alistair23-linux/fs/btrfs/uuid-tree.c

/*
 * Copyright (C) STRATO AG 2013.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */
#include <linux/uuid.h>
#include <asm/unaligned.h>
#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "print-tree.h"


static void btrfs_uuid_to_key(u8 *uuid, u8 type, struct btrfs_key *key)
{
	key->type = type;
	key->objectid = get_unaligned_le64(uuid);
	key->offset = get_unaligned_le64(uuid + sizeof(u64));
}

/* return -ENOENT for !found, < 0 for errors, or 0 if an item was found */
static int btrfs_uuid_tree_lookup(struct btrfs_root *uuid_root, u8 *uuid,
				  u8 type, u64 subid)
{
	int ret;
	struct btrfs_path *path = NULL;
	struct extent_buffer *eb;
	int slot;
	u32 item_size;
	unsigned long offset;
	struct btrfs_key key;

	if (WARN_ON_ONCE(!uuid_root)) {
		ret = -ENOENT;
		goto out;
	}

	path = btrfs_alloc_path();
	if (!path) {
		ret = -ENOMEM;
		goto out;
	}

	btrfs_uuid_to_key(uuid, type, &key);
	ret = btrfs_search_slot(NULL, uuid_root, &key, path, 0, 0);
	if (ret < 0) {
		goto out;
	} else if (ret > 0) {
		ret = -ENOENT;
		goto out;
	}

	eb = path->nodes[0];
	slot = path->slots[0];
	item_size = btrfs_item_size_nr(eb, slot);
	offset = btrfs_item_ptr_offset(eb, slot);
	ret = -ENOENT;

	if (!IS_ALIGNED(item_size, sizeof(u64))) {
		btrfs_warn(uuid_root->fs_info,
			   "uuid item with illegal size %lu!",
			   (unsigned long)item_size);
		goto out;
	}
	while (item_size) {
		__le64 data;

		read_extent_buffer(eb, &data, offset, sizeof(data));
		if (le64_to_cpu(data) == subid) {
			ret = 0;
			break;
		}
		offset += sizeof(data);
		item_size -= sizeof(data);
	}

out:
	btrfs_free_path(path);
	return ret;
}

int btrfs_uuid_tree_add(struct btrfs_trans_handle *trans,
			struct btrfs_fs_info *fs_info, u8 *uuid, u8 type,
			u64 subid_cpu)
{
	struct btrfs_root *uuid_root = fs_info->uuid_root;
	int ret;
	struct btrfs_path *path = NULL;
	struct btrfs_key key;
	struct extent_buffer *eb;
	int slot;
	unsigned long offset;
	__le64 subid_le;

	ret = btrfs_uuid_tree_lookup(uuid_root, uuid, type, subid_cpu);
	if (ret != -ENOENT)
		return ret;

	if (WARN_ON_ONCE(!uuid_root)) {
		ret = -EINVAL;
		goto out;
	}

	btrfs_uuid_to_key(uuid, type, &key);

	path = btrfs_alloc_path();
	if (!path) {
		ret = -ENOMEM;
		goto out;
	}

	ret = btrfs_insert_empty_item(trans, uuid_root, path, &key,
				      sizeof(subid_le));
	if (ret >= 0) {
		/* Add an item for the type for the first time */
		eb = path->nodes[0];
		slot = path->slots[0];
		offset = btrfs_item_ptr_offset(eb, slot);
	} else if (ret == -EEXIST) {
		/*
		 * An item with that type already exists.
		 * Extend the item and store the new subid at the end.
		 */
		btrfs_extend_item(fs_info, path, sizeof(subid_le));
		eb = path->nodes[0];
		slot = path->slots[0];
		offset = btrfs_item_ptr_offset(eb, slot);
		offset += btrfs_item_size_nr(eb, slot) - sizeof(subid_le);
	} else if (ret < 0) {
		btrfs_warn(fs_info,
			   "insert uuid item failed %d (0x%016llx, 0x%016llx) type %u!",
			   ret, (unsigned long long)key.objectid,
			   (unsigned long long)key.offset, type);
		goto out;
	}

	ret = 0;
	subid_le = cpu_to_le64(subid_cpu);
	write_extent_buffer(eb, &subid_le, offset, sizeof(subid_le));
	btrfs_mark_buffer_dirty(eb);

out:
	btrfs_free_path(path);
	return ret;
}

int btrfs_uuid_tree_rem(struct btrfs_trans_handle *trans,
			struct btrfs_fs_info *fs_info, u8 *uuid, u8 type,
			u64 subid)
{
	struct btrfs_root *uuid_root = fs_info->uuid_root;
	int ret;
	struct btrfs_path *path = NULL;
	struct btrfs_key key;
	struct extent_buffer *eb;
	int slot;
	unsigned long offset;
	u32 item_size;
	unsigned long move_dst;
	unsigned long move_src;
	unsigned long move_len;

	if (WARN_ON_ONCE(!uuid_root)) {
		ret = -EINVAL;
		goto out;
	}

	btrfs_uuid_to_key(uuid, type, &key);

