linux/fs/btrfs/uuid-tree.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) STRATO AG 2013.  All rights reserved.
 */

#include <linux/kthread.h>
#include <linux/uuid.h>
#include <asm/unaligned.h>
#include "messages.h"
#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "fs.h"
#include "accessors.h"
#include "uuid-tree.h"
#include "ioctl.h"

static void btrfs_uuid_to_key(const 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, const 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(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, const u8 *uuid, u8 type,
			u64 subid_cpu)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	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(trans, path, sizeof(subid_le));
		eb = path->nodes[0];
		slot = path->slots[0];
		offset = btrfs_item_ptr_offset(eb, slot);
		offset += btrfs_item_size(eb, slot) - sizeof(subid_le);
	} else {
		btrfs_warn(fs_info,
			   "insert uuid item failed %d (0x%016llx, 0x%016llx) type %u!",
			   ret, key.objectid, 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(trans, eb);

out:
	btrfs_free_path(path);
	return ret;
}

int btrfs_uuid_tree_remove(struct btrfs_trans_handle *trans, const u8 *uuid, u8 type,
			u64 subid)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	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(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(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(trans, 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_remove(trans, uuid, type, subid);
	btrfs_end_transaction(trans);

out:
	return ret;
}

/*
 * Check if there's an matching subvolume for given UUID
 *
 * Return:
 * 0	check succeeded, the entry is not outdated
 * > 0	if the check failed, the caller should remove the entry
 * < 0	if an error occurred
 */
static int btrfs_check_uuid_tree_entry(struct btrfs_fs_info *fs_info,
				       const u8 *uuid, u8 type, u64 subvolid)
{
	int ret = 0;
	struct btrfs_root *subvol_root;

	if (type != BTRFS_UUID_KEY_SUBVOL &&
	    type != BTRFS_UUID_KEY_RECEIVED_SUBVOL)
		goto out;

	subvol_root = btrfs_get_fs_root(fs_info, subvolid, true);
	if (IS_ERR(subvol_root)) {
		ret = PTR_ERR(subvol_root);
		if (ret == -ENOENT)
			ret = 1;
		goto out;
	}

	switch (type) {
	case BTRFS_UUID_KEY_SUBVOL:
		if (memcmp(uuid, subvol_root->root_item.uuid, BTRFS_UUID_SIZE))
			ret = 1;
		break;
	case BTRFS_UUID_KEY_RECEIVED_SUBVOL:
		if (memcmp(uuid, subvol_root->root_item.received_uuid,
			   BTRFS_UUID_SIZE))
			ret = 1;
		break;
	}
	btrfs_put_root(subvol_root);
out:
	return ret;
}

int btrfs_uuid_tree_iterate(struct btrfs_fs_info *fs_info)
{
	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, BTRFS_OLDEST_GENERATION);
	if (ret) {
		if (ret > 0)
			ret = 0;
		goto out;
	}

	while (1) {
		if (btrfs_fs_closing(fs_info)) {
			ret = -EINTR;
			goto out;
		}
		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(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 = btrfs_check_uuid_tree_entry(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;
				key.offset++;
				goto again_search_slot;
			}
			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;
}

int btrfs_uuid_scan_kthread(void *data)
{
	struct btrfs_fs_info *fs_info = data;
	struct btrfs_root *root = fs_info->tree_root;
	struct btrfs_key key;
	struct btrfs_path *path = NULL;
	int ret = 0;
	struct extent_buffer *eb;
	int slot;
	struct btrfs_root_item root_item;
	u32 item_size;
	struct btrfs_trans_handle *trans = NULL;
	bool closing = false;

