drainvnodes

Remove the "target" argment from vfs_drainvnodes() as it is
always equal to "desiredvnodes" and move its definition
from sys/vnode.h to sys/vnode_impl.h.

Extend vfs_drainvnodes() to also wait for deferred vrele to flush
and replace the call to vrele_flush() with a call to vfs_drainvnodes().

diff -r 26e77f76c704 -r 4091fa48cd30 sys/kern/init_sysctl.c
--- a/sys/kern/init_sysctl.c	Fri Dec 09 10:58:16 2016 +0100
+++ b/sys/kern/init_sysctl.c	Fri Dec 09 10:58:19 2016 +0100
@@ -47,7 +47,7 @@
 #include <sys/unistd.h>
 #include <sys/disklabel.h>
 #include <sys/cprng.h>
-#include <sys/vnode.h>
+#include <sys/vnode_impl.h>	/* For vfs_drainvnodes(). */
 #include <sys/mount.h>
 #include <sys/namei.h>
 #include <dev/cons.h>
@@ -756,7 +756,7 @@
 
 	old_vnodes = desiredvnodes;
 	desiredvnodes = new_vnodes;
-	error = vfs_drainvnodes(new_vnodes);
+	error = vfs_drainvnodes();
 	if (error) {
 		desiredvnodes = old_vnodes;
 		return (error);
diff -r 26e77f76c704 -r 4091fa48cd30 sys/kern/vfs_mount.c
--- a/sys/kern/vfs_mount.c	Fri Dec 09 10:58:16 2016 +0100
+++ b/sys/kern/vfs_mount.c	Fri Dec 09 10:58:19 2016 +0100
@@ -509,8 +509,8 @@
 	int error, busy = 0, when = 0;
 	struct vflush_ctx ctx;
 
-	/* First, flush out any vnode references from vrele_list. */
-	vrele_flush();
+	/* First, flush out any vnode references from deferred vrele list. */
+	vfs_drainvnodes();
 
 	vfs_vnode_iterator_init(mp, &marker);
 
diff -r 26e77f76c704 -r 4091fa48cd30 sys/kern/vfs_vnode.c
--- a/sys/kern/vfs_vnode.c	Fri Dec 09 10:58:16 2016 +0100
+++ b/sys/kern/vfs_vnode.c	Fri Dec 09 10:58:19 2016 +0100
@@ -208,6 +208,7 @@
 static struct {
 	kmutex_t	lock;
 	kcondvar_t	cv;
+	u_int		hashsize;
 	u_long		hashmask;
 	struct hashhead	*hashtab;
 	pool_cache_t	pool;
@@ -857,20 +858,6 @@
 	}
 }
 
-void
-vrele_flush(void)
-{
-	int gen;
-
-	mutex_enter(&vrele_lock);
-	gen = vrele_gen;
-	while (vrele_pending && gen == vrele_gen) {
-		cv_broadcast(&vrele_cv);
-		cv_wait(&vrele_cv, &vrele_lock);
-	}
-	mutex_exit(&vrele_lock);
-}
-
 /*
  * Vnode reference, where a reference is already held by some other
  * object (for example, a file structure).
@@ -1040,6 +1027,7 @@
 	KASSERT(vcache.pool != NULL);
 	mutex_init(&vcache.lock, MUTEX_DEFAULT, IPL_NONE);
 	cv_init(&vcache.cv, "vcache");
+	vcache.hashsize = desiredvnodes;
 	vcache.hashtab = hashinit(desiredvnodes, HASH_SLIST, true,
 	    &vcache.hashmask);
 }
@@ -1057,6 +1045,7 @@
 	mutex_enter(&vcache.lock);
 	oldtab = vcache.hashtab;
 	oldmask = vcache.hashmask;
+	vcache.hashsize = desiredvnodes;
 	vcache.hashtab = newtab;
 	vcache.hashmask = newmask;
 	for (i = 0; i <= oldmask; i++) {
@@ -1601,13 +1590,21 @@
 }
 
 int
-vfs_drainvnodes(long target)
+vfs_drainvnodes(void)
 {
-	int error;
+	int error, gen;
+
+	mutex_enter(&vrele_lock);
+	gen = vrele_gen;
+	while (vrele_pending && gen == vrele_gen) {
+		cv_broadcast(&vrele_cv);
+		cv_wait(&vrele_cv, &vrele_lock);
+	}
+	mutex_exit(&vrele_lock);
 
 	mutex_enter(&vnode_free_list_lock);
 
-	while (numvnodes > target) {
+	while (numvnodes > desiredvnodes) {
 		error = cleanvnode();
 		if (error != 0)
 			return error;
@@ -1616,7 +1613,8 @@
 
 	mutex_exit(&vnode_free_list_lock);
 
-	vcache_reinit();
+	if (vcache.hashsize != desiredvnodes)
+		vcache_reinit();
 
 	return 0;
 }
diff -r 26e77f76c704 -r 4091fa48cd30 sys/sys/vnode.h
--- a/sys/sys/vnode.h	Fri Dec 09 10:58:16 2016 +0100
+++ b/sys/sys/vnode.h	Fri Dec 09 10:58:19 2016 +0100
@@ -530,7 +530,6 @@
 bool	vrecycle(struct vnode *);
 void 	vrele(struct vnode *);
 void 	vrele_async(struct vnode *);
-void	vrele_flush(void);
 int	vtruncbuf(struct vnode *, daddr_t, bool, int);
 void	vwakeup(struct buf *);
 int	vdead_check(struct vnode *, int);
@@ -581,7 +580,6 @@
 
 /* see vfssubr(9) */
 void	vfs_getnewfsid(struct mount *);
-int	vfs_drainvnodes(long);
 void	vfs_timestamp(struct timespec *);
 #if defined(DDB) || defined(DEBUGPRINT)
 void	vfs_vnode_print(struct vnode *, int, void (*)(const char *, ...)
diff -r 26e77f76c704 -r 4091fa48cd30 sys/sys/vnode_impl.h
--- a/sys/sys/vnode_impl.h	Fri Dec 09 10:58:16 2016 +0100
+++ b/sys/sys/vnode_impl.h	Fri Dec 09 10:58:19 2016 +0100
@@ -67,5 +67,6 @@
 	vnalloc_marker(struct mount *);
 void	vnfree_marker(vnode_t *);
 bool	vnis_marker(vnode_t *);
+int	vfs_drainvnodes(void);
 
 #endif /* !_SYS_VNODE_IMPL_H_ */