[PATCH] mount expiry fixes

 - clean up the ugliness in may_umount_tree()

 - fix a bug in do_loopback().  after cloning a tree, do_loopback()
   unlinks only the topmost mount of the cloned tree, leaving behind the
   children mounts on their corresponding expiry list.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index c2ffa0f..65f9c0e 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -27,6 +27,8 @@
 
 extern int __init init_rootfs(void);
 
+#define CL_EXPIRE      0x01
+
 #ifdef CONFIG_SYSFS
 extern int __init sysfs_init(void);
 #else
@@ -165,7 +167,8 @@ static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *root)
        return list_entry(next, struct vfsmount, mnt_child);
 }
 
-static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root)
+static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
+                                       int flag)
 {
        struct super_block *sb = old->mnt_sb;
        struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
@@ -181,10 +184,12 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root)
 
                /* stick the duplicate mount on the same expiry list
                 * as the original if that was on one */
-               spin_lock(&vfsmount_lock);
-               if (!list_empty(&old->mnt_expire))
-                       list_add(&mnt->mnt_expire, &old->mnt_expire);
-               spin_unlock(&vfsmount_lock);
+               if (flag & CL_EXPIRE) {
+                       spin_lock(&vfsmount_lock);
+                       if (!list_empty(&old->mnt_expire))
+                               list_add(&mnt->mnt_expire, &old->mnt_expire);
+                       spin_unlock(&vfsmount_lock);
+               }
        }
        return mnt;
 }
@@ -331,36 +336,14 @@ struct seq_operations mounts_op = {
  */
 int may_umount_tree(struct vfsmount *mnt)
 {
-       struct list_head *next;
-       struct vfsmount *this_parent = mnt;
-       int actual_refs;
-       int minimum_refs;
+       int actual_refs = 0;
+       int minimum_refs = 0;
+       struct vfsmount *p;
 
        spin_lock(&vfsmount_lock);
-       actual_refs = atomic_read(&mnt->mnt_count);
-       minimum_refs = 2;
-repeat:
-       next = this_parent->mnt_mounts.next;
-resume:
-       while (next != &this_parent->mnt_mounts) {
-               struct vfsmount *p =
-                   list_entry(next, struct vfsmount, mnt_child);
-
-               next = next->next;
-
+       for (p = mnt; p; p = next_mnt(p, mnt)) {
                actual_refs += atomic_read(&p->mnt_count);
                minimum_refs += 2;
-
-               if (!list_empty(&p->mnt_mounts)) {
-                       this_parent = p;
-                       goto repeat;
-               }
-       }
-
-       if (this_parent != mnt) {
-               next = this_parent->mnt_child.next;
-               this_parent = this_parent->mnt_parent;
-               goto resume;
        }
        spin_unlock(&vfsmount_lock);
 
@@ -596,12 +579,13 @@ static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
        }
 }
 
-static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry)
+static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
+                                       int flag)
 {
        struct vfsmount *res, *p, *q, *r, *s;
        struct nameidata nd;
 
-       res = q = clone_mnt(mnt, dentry);
+       res = q = clone_mnt(mnt, dentry, flag);
        if (!q)
                goto Enomem;
        q->mnt_mountpoint = mnt->mnt_mountpoint;
@@ -619,7 +603,7 @@ static struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry)
                        p = s;
                        nd.mnt = q;
                        nd.dentry = p->mnt_mountpoint;
-                       q = clone_mnt(p, p->mnt_root);
+                       q = clone_mnt(p, p->mnt_root, flag);
                        if (!q)
                                goto Enomem;
                        spin_lock(&vfsmount_lock);
@@ -701,18 +685,13 @@ static int do_loopback(struct nameidata *nd, char *old_name, int recurse)
 
        err = -ENOMEM;
        if (recurse)
-               mnt = copy_tree(old_nd.mnt, old_nd.dentry);
+               mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0);
        else
-               mnt = clone_mnt(old_nd.mnt, old_nd.dentry);
+               mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0);
 
        if (!mnt)
                goto out;
 
-       /* stop bind mounts from expiring */
-       spin_lock(&vfsmount_lock);
-       list_del_init(&mnt->mnt_expire);
-       spin_unlock(&vfsmount_lock);
-
        err = graft_tree(mnt, nd);
        if (err) {
                LIST_HEAD(umount_list);
@@ -1155,7 +1134,8 @@ int copy_namespace(int flags, struct task_struct *tsk)
 
        down_write(&tsk->namespace->sem);
        /* First pass: copy the tree topology */
-       new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root);
+       new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root,
+                                       CL_EXPIRE);
        if (!new_ns->root) {
                up_write(&tsk->namespace->sem);
                kfree(new_ns);