/*
 * Copyright (C) 2007 Oracle.  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/err.h>
#include <linux/uuid.h>
#include "ctree.h"
#include "transaction.h"
#include "disk-io.h"
#include "print-tree.h"

/*
 * Read a root item from the tree. In case we detect a root item smaller then
 * sizeof(root_item), we know it's an old version of the root structure and
 * initialize all new fields to zero. The same happens if we detect mismatching
 * generation numbers as then we know the root was once mounted with an older
 * kernel that was not aware of the root item structure change.
 */
static void btrfs_read_root_item(struct extent_buffer *eb, int slot,
                                struct btrfs_root_item *item)
{
        uuid_le uuid;
        int len;
        int need_reset = 0;

        len = btrfs_item_size_nr(eb, slot);
        read_extent_buffer(eb, item, btrfs_item_ptr_offset(eb, slot),
                        min_t(int, len, (int)sizeof(*item)));
        if (len < sizeof(*item))
                need_reset = 1;
        if (!need_reset && btrfs_root_generation(item)
                != btrfs_root_generation_v2(item)) {
                if (btrfs_root_generation_v2(item) != 0) {
                        printk(KERN_WARNING "BTRFS: mismatching "
                                        "generation and generation_v2 "
                                        "found in root item. This root "
                                        "was probably mounted with an "
                                        "older kernel. Resetting all "
                                        "new fields.\n");
                }
                need_reset = 1;
        }
        if (need_reset) {
                memset(&item->generation_v2, 0,
                        sizeof(*item) - offsetof(struct btrfs_root_item,
                                        generation_v2));

                uuid_le_gen(&uuid);
                memcpy(item->uuid, uuid.b, BTRFS_UUID_SIZE);
        }
}

/*
 * btrfs_find_root - lookup the root by the key.
 * root: the root of the root tree
 * search_key: the key to search
 * path: the path we search
 * root_item: the root item of the tree we look for
 * root_key: the reak key of the tree we look for
 *
 * If ->offset of 'seach_key' is -1ULL, it means we are not sure the offset
 * of the search key, just lookup the root with the highest offset for a
 * given objectid.
 *
 * If we find something return 0, otherwise > 0, < 0 on error.
 */
int btrfs_find_root(struct btrfs_root *root, struct btrfs_key *search_key,
                    struct btrfs_path *path, struct btrfs_root_item *root_item,
                    struct btrfs_key *root_key)
{
        struct btrfs_key found_key;
        struct extent_buffer *l;
        int ret;
        int slot;

        ret = btrfs_search_slot(NULL, root, search_key, path, 0, 0);
        if (ret < 0)
                return ret;

        if (search_key->offset != -1ULL) {      /* the search key is exact */
                if (ret > 0)
                        goto out;
        } else {
                BUG_ON(ret == 0);               /* Logical error */
                if (path->slots[0] == 0)
                        goto out;
                path->slots[0]--;
                ret = 0;
        }

        l = path->nodes[0];
        slot = path->slots[0];

        btrfs_item_key_to_cpu(l, &found_key, slot);
        if (found_key.objectid != search_key->objectid ||
            found_key.type != BTRFS_ROOT_ITEM_KEY) {
                ret = 1;
                goto out;
        }

        if (root_item)
                btrfs_read_root_item(l, slot, root_item);
        if (root_key)
                memcpy(root_key, &found_key, sizeof(found_key));
out:
        btrfs_release_path(path);
        return ret;
}

void btrfs_set_root_node(struct btrfs_root_item *item,
                         struct extent_buffer *node)
{
        btrfs_set_root_bytenr(item, node->start);
        btrfs_set_root_level(item, btrfs_header_level(node));
        btrfs_set_root_generation(item, btrfs_header_generation(node));
}

/*
 * copy the data in 'item' into the btree
 */
int btrfs_update_root(struct btrfs_trans_handle *trans, struct btrfs_root
                      *root, struct btrfs_key *key, struct btrfs_root_item
                      *item)
{
        struct btrfs_path *path;
        struct extent_buffer *l;
        int ret;
        int slot;
        unsigned long ptr;
        int old_len;

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

        ret = btrfs_search_slot(trans, root, key, path, 0, 1);
        if (ret < 0) {
                btrfs_abort_transaction(trans, root, ret);
                goto out;
        }

        if (ret != 0) {
                btrfs_print_leaf(root, path->nodes[0]);
                btrfs_crit(root->fs_info, "unable to update root key %llu %u %llu",
                       key->objectid, key->type, key->offset);
                BUG_ON(1);
        }

        l = path->nodes[0];
        slot = path->slots[0];
        ptr = btrfs_item_ptr_offset(l, slot);
        old_len = btrfs_item_size_nr(l, slot);

