Btrfs: Give each subvol and snapshot their own anonymous devid

Each subvolume has its own private inode number space, and so we need
to fill in different device numbers for each subvolume to avoid confusing
applications.

This commit puts a struct super_block into struct btrfs_root so it can
call set_anon_super() and get a different device number generated for
each root.

btrfs_rename is changed to prevent renames across subvols.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 0a53505..8d7866b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -877,6 +877,12 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
 	root->defrag_running = 0;
 	root->defrag_level = 0;
 	root->root_key.objectid = objectid;
+	root->anon_super.s_root = NULL;
+	root->anon_super.s_dev = 0;
+	INIT_LIST_HEAD(&root->anon_super.s_list);
+	INIT_LIST_HEAD(&root->anon_super.s_instances);
+	init_rwsem(&root->anon_super.s_umount);
+
 	return 0;
 }
 
@@ -1083,6 +1089,9 @@ struct btrfs_root *btrfs_read_fs_root_no_name(struct btrfs_fs_info *fs_info,
 	root = btrfs_read_fs_root_no_radix(fs_info->tree_root, location);
 	if (IS_ERR(root))
 		return root;
+
+	set_anon_super(&root->anon_super, NULL);
+
 	ret = radix_tree_insert(&fs_info->fs_roots_radix,
 				(unsigned long)root->root_key.objectid,
 				root);
@@ -1950,6 +1959,10 @@ int btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
 {
 	radix_tree_delete(&fs_info->fs_roots_radix,
 			  (unsigned long)root->root_key.objectid);
+	if (root->anon_super.s_dev) {
+		down_write(&root->anon_super.s_umount);
+		kill_anon_super(&root->anon_super);
+	}
 	if (root->in_sysfs)
 		btrfs_sysfs_del_root(root);
 	if (root->node)