mnt: In umount_tree reuse mnt_list instead of mnt_hash

commit c003b26ff98ca04a180ff34c38c007a3998d62f9 upstream.

umount_tree builds a list of mounts that need to be unmounted.
Utilize mnt_list for this purpose instead of mnt_hash.  This begins to
allow keeping a mount on the mnt_hash after it is unmounted, which is
necessary for a properly functioning MNT_LOCKED implementation.

The fact that mnt_list is an ordinary list makding available list_move
is nice bonus.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 616a694..18df0af 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1329,23 +1329,25 @@ enum umount_tree_flags {
  */
 static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
 {
-       HLIST_HEAD(tmp_list);
+       LIST_HEAD(tmp_list);
        struct mount *p;
 
-       for (p = mnt; p; p = next_mnt(p, mnt)) {
-               hlist_del_init_rcu(&p->mnt_hash);
-               hlist_add_head(&p->mnt_hash, &tmp_list);
-       }
+       /* Gather the mounts to umount */
+       for (p = mnt; p; p = next_mnt(p, mnt))
+               list_move(&p->mnt_list, &tmp_list);
 
-       hlist_for_each_entry(p, &tmp_list, mnt_hash)
+       /* Hide the mounts from lookup_mnt and mnt_mounts */
+       list_for_each_entry(p, &tmp_list, mnt_list) {
+               hlist_del_init_rcu(&p->mnt_hash);
                list_del_init(&p->mnt_child);
+       }
 
+       /* Add propogated mounts to the tmp_list */
        if (how & UMOUNT_PROPAGATE)
                propagate_umount(&tmp_list);
 
-       while (!hlist_empty(&tmp_list)) {
-               p = hlist_entry(tmp_list.first, struct mount, mnt_hash);
-               hlist_del_init_rcu(&p->mnt_hash);
+       while (!list_empty(&tmp_list)) {
+               p = list_first_entry(&tmp_list, struct mount, mnt_list);
                list_del_init(&p->mnt_expire);
                list_del_init(&p->mnt_list);
                __touch_mnt_namespace(p->mnt_ns);

diff --git a/fs/pnode.c b/fs/pnode.c
index 260ac8f..bf012af 100644 (file)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -384,7 +384,7 @@ static void __propagate_umount(struct mount *mnt)
                if (child && list_empty(&child->mnt_mounts)) {
                        list_del_init(&child->mnt_child);
                        hlist_del_init_rcu(&child->mnt_hash);
-                       hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
+                       list_move_tail(&child->mnt_list, &mnt->mnt_list);
                }
        }
 }
@@ -396,11 +396,11 @@ static void __propagate_umount(struct mount *mnt)
  *
  * vfsmount lock must be held for write
  */
-int propagate_umount(struct hlist_head *list)
+int propagate_umount(struct list_head *list)
 {
        struct mount *mnt;
 
-       hlist_for_each_entry(mnt, list, mnt_hash)
+       list_for_each_entry(mnt, list, mnt_list)
                __propagate_umount(mnt);
        return 0;
 }

diff --git a/fs/pnode.h b/fs/pnode.h
index 16afc3d..aa6d65d 100644 (file)
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -40,7 +40,7 @@ static inline void set_mnt_shared(struct mount *mnt)
 void change_mnt_propagation(struct mount *, int);
 int propagate_mnt(struct mount *, struct mountpoint *, struct mount *,
                struct hlist_head *);
-int propagate_umount(struct hlist_head *);
+int propagate_umount(struct list_head *);
 int propagate_mount_busy(struct mount *, int);
 void mnt_release_group_id(struct mount *);
 int get_dominating_id(struct mount *mnt, const struct path *root);