        /*
         * If this is the first time we update the root item which originated
         * from an older kernel, we need to enlarge the item size to make room
         * for the added fields.
         */
        if (old_len < sizeof(*item)) {
                btrfs_release_path(path);
                ret = btrfs_search_slot(trans, root, key, path,
                                -1, 1);
                if (ret < 0) {
                        btrfs_abort_transaction(trans, root, ret);
                        goto out;
                }

                ret = btrfs_del_item(trans, root, path);
                if (ret < 0) {
                        btrfs_abort_transaction(trans, root, ret);
                        goto out;
                }
                btrfs_release_path(path);
                ret = btrfs_insert_empty_item(trans, root, path,
                                key, sizeof(*item));
                if (ret < 0) {
                        btrfs_abort_transaction(trans, root, ret);
                        goto out;
                }
                l = path->nodes[0];
                slot = path->slots[0];
                ptr = btrfs_item_ptr_offset(l, slot);
        }

        /*
         * Update generation_v2 so at the next mount we know the new root
         * fields are valid.
         */
        btrfs_set_root_generation_v2(item, btrfs_root_generation(item));

        write_extent_buffer(l, item, ptr, sizeof(*item));
        btrfs_mark_buffer_dirty(path->nodes[0]);
out:
        btrfs_free_path(path);
        return ret;
}

int btrfs_insert_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                      struct btrfs_key *key, struct btrfs_root_item *item)
{
        /*
         * Make sure generation v1 and v2 match. See update_root for details.
         */
        btrfs_set_root_generation_v2(item, btrfs_root_generation(item));
        return btrfs_insert_item(trans, root, key, item, sizeof(*item));
}

int btrfs_find_orphan_roots(struct btrfs_root *tree_root)
{
        struct extent_buffer *leaf;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct btrfs_key root_key;
        struct btrfs_root *root;
        int err = 0;
        int ret;
        bool can_recover = true;

        if (tree_root->fs_info->sb->s_flags & MS_RDONLY)
                can_recover = false;

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

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

        root_key.type = BTRFS_ROOT_ITEM_KEY;
        root_key.offset = (u64)-1;

        while (1) {
                ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
                if (ret < 0) {
                        err = ret;
                        break;
                }

                leaf = path->nodes[0];
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(tree_root, path);
                        if (ret < 0)
                                err = ret;
                        if (ret != 0)
                                break;
                        leaf = path->nodes[0];
                }

                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                btrfs_release_path(path);

                if (key.objectid != BTRFS_ORPHAN_OBJECTID ||
                    key.type != BTRFS_ORPHAN_ITEM_KEY)
                        break;

                root_key.objectid = key.offset;
                key.offset++;

                root = btrfs_read_fs_root(tree_root, &root_key);
                err = PTR_ERR_OR_ZERO(root);
                if (err && err != -ENOENT) {
                        break;
                } else if (err == -ENOENT) {
                        struct btrfs_trans_handle *trans;

                        btrfs_release_path(path);

                        trans = btrfs_join_transaction(tree_root);
                        if (IS_ERR(trans)) {
                                err = PTR_ERR(trans);
                                btrfs_error(tree_root->fs_info, err,
                                            "Failed to start trans to delete "
                                            "orphan item");
                                break;
                        }
                        err = btrfs_del_orphan_item(trans, tree_root,
                                                    root_key.objectid);
                        btrfs_end_transaction(trans, tree_root);
                        if (err) {
                                btrfs_error(tree_root->fs_info, err,
                                            "Failed to delete root orphan "
                                            "item");
                                break;
                        }
                        continue;
                }

                err = btrfs_init_fs_root(root);
                if (err) {
                        btrfs_free_fs_root(root);
                        break;
                }

                set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);

                err = btrfs_insert_fs_root(root->fs_info, root);
                if (err) {
                        BUG_ON(err == -EEXIST);
                        btrfs_free_fs_root(root);
                        break;
                }

                if (btrfs_root_refs(&root->root_item) == 0)
                        btrfs_add_dead_root(root);
        }

        btrfs_free_path(path);
        return err;
}

/* drop the root item for 'key' from 'root' */
int btrfs_del_root(struct btrfs_trans_handle *trans, struct btrfs_root *root,
                   struct btrfs_key *key)
{
        struct btrfs_path *path;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
        ret = btrfs_search_slot(trans, root, key, path, -1, 1);
        if (ret < 0)
                goto out;

        BUG_ON(ret != 0);

        ret = btrfs_del_item(trans, root, path);
out:
        btrfs_free_path(path);
        return ret;
}

int btrfs_del_root_ref(struct btrfs_trans_handle *trans,
                       struct btrfs_root *tree_root,
                       u64 root_id, u64 ref_id, u64 dirid, u64 *sequence,
                       const char *name, int name_len)

{
        struct btrfs_path *path;
        struct btrfs_root_ref *ref;
        struct extent_buffer *leaf;
        struct btrfs_key key;
        unsigned long ptr;
        int err = 0;
        int ret;