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

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

	while (1) {
		if (btrfs_fs_closing(fs_info)) {
			closing = true;
			break;
		}
		ret = btrfs_search_forward(root, &key, path,
				BTRFS_OLDEST_GENERATION);
		if (ret) {
			if (ret > 0)
				ret = 0;
			break;
		}

		if (key.type != BTRFS_ROOT_ITEM_KEY ||
		    (key.objectid < BTRFS_FIRST_FREE_OBJECTID &&
		     key.objectid != BTRFS_FS_TREE_OBJECTID) ||
		    key.objectid > BTRFS_LAST_FREE_OBJECTID)
			goto skip;

		eb = path->nodes[0];
		slot = path->slots[0];
		item_size = btrfs_item_size(eb, slot);
		if (item_size < sizeof(root_item))
			goto skip;

		read_extent_buffer(eb, &root_item,
				   btrfs_item_ptr_offset(eb, slot),
				   (int)sizeof(root_item));
		if (btrfs_root_refs(&root_item) == 0)
			goto skip;

		if (!btrfs_is_empty_uuid(root_item.uuid) ||
		    !btrfs_is_empty_uuid(root_item.received_uuid)) {
			if (trans)
				goto update_tree;

			btrfs_release_path(path);
			/*
			 * 1 - subvol uuid item
			 * 1 - received_subvol uuid item
			 */
			trans = btrfs_start_transaction(fs_info->uuid_root, 2);
			if (IS_ERR(trans)) {
				ret = PTR_ERR(trans);
				break;
			}
			continue;
		} else {
			goto skip;
		}
update_tree:
		btrfs_release_path(path);
		if (!btrfs_is_empty_uuid(root_item.uuid)) {
			ret = btrfs_uuid_tree_add(trans, root_item.uuid,
						  BTRFS_UUID_KEY_SUBVOL,
						  key.objectid);
			if (ret < 0) {
				btrfs_warn(fs_info, "uuid_tree_add failed %d",
					ret);
				break;
			}
		}

		if (!btrfs_is_empty_uuid(root_item.received_uuid)) {
			ret = btrfs_uuid_tree_add(trans,
						  root_item.received_uuid,
						 BTRFS_UUID_KEY_RECEIVED_SUBVOL,
						  key.objectid);
			if (ret < 0) {
				btrfs_warn(fs_info, "uuid_tree_add failed %d",
					ret);
				break;
			}
		}

skip:
		btrfs_release_path(path);
		if (trans) {
			ret = btrfs_end_transaction(trans);
			trans = NULL;
			if (ret)
				break;
		}

		if (key.offset < (u64)-1) {
			key.offset++;
		} else if (key.type < BTRFS_ROOT_ITEM_KEY) {
			key.offset = 0;
			key.type = BTRFS_ROOT_ITEM_KEY;
		} else if (key.objectid < (u64)-1) {
			key.offset = 0;
			key.type = BTRFS_ROOT_ITEM_KEY;
			key.objectid++;
		} else {
			break;
		}
		cond_resched();
	}

out:
	btrfs_free_path(path);
	if (trans && !IS_ERR(trans))
		btrfs_end_transaction(trans);
	if (ret)
		btrfs_warn(fs_info, "btrfs_uuid_scan_kthread failed %d", ret);
	else if (!closing)
		set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);
	up(&fs_info->uuid_tree_rescan_sem);
	return 0;
}

int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
{
	struct btrfs_trans_handle *trans;
	struct btrfs_root *tree_root = fs_info->tree_root;
	struct btrfs_root *uuid_root;
	struct task_struct *task;
	int ret;

	/*
	 * 1 - root node
	 * 1 - root item
	 */
	trans = btrfs_start_transaction(tree_root, 2);
	if (IS_ERR(trans))
		return PTR_ERR(trans);

	uuid_root = btrfs_create_tree(trans, BTRFS_UUID_TREE_OBJECTID);
	if (IS_ERR(uuid_root)) {
		ret = PTR_ERR(uuid_root);
		btrfs_abort_transaction(trans, ret);
		btrfs_end_transaction(trans);
		return ret;
	}

	fs_info->uuid_root = uuid_root;

	ret = btrfs_commit_transaction(trans);
	if (ret)
		return ret;

	down(&fs_info->uuid_tree_rescan_sem);
	task = kthread_run(btrfs_uuid_scan_kthread, fs_info, "btrfs-uuid");
	if (IS_ERR(task)) {
		/* fs_info->update_uuid_tree_gen remains 0 in all error case */
		btrfs_warn(fs_info, "failed to start uuid_scan task");
		up(&fs_info->uuid_tree_rescan_sem);
		return PTR_ERR(task);
	}

	return 0;
}