Btrfs: Allow subvolumes and snapshots anywhere in the directory tree

Before, all snapshots and subvolumes lived in a single flat directory.  This
was awkward and confusing because the single flat directory was only writable
with the ioctls.

This commit changes the ioctls to create subvols and snapshots at any
point in the directory tree.  This requires making separate ioctls for
snapshot and subvol creation instead of a combining them into one.

The subvol ioctl does:

btrfsctl -S subvol_name parent_dir

After the ioctl is done subvol_name lives inside parent_dir.

The snapshot ioctl does:

btrfsctl -s path_for_snapshot root_to_snapshot

path_for_snapshot can be an absolute or relative path.  btrfsctl breaks it up
into directory and basename components.

root_to_snapshot can be any file or directory in the FS.  The snapshot
is taken of the entire root where that file lives.

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

1 files changed, 5 insertions, 5 deletions

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 92393cc60d08..77c5eff3e209 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -285,11 +285,11 @@ static int btrfs_parse_early_options(const char *options, int flags,
  out:
         /*
          * If no subvolume name is specified we use the default one.  Allocate
-         * a copy of the string "default" here so that code later in the
+         * a copy of the string "." here so that code later in the
          * mount path doesn't care if it's the default volume or another one.
          */
         if (!*subvol_name) {
-                *subvol_name = kstrdup("default", GFP_KERNEL);
+                *subvol_name = kstrdup(".", GFP_KERNEL);
                 if (!*subvol_name)
                         return -ENOMEM;
         }
@@ -323,12 +323,12 @@ static int btrfs_fill_super(struct super_block * sb,
         }
         sb->s_fs_info = tree_root;
         disk_super = &tree_root->fs_info->super_copy;
-        inode = btrfs_iget_locked(sb, btrfs_super_root_dir(disk_super),
-                                  tree_root);
+        inode = btrfs_iget_locked(sb, BTRFS_FIRST_FREE_OBJECTID,
+                                  tree_root->fs_info->fs_root);
         bi = BTRFS_I(inode);
         bi->location.objectid = inode->i_ino;
         bi->location.offset = 0;
-        bi->root = tree_root;
+        bi->root = tree_root->fs_info->fs_root;
 
         btrfs_set_key_type(&bi->location, BTRFS_INODE_ITEM_KEY);