keep shadowed vfsmounts together

preparation to switching mnt_hash to hlist

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

1 files changed, 23 insertions, 9 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 3b648da55d87..9db3ce397a83 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -621,12 +621,20 @@ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
 struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
 {
         struct list_head *head = m_hash(mnt, dentry);
-        struct mount *p;
+        struct mount *p, *res = NULL;
 
-        list_for_each_entry_reverse(p, head, mnt_hash)
+        list_for_each_entry(p, head, mnt_hash)
                 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
-                        return p;
-        return NULL;
+                        goto found;
+        return res;
+found:
+        res = p;
+        list_for_each_entry_continue(p, head, mnt_hash) {
+                if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
+                        break;
+                res = p;
+        }
+        return res;
 }
 
 /*
@@ -769,14 +777,14 @@ static void attach_mnt(struct mount *mnt,
                         struct mountpoint *mp)
 {
         mnt_set_mountpoint(parent, mp, mnt);
-        list_add_tail(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
+        list_add(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
         list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
 }
 
 /*
  * vfsmount lock must be held for write
  */
-static void commit_tree(struct mount *mnt)
+static void commit_tree(struct mount *mnt, struct mount *shadows)
 {
         struct mount *parent = mnt->mnt_parent;
         struct mount *m;
@@ -791,7 +799,10 @@ static void commit_tree(struct mount *mnt)
 
         list_splice(&head, n->list.prev);
 
-        list_add_tail(&mnt->mnt_hash,
+        if (shadows)
+                list_add(&mnt->mnt_hash, &shadows->mnt_hash);
+        else
+                list_add(&mnt->mnt_hash,
                                 m_hash(&parent->mnt, mnt->mnt_mountpoint));
         list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
         touch_mnt_namespace(n);
@@ -1659,12 +1670,15 @@ static int attach_recursive_mnt(struct mount *source_mnt,
                 touch_mnt_namespace(source_mnt->mnt_ns);
         } else {
                 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
-                commit_tree(source_mnt);
+                commit_tree(source_mnt, NULL);
         }
 
         list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
+                struct mount *q;
                 list_del_init(&child->mnt_hash);
-                commit_tree(child);
+                q = __lookup_mnt_last(&child->mnt_parent->mnt,
+                                      child->mnt_mountpoint);
+                commit_tree(child, q);
         }
         unlock_mount_hash();