73 files changed, 773 insertions, 1080 deletions

diff --git a/Documentation/filesystems/sharedsubtree.txt b/Documentation/filesystems/sharedsubtree.txt
index 23a181074f94..fc0e39af43c3 100644
--- a/Documentation/filesystems/sharedsubtree.txt
+++ b/Documentation/filesystems/sharedsubtree.txt
@@ -837,6 +837,9 @@ replicas continue to be exactly same.
          individual lists does not affect propagation or the way propagation
          tree is modified by operations.
 
+        All vfsmounts in a peer group have the same ->mnt_master.  If it is
+        non-NULL, they form a contiguous (ordered) segment of slave list.
+
         A example propagation tree looks as shown in the figure below.
         [ NOTE: Though it looks like a forest, if we consider all the shared
         mounts as a conceptual entity called 'pnode', it becomes a tree]
@@ -874,8 +877,19 @@ replicas continue to be exactly same.
 
         NOTE: The propagation tree is orthogonal to the mount tree.
 
+8B Locking:
+
+        ->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected
+        by namespace_sem (exclusive for modifications, shared for reading).
+
+        Normally we have ->mnt_flags modifications serialized by vfsmount_lock.
+        There are two exceptions: do_add_mount() and clone_mnt().
+        The former modifies a vfsmount that has not been visible in any shared
+        data structures yet.
+        The latter holds namespace_sem and the only references to vfsmount
+        are in lists that can't be traversed without namespace_sem.
 
-8B Algorithm:
+8C Algorithm:
 
         The crux of the implementation resides in rbind/move operation.
 
diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index 341aff2687a5..cd128b07beda 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -288,46 +288,30 @@ static int hypfs_fill_super(struct super_block *sb, void *data, int silent)
         sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
         sb->s_magic = HYPFS_MAGIC;
         sb->s_op = &hypfs_s_ops;
-        if (hypfs_parse_options(data, sb)) {
-                rc = -EINVAL;
-                goto err_alloc;
-        }
+        if (hypfs_parse_options(data, sb))
+                return -EINVAL;
         root_inode = hypfs_make_inode(sb, S_IFDIR | 0755);
-        if (!root_inode) {
-                rc = -ENOMEM;
-                goto err_alloc;
-        }
+        if (!root_inode)
+                return -ENOMEM;
         root_inode->i_op = &simple_dir_inode_operations;
         root_inode->i_fop = &simple_dir_operations;
-        root_dentry = d_alloc_root(root_inode);
+        sb->s_root = root_dentry = d_alloc_root(root_inode);
         if (!root_dentry) {
                 iput(root_inode);
-                rc = -ENOMEM;
-                goto err_alloc;
+                return -ENOMEM;
         }
         if (MACHINE_IS_VM)
                 rc = hypfs_vm_create_files(sb, root_dentry);
         else
                 rc = hypfs_diag_create_files(sb, root_dentry);
         if (rc)
-                goto err_tree;
+                return rc;
         sbi->update_file = hypfs_create_update_file(sb, root_dentry);
-        if (IS_ERR(sbi->update_file)) {
-                rc = PTR_ERR(sbi->update_file);
-                goto err_tree;
+        if (IS_ERR(sbi->update_file))
+                return PTR_ERR(sbi->update_file);