From 7c4b93d8269b9d35971a8239426b1f6ddc3d5ef7 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Fri, 21 Mar 2008 23:59:49 -0400
Subject: [PATCH] count ghost references to vfsmounts

make propagate_mount_busy() exclude references from the vfsmounts
that had been isolated by umount_tree() and are just waiting for
release_mounts() to dispose of their ->mnt_parent/->mnt_mountpoint.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namespace.c b/fs/namespace.c
index 6324dfc..c175218 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -548,6 +548,7 @@ void release_mounts(struct list_head *head)
 			m = mnt->mnt_parent;
 			mnt->mnt_mountpoint = mnt->mnt_root;
 			mnt->mnt_parent = mnt;
+			m->mnt_ghosts--;
 			spin_unlock(&vfsmount_lock);
 			dput(dentry);
 			mntput(m);
@@ -572,8 +573,10 @@ void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
 		__touch_mnt_namespace(p->mnt_ns);
 		p->mnt_ns = NULL;
 		list_del_init(&p->mnt_child);
-		if (p->mnt_parent != p)
+		if (p->mnt_parent != p) {
+			p->mnt_parent->mnt_ghosts++;
 			p->mnt_mountpoint->d_mounted--;
+		}
 		change_mnt_propagation(p, MS_PRIVATE);
 	}
 }
diff --git a/fs/pnode.c b/fs/pnode.c
index 05ba692..1d8f544 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -225,7 +225,7 @@ out:
  */
 static inline int do_refcount_check(struct vfsmount *mnt, int count)
 {
-	int mycount = atomic_read(&mnt->mnt_count);
+	int mycount = atomic_read(&mnt->mnt_count) - mnt->mnt_ghosts;
 	return (mycount > count);
 }
 
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 6d3047d..dac5e67 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -61,6 +61,7 @@ struct vfsmount {
 	atomic_t mnt_count;
 	int mnt_expiry_mark;		/* true if marked for expiry */
 	int mnt_pinned;
+	int mnt_ghosts;
 };
 
 static inline struct vfsmount *mntget(struct vfsmount *mnt)
-- 
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