On Mon, 2010-10-11 at 20:08 +0200, Goffredo Baroncelli wrote: > Hi all, > > enclosed you can find a patch which permits to remove a volume via the > rmdir(2) syscall by an ordinary user. > The rules for a subvolume removal are the same ones of a directory: > - the user must have the write permission on the parent directory > - the subvolume must be empty > > The mains differences between calling rmdir(2) on a subvolume and calling the > BTRFS_IOC_SNAP_DESTROY ioctl are: > > - rmdir(2) requires the subvolume to be empty (the user has to empty the > subvolume before removing it, like the rm -rf command does) > - rmdir(2) is a synchronous operation (instead BTRFS_IOC_SNAP_DESTROY works > in background) > > The previous statements have the following (nice) consequences: > - the CAP_ADMIN capability is not required anymore to remove a subvolume. > BTRFS_IOC_SNAP_DESTROY requires CAP_ADMIN because the subvolume removal is > performed in background so it would not be possible to return an error if > the user has not the privilege of removing a file. > - when the rmdir(2) syscall returns the space is really freed, and there is > no necessity to create another API to wait the ends of the > BTRFS_IOC_SNAP_DESTROY ioctl. > > The only advantage of the BTRFS_IOC_SNAP_DESTROY ioctl is its greater speed > in removing a not empty subvolume. > > I simplify the code respect my previous post, removing a un-needed call to the > function may_destroy_subvol(). > > You can pull the code from the branch named "rmdir-subvolume" of the following > repository: > > http://cassiopea.homelinux.net/git/btrfs-unstable.git > > As usual, comments are welcome > > Regards > G.Baroncelli > > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index f08427c..0df2fb0 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -2944,6 +2944,84 @@ int btrfs_unlink_subvol(struct btrfs_trans_handle *trans, > return 0; > } > > +static noinline int btrfs_snap_destroy(struct inode *dir, > + struct dentry *dentry) > +{ > + > + struct inode *inode; > + struct btrfs_root *root = BTRFS_I(dir)->root; > + struct btrfs_root *dest = NULL; > + struct btrfs_trans_handle *trans; > + int ret; > + int err = 0; > + > + if (IS_ERR(dentry)) { > + err = PTR_ERR(dentry); > + goto out; > + } > + > + if (!dentry->d_inode) { > + err = -ENOENT; > + goto out; > + } > + > + inode = dentry->d_inode; > + if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID) { > + err = -EINVAL; > + goto out; > + } > + > + dest = BTRFS_I(inode)->root; > + > + down_write(&root->fs_info->subvol_sem); > + > + /* remove this check because the directory is empty. > + * err = may_destroy_subvol(dest); > + * if (err) > + * goto out_up_write; > + */ > + > + trans = btrfs_start_transaction(root, 0); > + if (IS_ERR(trans)) { > + err = PTR_ERR(trans); > + goto out_up_write; > + } > + trans->block_rsv = &root->fs_info->global_block_rsv; > + > + ret = btrfs_unlink_subvol(trans, root, dir, > + dest->root_key.objectid, > + dentry->d_name.name, > + dentry->d_name.len); > + BUG_ON(ret); Is it really a good idea to add even more dead end BUG_ON() calls instead of handling errors when they happen? > + > + btrfs_record_root_in_trans(trans, dest); > + > + memset(&dest->root_item.drop_progress, 0, > + sizeof(dest->root_item.drop_progress)); > + dest->root_item.drop_level = 0; > + btrfs_set_root_refs(&dest->root_item, 0); > + > + if (!xchg(&dest->orphan_item_inserted, 1)) { > + ret = btrfs_insert_orphan_item(trans, > + root->fs_info->tree_root, > + dest->root_key.objectid); > + BUG_ON(ret); > + } > + > + ret = btrfs_commit_transaction(trans, root); > + BUG_ON(ret); > + inode->i_flags |= S_DEAD; > +out_up_write: > + up_write(&root->fs_info->subvol_sem); > + if (!err) { > + shrink_dcache_sb(root->fs_info->sb); > + btrfs_invalidate_inodes(dest); > + /*d_delete(dentry);*/ > + } > +out: > + return err; > +} > + > static int btrfs_rmdir(struct inode *dir, struct dentry *dentry) > { > struct inode *inode = dentry->d_inode; > @@ -2952,10 +3030,12 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry) > struct btrfs_trans_handle *trans; > unsigned long nr = 0; > > - if (inode->i_size > BTRFS_EMPTY_DIR_SIZE || > - inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) > + if (inode->i_size > BTRFS_EMPTY_DIR_SIZE) > return -ENOTEMPTY; > > + if (inode->i_ino == BTRFS_FIRST_FREE_OBJECTID) > + return btrfs_snap_destroy(dir, dentry); > + > trans = __unlink_start_trans(dir, dentry); > if (IS_ERR(trans)) > return PTR_ERR(trans); > > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
