[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>

1 files changed, 22 insertions, 42 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index c2ffa0f349fd..65f9c0ecc21c 100644
--- 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);