root-tree.c

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/*
 * 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/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.
 */
void btrfs_read_root_item(struct btrfs_root *root,
             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);
    }
}

/*
 * lookup the root with the highest offset for a given objectid.  The key we do
 * find is copied into 'key'.  If we find something return 0, otherwise 1, < 0
 * on error.
 */
int btrfs_find_last_root(struct btrfs_root *root, u64 objectid,
            struct btrfs_root_item *item, struct btrfs_key *key)
{
    struct btrfs_path *path;
    struct btrfs_key search_key;
    struct btrfs_key found_key;
    struct extent_buffer *l;
    int ret;
    int slot;

    search_key.objectid = objectid;
    search_key.type = BTRFS_ROOT_ITEM_KEY;
    search_key.offset = (u64)-1;

    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;
    ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
    if (ret < 0)
        goto out;

    BUG_ON(ret == 0);
    if (path->slots[0] == 0) {
        ret = 1;
        goto out;
    }
    l = path->nodes[0];
    slot = path->slots[0] - 1;
    btrfs_item_key_to_cpu(l, &found_key, slot);
    if (found_key.objectid != objectid ||
        found_key.type != BTRFS_ROOT_ITEM_KEY) {
        ret = 1;
        goto out;
    }
    if (item)
        btrfs_read_root_item(root, l, slot, item);
    if (key)
        memcpy(key, &found_key, sizeof(found_key));

    ret = 0;
out:
    btrfs_free_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]);
        printk(KERN_CRIT "unable to update root key %llu %u %llu\n",
               (unsigned long long)key->objectid, key->type,
               (unsigned long long)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));
}

/*
 * at mount time we want to find all the old transaction snapshots that were in
 * the process of being deleted if we crashed.  This is any root item with an
 * offset lower than the latest root.  They need to be queued for deletion to
 * finish what was happening when we crashed.
 */
int btrfs_find_dead_roots(struct btrfs_root *root, u64 objectid)
{
    struct btrfs_root *dead_root;
    struct btrfs_root_item *ri;
    struct btrfs_key key;
    struct btrfs_key found_key;
    struct btrfs_path *path;
    int ret;
    u32 nritems;
    struct extent_buffer *leaf;
    int slot;

    key.objectid = objectid;
    btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
    key.offset = 0;
    path = btrfs_alloc_path();
    if (!path)
        return -ENOMEM;

again:
    ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
    if (ret < 0)
        goto err;
    while (1) {
        leaf = path->nodes[0];
        nritems = btrfs_header_nritems(leaf);
        slot = path->slots[0];
        if (slot >= nritems) {
            ret = btrfs_next_leaf(root, path);
            if (ret)
                break;
            leaf = path->nodes[0];
            nritems = btrfs_header_nritems(leaf);
            slot = path->slots[0];
        }
        btrfs_item_key_to_cpu(leaf, &key, slot);
        if (btrfs_key_type(&key) != BTRFS_ROOT_ITEM_KEY)
            goto next;

        if (key.objectid < objectid)
            goto next;

        if (key.objectid > objectid)
            break;

        ri = btrfs_item_ptr(leaf, slot, struct btrfs_root_item);
        if (btrfs_disk_root_refs(leaf, ri) != 0)
            goto next;

        memcpy(&found_key, &key, sizeof(key));
        key.offset++;
        btrfs_release_path(path);
        dead_root =
            btrfs_read_fs_root_no_radix(root->fs_info->tree_root,
                            &found_key);
        if (IS_ERR(dead_root)) {
            ret = PTR_ERR(dead_root);
            goto err;
        }

        ret = btrfs_add_dead_root(dead_root);
        if (ret)
            goto err;
        goto again;
next:
        slot++;
        path->slots[0]++;
    }
    ret = 0;
err:
    btrfs_free_path(path);
    return ret;
}

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;

    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_no_name(tree_root->fs_info,
                          &root_key);
        if (!IS_ERR(root))
            continue;

        ret = PTR_ERR(root);
        if (ret != -ENOENT) {
            err = ret;
            break;
        }

        ret = btrfs_find_dead_roots(tree_root, root_key.objectid);
        if (ret) {
            err = ret;
            break;
        }
    }

    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;
    struct btrfs_root_item *ri;
    struct extent_buffer *leaf;

    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);
    leaf = path->nodes[0];
    ri = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_item);

    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;
}

int btrfs_find_root_ref(struct btrfs_root *tree_root,
           struct btrfs_path *path,
           u64 root_id, u64 ref_id)
{
    struct btrfs_key key;
    int ret;

    key.objectid = root_id;
    key.type = BTRFS_ROOT_REF_KEY;
    key.offset = ref_id;

    ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
    return ret;
}

/*
 * 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 = le64_to_cpu(root_item->inode.flags);

    if (!(inode_flags & BTRFS_INODE_ROOT_ITEM_INIT)) {
        inode_flags |= BTRFS_INODE_ROOT_ITEM_INIT;
        root_item->inode.flags = cpu_to_le64(inode_flags);
        root_item->flags = 0;
        root_item->byte_limit = 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_times_lock);
    item->ctransid = cpu_to_le64(trans->transid);
    item->ctime.sec = cpu_to_le64(ct.tv_sec);
    item->ctime.nsec = cpu_to_le32(ct.tv_nsec);
    spin_unlock(&root->root_times_lock);
}