This change creates a new list of active vnodes associated with

a mount point. Active vnodes are those with a non-zero use or hold
count, e.g., those vnodes that are not on the free list. Note that
this list is in addition to the list of all the vnodes associated
with a mount point.

To avoid adding another set of linkage pointers to the vnode
structure, the active list uses the existing linkage pointers
used by the free list (previously named v_freelist, now renamed
v_actfreelist).

This update adds the MNT_VNODE_FOREACH_ACTIVE interface that loops
over just the active vnodes associated with a mount point (typically
less than 1% of the vnodes associated with the mount point).

Reviewed by: kib
Tested by:   Peter Holm
MFC after:   2 weeks

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 6a5dfb0..e9d3abe 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -461,6 +461,8 @@ vfs_mount_alloc(struct vnode *vp, struct vfsconf *vfsp, const char *fspath,
 	    __rangeof(struct mount, mnt_startzero, mnt_endzero));
 	TAILQ_INIT(&mp->mnt_nvnodelist);
 	mp->mnt_nvnodelistsize = 0;
+	TAILQ_INIT(&mp->mnt_activevnodelist);
+	mp->mnt_activevnodelistsize = 0;
 	mp->mnt_ref = 0;
 	(void) vfs_busy(mp, MBF_NOWAIT);
 	mp->mnt_op = vfsp->vfc_vfsops;
@@ -514,6 +516,8 @@ vfs_mount_destroy(struct mount *mp)
 	}
 	if (mp->mnt_nvnodelistsize != 0)
 		panic("vfs_mount_destroy: nonzero nvnodelistsize");
+	if (mp->mnt_activevnodelistsize != 0)
+		panic("vfs_mount_destroy: nonzero activevnodelistsize");
 	if (mp->mnt_lockref != 0)
 		panic("vfs_mount_destroy: nonzero lock refcount");
 	MNT_IUNLOCK(mp);