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, 52 insertions, 19 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f43df72b0e17..ec45b3086136 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -67,6 +67,7 @@ static noinline int create_subvol(struct btrfs_root *root,
 	int err;
 	u64 objectid;
 	u64 new_dirid = BTRFS_FIRST_FREE_OBJECTID;
+	u64 index = 0;
 	unsigned long nr = 1;
 
 	ret = btrfs_check_free_space(root, 1, 0);
@@ -126,6 +127,7 @@ static noinline int create_subvol(struct btrfs_root *root,
 	key.objectid = objectid;
 	key.offset = 1;
 	btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
+printk("inserting root objectid %Lu\n", objectid);
 	ret = btrfs_insert_root(trans, root->fs_info->tree_root, &key,
 				&root_item);
 	if (ret)
@@ -135,24 +137,27 @@ static noinline int create_subvol(struct btrfs_root *root,
 	 * insert the directory item
 	 */
 	key.offset = (u64)-1;
-	dir = root->fs_info->sb->s_root->d_inode;
-	ret = btrfs_insert_dir_item(trans, root->fs_info->tree_root,
+	dir = dentry->d_parent->d_inode;
+	ret = btrfs_set_inode_index(dir, &index);
+	BUG_ON(ret);
+
+	ret = btrfs_insert_dir_item(trans, root,
 				    name, namelen, dir->i_ino, &key,
-				    BTRFS_FT_DIR, 0);
+				    BTRFS_FT_DIR, index);
 	if (ret)
 		goto fail;
-
+#if 0
 	ret = btrfs_insert_inode_ref(trans, root->fs_info->tree_root,
 			     name, namelen, objectid,
 			     root->fs_info->sb->s_root->d_inode->i_ino, 0);
 	if (ret)
 		goto fail;
-
+#endif
 	ret = btrfs_commit_transaction(trans, root);
 	if (ret)
 		goto fail_commit;
 
-	new_root = btrfs_read_fs_root(root->fs_info, &key, name, namelen);
+	new_root = btrfs_read_fs_root_no_name(root->fs_info, &key);
 	BUG_ON(!new_root);
 
 	trans = btrfs_start_transaction(new_root, 1);
@@ -170,14 +175,16 @@ fail:
 		ret = err;
 fail_commit:
 	btrfs_btree_balance_dirty(root, nr);
+printk("all done ret %d\n", ret);
 	return ret;
 }
 
-static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
+static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
+			   char *name, int namelen)
 {
 	struct btrfs_pending_snapshot *pending_snapshot;
 	struct btrfs_trans_handle *trans;
-	int ret;
+	int ret = 0;
 	int err;
 	unsigned long nr = 0;
 
@@ -188,7 +195,7 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
 	if (ret)
 		goto fail_unlock;
 
-	pending_snapshot = kmalloc(sizeof(*pending_snapshot), GFP_NOFS);
+	pending_snapshot = kzalloc(sizeof(*pending_snapshot), GFP_NOFS);
 	if (!pending_snapshot) {
 		ret = -ENOMEM;
 		goto fail_unlock;
@@ -201,12 +208,12 @@ static int create_snapshot(struct btrfs_root *root, char *name, int namelen)
 	}
 	memcpy(pending_snapshot->name, name, namelen);
 	pending_snapshot->name[namelen] = '\0';
+	pending_snapshot->dentry = dentry;
 	trans = btrfs_start_transaction(root, 1);
 	BUG_ON(!trans);
 	pending_snapshot->root = root;
 	list_add(&pending_snapshot->list,
 		 &trans->transaction->pending_snapshots);
-	ret = btrfs_update_inode(trans, root, root->inode);
 	err = btrfs_commit_transaction(trans, root);
 
 fail_unlock:
@@ -230,7 +237,8 @@ static inline int btrfs_may_create(struct inode *dir, struct dentry *child)
  * inside this filesystem so it's quite a bit simpler.
  */
 static noinline int btrfs_mksubvol(struct path *parent, char *name,
-				   int mode, int namelen)
+				   int mode, int namelen,
+				   struct btrfs_root *snap_src)
 {
 	struct dentry *dentry;
 	int error;
@@ -248,6 +256,7 @@ static noinline int btrfs_mksubvol(struct path *parent, char *name,
 
 	if (!IS_POSIXACL(parent->dentry->d_inode))
 		mode &= ~current->fs->umask;
+
 	error = mnt_want_write(parent->mnt);
 	if (error)
 		goto out_dput;
@@ -266,8 +275,12 @@ static noinline int btrfs_mksubvol(struct path *parent, char *name,
 	 * Also we should pass on the mode eventually to allow creating new
 	 * subvolume with specific mode bits.
 	 */
-	error = create_subvol(BTRFS_I(parent->dentry->d_inode)->root, dentry,
-			      name, namelen);
+	if (snap_src) {
+		error = create_snapshot(snap_src, dentry, name, namelen);
+	} else {
+		error = create_subvol(BTRFS_I(parent->dentry->d_inode)->root,
+				      dentry, name, namelen);
+	}
 	if (error)
 		goto out_drop_write;
 
@@ -471,15 +484,16 @@ out:
 }
 
 static noinline int btrfs_ioctl_snap_create(struct file *file,
-					    void __user *arg)
+					    void __user *arg, int subvol)
 {
 	struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
 	struct btrfs_ioctl_vol_args *vol_args;
 	struct btrfs_dir_item *di;
 	struct btrfs_path *path;
+	struct file *src_file;
 	u64 root_dirid;
 	int namelen;
-	int ret;
+	int ret = 0;
 
 	if (root->fs_info->sb->s_flags & MS_RDONLY)
 		return -EROFS;
@@ -523,12 +537,29 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
 		goto out;
 	}
 
-	if (root == root->fs_info->tree_root) {
+	if (subvol) {
 		ret = btrfs_mksubvol(&file->f_path, vol_args->name,
 				     file->f_path.dentry->d_inode->i_mode,
-				     namelen);
+				     namelen, NULL);
 	} else {
-		ret = create_snapshot(root, vol_args->name, namelen);
+		struct inode *src_inode;
+		src_file = fget(vol_args->fd);
+		if (!src_file) {
+			ret = -EINVAL;
+			goto out;
+		}
+
+		src_inode = src_file->f_path.dentry->d_inode;
+		if (src_inode->i_sb != file->f_path.dentry->d_inode->i_sb) {
+			printk("btrfs: Snapshot src from another FS\n");
+			ret = -EINVAL;
+			fput(src_file);
+			goto out;
+		}
+		ret = btrfs_mksubvol(&file->f_path, vol_args->name,
+			     file->f_path.dentry->d_inode->i_mode,
+			     namelen, BTRFS_I(src_inode)->root);
+		fput(src_file);
 	}
 
 out:
@@ -1030,7 +1061,9 @@ long btrfs_ioctl(struct file *file, unsigned int
 
 	switch (cmd) {
 	case BTRFS_IOC_SNAP_CREATE:
-		return btrfs_ioctl_snap_create(file, (void __user *)arg);
+		return btrfs_ioctl_snap_create(file, (void __user *)arg, 0);
+	case BTRFS_IOC_SUBVOL_CREATE:
+		return btrfs_ioctl_snap_create(file, (void __user *)arg, 1);
 	case BTRFS_IOC_DEFRAG:
 		return btrfs_ioctl_defrag(file);
 	case BTRFS_IOC_RESIZE: