MFC r328339:

Add SPDX tags to autofs(5).

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

Speed up lookups in autofs(5) by using red-black trees instead of linear
searches.

Reviewed by: kib@
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D5627

Remove name length limitation from autofs(5). The linear search with
strlens is somewhat suboptimal, but it's a temporary measure that will
be replaced with red-black trees later on.

PR: 204417
Reviewed by: kib@
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D5266

Implement "automount -c".

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make automountd(8) inform autofs(4) whether directory being handled can
have wildcards. This makes it possible for autofs(4) to avoid requesting
automountd(8) action on access to nonexistent nodes - unless wildcards
are actually used.

Note that this change breaks ABI for automountd(8).

Tested by: dhw@
MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make autofs use shared vnode locks.

Reviewed by: kib
MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Fix autofs debug macros.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make autofs(4) use shared lock for lookups, instead of exclusive one.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation

Make autofs timeout handling use timeout task instead of callout;
that's because the handler can sleep on sx lock.

Reviewed by: kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation

Autofs softc needs to be global anyway, so don't pass it as a local
variable, and don't store in autofs_mount. Also rename it from 'sc'
to 'autofs_softc', since it's global and extern.

MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation

Use __FBSDID() properly.

Suggested by: pluknet@
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation

Bring in the new automounter, similar to what's provided in most other
UNIX systems, eg. MacOS X and Solaris. It uses Sun-compatible map format,
has proper kernel support, and LDAP integration.

There are still a few outstanding problems; they will be fixed shortly.

Reviewed by: allanjude@, emaste@, kib@, wblock@ (earlier versions)
Phabric: D523
MFC after: 2 weeks
Relnotes: yes
Sponsored by: The FreeBSD Foundation