tree-defrag.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/sched.h>
#include "ctree.h"
#include "disk-io.h"
#include "print-tree.h"
#include "transaction.h"
#include "locking.h"

/* defrag all the leaves in a given btree.  If cache_only == 1, don't read
 * things from disk, otherwise read all the leaves and try to get key order to
 * better reflect disk order
 */

int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
            struct btrfs_root *root, int cache_only)
{
    struct btrfs_path *path = NULL;
    struct btrfs_key key;
    int ret = 0;
    int wret;
    int level;
    int is_extent = 0;
    int next_key_ret = 0;
    u64 last_ret = 0;
    u64 min_trans = 0;

    if (cache_only)
        goto out;

    if (root->fs_info->extent_root == root) {
        /*
         * there's recursion here right now in the tree locking,
         * we can't defrag the extent root without deadlock
         */
        goto out;
    }

    if (root->ref_cows == 0 && !is_extent)
        goto out;

    if (btrfs_test_opt(root, SSD))
        goto out;

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

    level = btrfs_header_level(root->node);

    if (level == 0)
        goto out;

    if (root->defrag_progress.objectid == 0) {
        struct extent_buffer *root_node;
        u32 nritems;

        root_node = btrfs_lock_root_node(root);
        btrfs_set_lock_blocking(root_node);
        nritems = btrfs_header_nritems(root_node);
        root->defrag_max.objectid = 0;
        /* from above we know this is not a leaf */
        btrfs_node_key_to_cpu(root_node, &root->defrag_max,
                      nritems - 1);
        btrfs_tree_unlock(root_node);
        free_extent_buffer(root_node);
        memset(&key, 0, sizeof(key));
    } else {
        memcpy(&key, &root->defrag_progress, sizeof(key));
    }

    path->keep_locks = 1;
    if (cache_only)
        min_trans = root->defrag_trans_start;

    ret = btrfs_search_forward(root, &key, NULL, path,
                   cache_only, min_trans);
    if (ret < 0)
        goto out;
    if (ret > 0) {
        ret = 0;
        goto out;
    }
    btrfs_release_path(path);
    wret = btrfs_search_slot(trans, root, &key, path, 0, 1);

    if (wret < 0) {
        ret = wret;
        goto out;
    }
    if (!path->nodes[1]) {
        ret = 0;
        goto out;
    }
    path->slots[1] = btrfs_header_nritems(path->nodes[1]);
    next_key_ret = btrfs_find_next_key(root, path, &key, 1, cache_only,
                       min_trans);
    ret = btrfs_realloc_node(trans, root,
                 path->nodes[1], 0,
                 cache_only, &last_ret,
                 &root->defrag_progress);
    if (ret) {
        WARN_ON(ret == -EAGAIN);
        goto out;
    }
    if (next_key_ret == 0) {
        memcpy(&root->defrag_progress, &key, sizeof(key));
        ret = -EAGAIN;
    }
out:
    if (path)
        btrfs_free_path(path);
    if (ret == -EAGAIN) {
        if (root->defrag_max.objectid > root->defrag_progress.objectid)
            goto done;
        if (root->defrag_max.type > root->defrag_progress.type)
            goto done;
        if (root->defrag_max.offset > root->defrag_progress.offset)
            goto done;
        ret = 0;
    }
done:
    if (ret != -EAGAIN) {
        memset(&root->defrag_progress, 0,
               sizeof(root->defrag_progress));
        root->defrag_trans_start = trans->transid;
    }
    return ret;
}