mount: add vnode usage per file system with mount -v

This avoids the need to drop into the ddb to figure out vnode
usage per file system.  It helps to see if they are or are not
being freed.  Suggestion to report active vnode count was from
kib@

Reviewed by:   	kib
Differential Revision: https://reviews.freebsd.org/D35436

3 files changed, 22 insertions, 1 deletions

diff --git a/sbin/mount/mount.c b/sbin/mount/mount.c
index 79d9d6cb0caf..bd3d0073c474 100644
--- a/sbin/mount/mount.c
+++ b/sbin/mount/mount.c
@@ -692,6 +692,13 @@ prmount(struct statfs *sfp)
 			xo_emit("{D:, }{Lw:fsid}{:fsid}", fsidbuf);
 			free(fsidbuf);
 		}
+		if (sfp->f_nvnodelistsize != 0 || sfp->f_avnodecount != 0) {
+			xo_open_container("vnodes");
+			xo_emit("{D:, }{Lwc:vnodes}{Lw:count}{w:count/%ju}{Lw:active}{:active/%ju}",
+			    (uintmax_t)sfp->f_nvnodelistsize,
+			    (uintmax_t)sfp->f_avnodecount);
+			xo_close_container("vnodes");
+		}
 	}
 	xo_emit("{D:)}\n");
 }
diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 71a40fd97a9c..e3818b67e841 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -2610,6 +2610,8 @@ vfs_copyopt(struct vfsoptlist *opts, const char *name, void *dest, int len)
 int
 __vfs_statfs(struct mount *mp, struct statfs *sbp)
 {
+	struct vnode *vp;
+	uint32_t count;
 
 	/*
 	 * Filesystems only fill in part of the structure for updates, we
@@ -2624,6 +2626,16 @@ __vfs_statfs(struct mount *mp, struct statfs *sbp)
 	sbp->f_version = STATFS_VERSION;
 	sbp->f_namemax = NAME_MAX;
 	sbp->f_flags = mp->mnt_flag & MNT_VISFLAGMASK;
+	sbp->f_nvnodelistsize = mp->mnt_nvnodelistsize;
+
+	count = 0;
+	MNT_ILOCK(mp);
+	TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
+		if (vrefcnt(vp) > 0) /* racy but does not matter */
+			count++;
+	}
+	MNT_IUNLOCK(mp);
+	sbp->f_avnodecount = count;
 
 	return (mp->mnt_op->vfs_statfs(mp, sbp));
 }
diff --git a/sys/sys/mount.h b/sys/sys/mount.h
index 3383bfe8f431..edac64171f9a 100644
--- a/sys/sys/mount.h
+++ b/sys/sys/mount.h
@@ -91,7 +91,9 @@ struct statfs {
 	uint64_t f_asyncwrites;		/* count of async writes since mount */
 	uint64_t f_syncreads;		/* count of sync reads since mount */
 	uint64_t f_asyncreads;		/* count of async reads since mount */
-	uint64_t f_spare[10];		/* unused spare */
+	uint32_t f_nvnodelistsize;	/* # of vnodes */
+	uint32_t f_avnodecount;		/* # of active vnodes */
+	uint64_t f_spare[9];		/* unused spare */
 	uint32_t f_namemax;		/* maximum filename length */
 	uid_t	  f_owner;		/* user that mounted the filesystem */
 	fsid_t	  f_fsid;		/* filesystem id */