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

        key.objectid = root_id;
        key.type = BTRFS_ROOT_BACKREF_KEY;
        key.offset = ref_id;
again:
        ret = btrfs_search_slot(trans, tree_root, &key, path, -1, 1);
        BUG_ON(ret < 0);
        if (ret == 0) {
                leaf = path->nodes[0];
                ref = btrfs_item_ptr(leaf, path->slots[0],
                                     struct btrfs_root_ref);

                WARN_ON(btrfs_root_ref_dirid(leaf, ref) != dirid);
                WARN_ON(btrfs_root_ref_name_len(leaf, ref) != name_len);
                ptr = (unsigned long)(ref + 1);
                WARN_ON(memcmp_extent_buffer(leaf, name, ptr, name_len));
                *sequence = btrfs_root_ref_sequence(leaf, ref);

                ret = btrfs_del_item(trans, tree_root, path);
                if (ret) {
                        err = ret;
                        goto out;
                }
        } else
                err = -ENOENT;

        if (key.type == BTRFS_ROOT_BACKREF_KEY) {
                btrfs_release_path(path);
                key.objectid = ref_id;
                key.type = BTRFS_ROOT_REF_KEY;
                key.offset = root_id;
                goto again;
        }

out:
        btrfs_free_path(path);
        return err;
}

/*
 * add a btrfs_root_ref item.  type is either BTRFS_ROOT_REF_KEY
 * or BTRFS_ROOT_BACKREF_KEY.
 *
 * The dirid, sequence, name and name_len refer to the directory entry
 * that is referencing the root.
 *
 * For a forward ref, the root_id is the id of the tree referencing
 * the root and ref_id is the id of the subvol  or snapshot.
 *
 * For a back ref the root_id is the id of the subvol or snapshot and
 * ref_id is the id of the tree referencing it.
 *
 * Will return 0, -ENOMEM, or anything from the CoW path
 */
int btrfs_add_root_ref(struct btrfs_trans_handle *trans,
                       struct btrfs_root *tree_root,
                       u64 root_id, u64 ref_id, u64 dirid, u64 sequence,
                       const char *name, int name_len)
{
        struct btrfs_key key;
        int ret;
        struct btrfs_path *path;
        struct btrfs_root_ref *ref;
        struct extent_buffer *leaf;
        unsigned long ptr;

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

        key.objectid = root_id;
        key.type = BTRFS_ROOT_BACKREF_KEY;
        key.offset = ref_id;
again:
        ret = btrfs_insert_empty_item(trans, tree_root, path, &key,
                                      sizeof(*ref) + name_len);
        if (ret) {
                btrfs_abort_transaction(trans, tree_root, ret);
                btrfs_free_path(path);
                return ret;
        }

        leaf = path->nodes[0];
        ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
        btrfs_set_root_ref_dirid(leaf, ref, dirid);
        btrfs_set_root_ref_sequence(leaf, ref, sequence);
        btrfs_set_root_ref_name_len(leaf, ref, name_len);
        ptr = (unsigned long)(ref + 1);
        write_extent_buffer(leaf, name, ptr, name_len);
        btrfs_mark_buffer_dirty(leaf);

        if (key.type == BTRFS_ROOT_BACKREF_KEY) {
                btrfs_release_path(path);
                key.objectid = ref_id;
                key.type = BTRFS_ROOT_REF_KEY;
                key.offset = root_id;
                goto again;
        }

        btrfs_free_path(path);
        return 0;
}

/*
 * Old btrfs forgets to init root_item->flags and root_item->byte_limit
 * for subvolumes. To work around this problem, we steal a bit from
 * root_item->inode_item->flags, and use it to indicate if those fields
 * have been properly initialized.
 */
void btrfs_check_and_init_root_item(struct btrfs_root_item *root_item)
{
        u64 inode_flags = btrfs_stack_inode_flags(&root_item->inode);

        if (!(inode_flags & BTRFS_INODE_ROOT_ITEM_INIT)) {
                inode_flags |= BTRFS_INODE_ROOT_ITEM_INIT;
                btrfs_set_stack_inode_flags(&root_item->inode, inode_flags);
                btrfs_set_root_flags(root_item, 0);
                btrfs_set_root_limit(root_item, 0);
        }
}

void btrfs_update_root_times(struct btrfs_trans_handle *trans,
                             struct btrfs_root *root)
{
        struct btrfs_root_item *item = &root->root_item;
        struct timespec ct = CURRENT_TIME;

        spin_lock(&root->root_item_lock);
        btrfs_set_root_ctransid(item, trans->transid);
        btrfs_set_stack_timespec_sec(&item->ctime, ct.tv_sec);
        btrfs_set_stack_timespec_nsec(&item->ctime, ct.tv_nsec);
        spin_unlock(&root->root_item_lock);
}