MFC r250443: Check the return value of sbuf_finish().


git-svn-id: svn://svn.freebsd.org/base/stable/9@250976 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
MFC r250505:
- Fix nullfs vnode reference leak in nullfs_reclaim_lowervp().  The
  null_hashget() obtains the reference on the nullfs vnode, which must
  be dropped.

- Fix a wart which existed from the introduction of the nullfs
  caching, do not unlock lower vnode in the nullfs_reclaim_lowervp().
  It should be innocent, but now it is also formally safe.  Inform the
  nullfs_reclaim() about this using the NULLV_NOUNLOCK flag set on
  nullfs inode.

- Add a callback to the upper filesystems for the lower vnode
  unlinking. When inactivating a nullfs vnode, check if the lower
  vnode was unlinked, indicated by nullfs flag NULLV_DROP or VV_NOSYNC
  on the lower vnode, and reclaim upper vnode if so.  This allows
  nullfs to purge cached vnodes for the unlinked lower vnode, avoiding
  excessive caching.

MFC r250852:
Do not leak the NULLV_NOUNLOCK flag from the nullfs_unlink_lowervp(),
for the case when the nullfs vnode is not reclaimed.  Otherwise, later
reclamation would not unlock the lower vnode.


git-svn-id: svn://svn.freebsd.org/base/stable/9@250978 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
MFC r250533:
	Unconditionally install 210.backup-aliases as many MTAs other than
	sendmail support the use of /etc/aliases.

PR:		conf/176098


git-svn-id: svn://svn.freebsd.org/base/stable/9@250983 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
MFC r250763 and r250765:
Fix some USB audio device issues.

PR:	usb/178722


git-svn-id: svn://svn.freebsd.org/base/stable/9@250987 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Merge remote-tracking branch 'upstream/svn_stable_9' into svn_stable_9