specific cleanup.

Approved by: re (kensmith)
Reviewed by: kib
In collaboration with: kib

In vfs_hash_get(): mount point should never be changed
so explicitly constify the mp parameter.

Reviewed by: phk

Normalize a significant number of kernel malloc type names:

- Prefer '_' to ' ', as it results in more easily parsed results in
memory monitoring tools such as vmstat.

- Remove punctuation that is incompatible with using memory type names
as file names, such as '/' characters.

- Disambiguate some collisions by adding subsystem prefixes to some
memory types.

- Generally prefer lower case to upper case.

- If the same type is defined in multiple architecture directories,
attempt to use the same name in additional cases.

Not all instances were caught in this change, so more work is required to
finish this conversion. Similar changes are required for UMA zone names.

Don't retry when vget() returns ENOENT in the nonblocking case due to the
vnode being doomed. It causes a livelock.

Fix bug in vfs_hash_rehash(): use correct bucket. This only affected
msdosfs which is broken in other ways too.

- Grab the lock type that the caller requests in vfs_hash_insert().

Sponsored by: Isilon Systems, Inc.

Fix a bad copy&paste mistake I made.

Spotted by: truckman

Add two arguments to the vfs_hash() KPI so that filesystems which do
not have unique hashes (NFS) can also use it.

Add mnt_hashseed to struct mount and initialize it witn PRNG bits, use
it to get better hashing in vfs_hash.

In case of an insert collision in vfs_hash_insert(), put the loosing vnode
on a special list so that vfs_hash_remove() can just assume that it is on
a list.

Drop the VI_HASHED flag.

Improve the vfs_hash() API: vput() the unneeded vnode centrally to
avoid replicating the vput in all the filesystems.

Simplify the vfs_hash calling convention.

Cleanup accidentally include #if 0 section.

Currently (almost) all filesystems maintain a local inode hash table
to get from (mount + inode) to vnode. These tables are mostly
copy&pasted from UFS, sized based on desiredvnodes and therefore
quite large (128K-512K). Several filesystems are buggy enough that
they allocate the hash table even before they know if they will
ever be used or not.

Add "vfs_hash", a system wide hash table, which will replace all
the per-filesystem hash-tables.

The fields we add to struct vnode will more or less be saved in
the respective filesystems inodes.

Having one central implementation will save code and will allow us
to justify the complexity of code to dynamically (re)size the hash
at a later point.