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

#include <linux/kthread.h>
#include <linux/uuid.h>
#include <linux/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;
        BTRFS_PATH_AUTO_FREE(path);
        struct extent_buffer *eb;
        int slot;
        u32 item_size;
        unsigned long offset;
        struct btrfs_key key;

        if (WARN_ON_ONCE(!uuid_root))
                return -ENOENT;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        btrfs_uuid_to_key(uuid, type, &key);
        ret = btrfs_search_slot(NULL, uuid_root, &key, path, 0, 0);
        if (ret < 0)
                return ret;
        if (ret > 0)
                return -ENOENT;

        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);
                return ret;
        }
        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);
        }

        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;
        BTRFS_PATH_AUTO_FREE(path);
        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))
                return -EINVAL;

        btrfs_uuid_to_key(uuid, type, &key);

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        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);
                return ret;
        }

        subid_le = cpu_to_le64(subid_cpu);
        write_extent_buffer(eb, &subid_le, offset, sizeof(subid_le));
        return 0;
}

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;
        BTRFS_PATH_AUTO_FREE(path);
        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))
                return -EINVAL;

        btrfs_uuid_to_key(uuid, type, &key);

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        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);
                return ret;
        }
        if (ret > 0)
                return -ENOENT;

        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);
                return -ENOENT;
        }
        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)
                return -ENOENT;

        item_size = btrfs_item_size(eb, slot);
        if (item_size == sizeof(subid))
                return btrfs_del_item(trans, uuid_root, path);

        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);

        return 0;
}

/*
 * Check if we can add one root ID to a UUID key.
 * If the key does not yet exists, we can, otherwise only if extended item does
 * not exceeds the maximum item size permitted by the leaf size.
 *
 * Returns 0 on success, negative value on error.
 */
int btrfs_uuid_tree_check_overflow(struct btrfs_fs_info *fs_info,
                                   const u8 *uuid, u8 type)
{
        BTRFS_PATH_AUTO_FREE(path);
        int ret;
        u32 item_size;
        struct btrfs_key key;

        if (WARN_ON_ONCE(!fs_info->uuid_root))
                return -EINVAL;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        btrfs_uuid_to_key(uuid, type, &key);
        ret = btrfs_search_slot(NULL, fs_info->uuid_root, &key, path, 0, 0);
        if (ret < 0)
                return ret;
        if (ret > 0)
                return 0;

        item_size = btrfs_item_size(path->nodes[0], path->slots[0]);

        if (sizeof(struct btrfs_item) + item_size + sizeof(u64) >
            BTRFS_LEAF_DATA_SIZE(fs_info))
                return -EOVERFLOW;

        return 0;
}

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))
                return PTR_ERR(trans);

        ret = btrfs_uuid_tree_remove(trans, uuid, type, subid);
        btrfs_end_transaction(trans);
        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)
                return 0;

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

        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);

        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;
        BTRFS_PATH_AUTO_FREE(path);
        int ret = 0;
        struct extent_buffer *leaf;
        int slot;
        u32 item_size;
        unsigned long offset;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

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

again_search_slot:
        ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION);
        if (ret < 0)
                return ret;
        if (ret > 0)
                return 0;

        while (1) {
                if (btrfs_fs_closing(fs_info))
                        return -EINTR;

                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)
                                return ret;
                        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)
                                        return ret;
                                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;
        }

        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;
}