Replace the MNT_VNODE_FOREACH interface with MNT_VNODE_FOREACH_ALL.

The primary changes are that the user of the interface no longer
needs to manage the mount-mutex locking and that the vnode that
is returned has its mutex locked (thus avoiding the need to check
to see if its is DOOMED or other possible end of life senarios).

To minimize compatibility issues for third-party developers, the
old MNT_VNODE_FOREACH interface will remain available so that this
change can be MFC'ed to 9. Following the MFC to 9, MNT_VNODE_FOREACH
will be removed in head.

The reason for this update is to prepare for the addition of the
MNT_VNODE_FOREACH_ACTIVE interface that will loop 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, 91 insertions, 18 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 051f8f7..14f8528 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -2467,17 +2467,13 @@ vflush(struct mount *mp, int rootrefs, int flags, struct thread *td)
 		}
 		vput(rootvp);
 	}
-	MNT_ILOCK(mp);
 loop:
-	MNT_VNODE_FOREACH(vp, mp, mvp) {
-		VI_LOCK(vp);
+	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
 		vholdl(vp);
-		MNT_IUNLOCK(mp);
 		error = vn_lock(vp, LK_INTERLOCK | LK_EXCLUSIVE);
 		if (error) {
 			vdrop(vp);
-			MNT_ILOCK(mp);
-			MNT_VNODE_FOREACH_ABORT_ILOCKED(mp, mvp);
+			MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
 			goto loop;
 		}
 		/*
@@ -2486,7 +2482,6 @@ loop:
 		if ((flags & SKIPSYSTEM) && (vp->v_vflag & VV_SYSTEM)) {
 			VOP_UNLOCK(vp, 0);
 			vdrop(vp);
-			MNT_ILOCK(mp);
 			continue;
 		}
 		/*
@@ -2504,7 +2499,7 @@ loop:
 			if (error != 0) {
 				VOP_UNLOCK(vp, 0);
 				vdrop(vp);
-				MNT_VNODE_FOREACH_ABORT(mp, mvp);
+				MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
 				return (error);
 			}
 			error = VOP_GETATTR(vp, &vattr, td->td_ucred);
@@ -2515,7 +2510,6 @@ loop:
 			    (vp->v_writecount == 0 || vp->v_type != VREG)) {
 				VOP_UNLOCK(vp, 0);
 				vdropl(vp);
-				MNT_ILOCK(mp);
 				continue;
 			}
 		} else
@@ -2540,9 +2534,7 @@ loop:
 		}
 		VOP_UNLOCK(vp, 0);
 		vdropl(vp);
-		MNT_ILOCK(mp);
 	}
-	MNT_IUNLOCK(mp);
 	if (rootrefs > 0 && (flags & FORCECLOSE) == 0) {
 		/*
 		 * If just the root vnode is busy, and if its refcount
@@ -3279,19 +3271,15 @@ vfs_msync(struct mount *mp, int flags)
 	struct vm_object *obj;
 
 	CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
-	MNT_ILOCK(mp);
-	MNT_VNODE_FOREACH(vp, mp, mvp) {
-		VI_LOCK(vp);
+	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
 		obj = vp->v_object;
 		if (obj != NULL && (obj->flags & OBJ_MIGHTBEDIRTY) != 0 &&
 		    (flags == MNT_WAIT || VOP_ISLOCKED(vp) == 0)) {
-			MNT_IUNLOCK(mp);
 			if (!vget(vp,
 			    LK_EXCLUSIVE | LK_RETRY | LK_INTERLOCK,
 			    curthread)) {
 				if (vp->v_vflag & VV_NOSYNC) {	/* unlinked */
 					vput(vp);
-					MNT_ILOCK(mp);
 					continue;
 				}
 
@@ -3305,11 +3293,9 @@ vfs_msync(struct mount *mp, int flags)
 				}
 				vput(vp);
 			}
-			MNT_ILOCK(mp);
 		} else
 			VI_UNLOCK(vp);
 	}
-	MNT_IUNLOCK(mp);
 }
 
 /*
@@ -4504,3 +4490,90 @@ vfs_unixify_accmode(accmode_t *accmode)
 
 	return (0);
 }
+
+/*
+ * These are helper functions for filesystems to traverse all
+ * their vnodes.  See MNT_VNODE_FOREACH_ALL() in sys/mount.h.
+ *
+ * This interface replaces MNT_VNODE_FOREACH.
+ */
+
+MALLOC_DEFINE(M_VNODE_MARKER, "vnodemarker", "vnode marker");
+
+struct vnode *
+__mnt_vnode_next_all(struct vnode **mvp, struct mount *mp)
+{
+	struct vnode *vp;
+
+	if (should_yield())
+		kern_yield(PRI_UNCHANGED);
+	MNT_ILOCK(mp);
+	KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
+	vp = TAILQ_NEXT(*mvp, v_nmntvnodes);
+	while (vp != NULL && (vp->v_type == VMARKER ||
+	    (vp->v_iflag & VI_DOOMED) != 0))
+		vp = TAILQ_NEXT(vp, v_nmntvnodes);
+
+	/* Check if we are done */
+	if (vp == NULL) {
+		__mnt_vnode_markerfree_all(mvp, mp);
+		/* MNT_IUNLOCK(mp); -- done in above function */
+		mtx_assert(MNT_MTX(mp), MA_NOTOWNED);
+		return (NULL);
+	}
+	TAILQ_REMOVE(&mp->mnt_nvnodelist, *mvp, v_nmntvnodes);
+	TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, *mvp, v_nmntvnodes);
+	VI_LOCK(vp);
+	MNT_IUNLOCK(mp);
+	return (vp);
+}
+
+struct vnode *
+__mnt_vnode_first_all(struct vnode **mvp, struct mount *mp)
+{
+	struct vnode *vp;
+
+	*mvp = malloc(sizeof(struct vnode), M_VNODE_MARKER, M_WAITOK | M_ZERO);
+	MNT_ILOCK(mp);
+	MNT_REF(mp);
+	(*mvp)->v_type = VMARKER;
+
+	vp = TAILQ_FIRST(&mp->mnt_nvnodelist);
+	while (vp != NULL && (vp->v_type == VMARKER ||
+	    (vp->v_iflag & VI_DOOMED) != 0))
+		vp = TAILQ_NEXT(vp, v_nmntvnodes);
+
+	/* Check if we are done */
+	if (vp == NULL) {
+		*mvp = NULL;
+		MNT_REL(mp);
+		MNT_IUNLOCK(mp);
+		free(*mvp, M_VNODE_MARKER);
+		return (NULL);
+	}
+	(*mvp)->v_mount = mp;
+	TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, *mvp, v_nmntvnodes);
+	VI_LOCK(vp);
+	MNT_IUNLOCK(mp);
+	return (vp);
+}
+
+
+void
+__mnt_vnode_markerfree_all(struct vnode **mvp, struct mount *mp)
+{
+
+	if (*mvp == NULL) {
+		MNT_IUNLOCK(mp);
+		return;
+	}
+
+	mtx_assert(MNT_MTX(mp), MA_OWNED);
+
+	KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
+	TAILQ_REMOVE(&mp->mnt_nvnodelist, *mvp, v_nmntvnodes);
+	MNT_REL(mp);
+	MNT_IUNLOCK(mp);
+	free(*mvp, M_VNODE_MARKER);
+	*mvp = NULL;
+}