	path = btrfs_alloc_path();
	if (!path) {
		ret = -ENOMEM;
		goto out;
	}

	ret = btrfs_search_slot(trans, uuid_root, &key, path, -1, 1);
	if (ret < 0) {
		btrfs_warn(fs_info, "error %d while searching for uuid item!",
			   ret);
		goto out;
	}
	if (ret > 0) {
		ret = -ENOENT;
		goto out;
	}

	eb = path->nodes[0];
	slot = path->slots[0];
	offset = btrfs_item_ptr_offset(eb, slot);
	item_size = btrfs_item_size_nr(eb, slot);
	if (!IS_ALIGNED(item_size, sizeof(u64))) {
		btrfs_warn(fs_info, "uuid item with illegal size %lu!",
			   (unsigned long)item_size);
		ret = -ENOENT;
		goto out;
	}
	while (item_size) {
		__le64 read_subid;

		read_extent_buffer(eb, &read_subid, offset, sizeof(read_subid));
		if (le64_to_cpu(read_subid) == subid)
			break;
		offset += sizeof(read_subid);
		item_size -= sizeof(read_subid);
	}

	if (!item_size) {
		ret = -ENOENT;
		goto out;
	}

	item_size = btrfs_item_size_nr(eb, slot);
	if (item_size == sizeof(subid)) {
		ret = btrfs_del_item(trans, uuid_root, path);
		goto out;
	}

	move_dst = offset;
	move_src = offset + sizeof(subid);
	move_len = item_size - (move_src - btrfs_item_ptr_offset(eb, slot));
	memmove_extent_buffer(eb, move_dst, move_src, move_len);
	btrfs_truncate_item(fs_info, path, item_size - sizeof(subid), 1);

out:
	btrfs_free_path(path);
	return ret;
}

static int btrfs_uuid_iter_rem(struct btrfs_root *uuid_root, u8 *uuid, u8 type,
			       u64 subid)
{
	struct btrfs_trans_handle *trans;
	int ret;

	/* 1 - for the uuid item */
	trans = btrfs_start_transaction(uuid_root, 1);
	if (IS_ERR(trans)) {
		ret = PTR_ERR(trans);
		goto out;
	}

	ret = btrfs_uuid_tree_rem(trans, uuid_root->fs_info, uuid, type, subid);
	btrfs_end_transaction(trans);

out:
	return ret;
}

int btrfs_uuid_tree_iterate(struct btrfs_fs_info *fs_info,
			    int (*check_func)(struct btrfs_fs_info *, u8 *, u8,
					      u64))
{
	struct btrfs_root *root = fs_info->uuid_root;
	struct btrfs_key key;
	struct btrfs_path *path;
	int ret = 0;
	struct extent_buffer *leaf;
	int slot;
	u32 item_size;
	unsigned long offset;

	path = btrfs_alloc_path();
	if (!path) {
		ret = -ENOMEM;
		goto out;
	}

	key.objectid = 0;
	key.type = 0;
	key.offset = 0;

again_search_slot:
	ret = btrfs_search_forward(root, &key, path, 0);
	if (ret) {
		if (ret > 0)
			ret = 0;
		goto out;
	}

	while (1) {
		cond_resched();
		leaf = path->nodes[0];
		slot = path->slots[0];
		btrfs_item_key_to_cpu(leaf, &key, slot);

		if (key.type != BTRFS_UUID_KEY_SUBVOL &&
		    key.type != BTRFS_UUID_KEY_RECEIVED_SUBVOL)
			goto skip;

		offset = btrfs_item_ptr_offset(leaf, slot);
		item_size = btrfs_item_size_nr(leaf, slot);
		if (!IS_ALIGNED(item_size, sizeof(u64))) {
			btrfs_warn(fs_info,
				   "uuid item with illegal size %lu!",
				   (unsigned long)item_size);
			goto skip;
		}
		while (item_size) {
			u8 uuid[BTRFS_UUID_SIZE];
			__le64 subid_le;
			u64 subid_cpu;

			put_unaligned_le64(key.objectid, uuid);
			put_unaligned_le64(key.offset, uuid + sizeof(u64));
			read_extent_buffer(leaf, &subid_le, offset,
					   sizeof(subid_le));
			subid_cpu = le64_to_cpu(subid_le);
			ret = check_func(fs_info, uuid, key.type, subid_cpu);
			if (ret < 0)
				goto out;
			if (ret > 0) {
				btrfs_release_path(path);
				ret = btrfs_uuid_iter_rem(root, uuid, key.type,
							  subid_cpu);
				if (ret == 0) {
					/*
					 * this might look inefficient, but the
					 * justification is that it is an
					 * exception that check_func returns 1,
					 * and that in the regular case only one
					 * entry per UUID exists.
					 */
					goto again_search_slot;
				}
				if (ret < 0 && ret != -ENOENT)
					goto out;
			}
			item_size -= sizeof(subid_le);
			offset += sizeof(subid_le);
		}

skip:
		ret = btrfs_next_item(root, path);
		if (ret == 0)
			continue;
		else if (ret > 0)
			ret = 0;
		break;
	}

out:
	btrfs_free_path(path);
	return ret;
}