VFS: remove MNTK_MARKER

We no longer allow upper filesystems to be unregistered from the base
mount while vfs_notify_upper() or any other upper operation is pending.
New upper mounts can still be registered during this period, but they
will be added at the end of the upper mount tailq.  We therefore no
longer need to allocate marker nodes during vfs_notify_upper() to keep
our place in the iteration.

Reviewed by:	kib, mckusick
Tested by:	pho
Differential Revision:	https://reviews.freebsd.org/D31016

1 files changed, 2 insertions, 32 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index 8add6951645f..23f6ec9cf3fd 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -3891,52 +3891,26 @@ vgone(struct vnode *vp)
 	VI_UNLOCK(vp);
 }
 
-static void
-notify_lowervp_vfs_dummy(struct mount *mp __unused,
-    struct vnode *lowervp __unused)
-{
-}
-
-struct notify_mount {
-	struct mount mp;
-	struct mount_upper_node upper;
-};
-
 /*
  * Notify upper mounts about reclaimed or unlinked vnode.
  */
 void
 vfs_notify_upper(struct vnode *vp, int event)
 {
-	static struct vfsops vgonel_vfsops = {
-		.vfs_reclaim_lowervp = notify_lowervp_vfs_dummy,
-		.vfs_unlink_lowervp = notify_lowervp_vfs_dummy,
-	};
 	struct mount *mp;
 	struct mount_upper_node *ump;
-	struct notify_mount *mmp;
 
-	mp = vp->v_mount;
+	mp = atomic_load_ptr(&vp->v_mount);
 	if (mp == NULL)
 		return;
 	if (TAILQ_EMPTY(&mp->mnt_notify))
 		return;
 
-	mmp = malloc(sizeof(*mmp), M_TEMP, M_WAITOK | M_ZERO);
-	mmp->mp.mnt_op = &vgonel_vfsops;
-	mmp->mp.mnt_kern_flag |= MNTK_MARKER;
-	mmp->upper.mp = &mmp->mp;
 	MNT_ILOCK(mp);
 	mp->mnt_upper_pending++;
 	KASSERT(mp->mnt_upper_pending > 0,
 	    ("%s: mnt_upper_pending %d", __func__, mp->mnt_upper_pending));
-	for (ump = TAILQ_FIRST(&mp->mnt_notify); ump != NULL;) {
-		if ((ump->mp->mnt_kern_flag & MNTK_MARKER) != 0) {
-			ump = TAILQ_NEXT(ump, mnt_upper_link);
-			continue;
-		}
-		TAILQ_INSERT_AFTER(&mp->mnt_notify, ump, &mmp->upper,
-		    mnt_upper_link);
+	TAILQ_FOREACH(ump, &mp->mnt_notify, mnt_upper_link) {
 		MNT_IUNLOCK(mp);
 		switch (event) {
 		case VFS_NOTIFY_UPPER_RECLAIM:
@@ -3950,10 +3924,7 @@ vfs_notify_upper(struct vnode *vp, int event)
 			break;
 		}
 		MNT_ILOCK(mp);
-		ump = TAILQ_NEXT(&mmp->upper, mnt_upper_link);
-		TAILQ_REMOVE(&mp->mnt_notify, &mmp->upper, mnt_upper_link);
 	}
-	free(mmp, M_TEMP);
 	mp->mnt_upper_pending--;
 	if ((mp->mnt_kern_flag & MNTK_UPPER_WAITER) != 0 &&
 	    mp->mnt_upper_pending == 0) {
@@ -4391,7 +4362,6 @@ DB_SHOW_COMMAND(mount, db_show_mount)
 	MNT_KERN_FLAG(MNTK_RECURSE);
 	MNT_KERN_FLAG(MNTK_UPPER_WAITER);
 	MNT_KERN_FLAG(MNTK_LOOKUP_EXCL_DOTDOT);
-	MNT_KERN_FLAG(MNTK_MARKER);
 	MNT_KERN_FLAG(MNTK_USES_BCACHE);
 	MNT_KERN_FLAG(MNTK_FPLOOKUP);
 	MNT_KERN_FLAG(MNTK_TASKQUEUE_WAITER);