Re: 2.6.0-test1: autofs4 doesn't expire

[spam@streefland.xs4all.nl (Dick Streefland)]

spam@streefland.xs4all.nl (Dick Streefland) wrote:
| In 2.6.0-test1, the autofs4 automounter doesn't expire mounts anymore,
| both NFS and CDROM mounts. It did work in my previous kernel, 2.5.72.
| When I try to unmount manually, I get "device is busy", although
| "fuser -m" doesn't report anything. I've also searched /proc/*/fd/,
| but there are no open files below the mount points.
| 
| Is anybody else seeing this? Any ideas what could be the cause?

Update: 2.5.75 is OK, so the problem was introduced in 2.6.0-test1.
I have not yet verified it, but I suspect that the addition of the
mntget() call is the cause:

==> fs/namespace.c <==
+/*
+ * Now, lookup_mnt increments the ref count before returning
+ * the vfsmount struct.
+ */
 struct vfsmount *lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
 {
 	struct list_head * head = mount_hashtable + hash(mnt, dentry);
 	struct list_head * tmp = head;
-	struct vfsmount *p;
+	struct vfsmount *p, *found = NULL;
 
+	spin_lock(&vfsmount_lock);
 	for (;;) {
 		tmp = tmp->next;
 		p = NULL;
 		if (tmp == head)
 			break;
 		p = list_entry(tmp, struct vfsmount, mnt_hash);
-		if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry)
+		if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
+			found = mntget(p);
 			break;
+		}
 	}
-	return p;
+	spin_unlock(&vfsmount_lock);
+	return found;
 }

-- 
Dick Streefland                    ////               De Bilt
dick.streefland@xs4all.nl         (@ @)       The Netherlands
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