LXR linux/fs/btrfs/tree-defrag.c

   1/*
   2 * Copyright (C) 2007 Oracle.  All rights reserved.
   3 *
   4 * This program is free software; you can redistribute it and/or
   5 * modify it under the terms of the GNU General Public
   6 * License v2 as published by the Free Software Foundation.
   7 *
   8 * This program is distributed in the hope that it will be useful,
   9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11 * General Public License for more details.
  12 *
  13 * You should have received a copy of the GNU General Public
  14 * License along with this program; if not, write to the
  15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16 * Boston, MA 021110-1307, USA.
  17 */
  18
  19#include <linux/sched.h>
  20#include "ctree.h"
  21#include "disk-io.h"
  22#include "print-tree.h"
  23#include "transaction.h"
  24#include "locking.h"
  25
  26/*
  27 * Defrag all the leaves in a given btree.
  28 * Read all the leaves and try to get key order to
  29 * better reflect disk order
  30 */
  31
  32int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
  33                        struct btrfs_root *root)
  34{
  35        struct btrfs_path *path = NULL;
  36        struct btrfs_key key;
  37        int ret = 0;
  38        int wret;
  39        int level;
  40        int next_key_ret = 0;
  41        u64 last_ret = 0;
  42        u64 min_trans = 0;
  43
  44        if (root->fs_info->extent_root == root) {
  45                /*
  46                 * there's recursion here right now in the tree locking,
  47                 * we can't defrag the extent root without deadlock
  48                 */
  49                goto out;
  50        }
  51
  52        if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
  53                goto out;
  54
  55        path = btrfs_alloc_path();
  56        if (!path)
  57                return -ENOMEM;
  58
  59        level = btrfs_header_level(root->node);
  60
  61        if (level == 0)
  62                goto out;
  63
  64        if (root->defrag_progress.objectid == 0) {
  65                struct extent_buffer *root_node;
  66                u32 nritems;
  67
  68                root_node = btrfs_lock_root_node(root);
  69                btrfs_set_lock_blocking(root_node);
  70                nritems = btrfs_header_nritems(root_node);
  71                root->defrag_max.objectid = 0;
  72                /* from above we know this is not a leaf */
  73                btrfs_node_key_to_cpu(root_node, &root->defrag_max,
  74                                      nritems - 1);
  75                btrfs_tree_unlock(root_node);
  76                free_extent_buffer(root_node);
  77                memset(&key, 0, sizeof(key));
  78        } else {
  79                memcpy(&key, &root->defrag_progress, sizeof(key));
  80        }
  81
  82        path->keep_locks = 1;
  83
  84        ret = btrfs_search_forward(root, &key, path, min_trans);
  85        if (ret < 0)
  86                goto out;
  87        if (ret > 0) {
  88                ret = 0;
  89                goto out;
  90        }
  91        btrfs_release_path(path);
  92        /*
  93         * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
  94         * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
  95         * a deadlock (attempting to write lock an already write locked leaf).
  96         */
  97        path->lowest_level = 1;
  98        wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
  99
 100        if (wret < 0) {
 101                ret = wret;
 102                goto out;
 103        }
 104        if (!path->nodes[1]) {
 105                ret = 0;
 106                goto out;
 107        }
 108        /*
 109         * The node at level 1 must always be locked when our path has
 110         * keep_locks set and lowest_level is 1, regardless of the value of
 111         * path->slots[1].
 112         */
 113        BUG_ON(path->locks[1] == 0);
 114        ret = btrfs_realloc_node(trans, root,
 115                                 path->nodes[1], 0,
 116                                 &last_ret,
 117                                 &root->defrag_progress);
 118        if (ret) {
 119                WARN_ON(ret == -EAGAIN);
 120                goto out;
 121        }
 122        /*
 123         * Now that we reallocated the node we can find the next key. Note that
 124         * btrfs_find_next_key() can release our path and do another search
 125         * without COWing, this is because even with path->keep_locks = 1,
 126         * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
 127         * node when path->slots[node_level - 1] does not point to the last
 128         * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
 129         * we search for the next key after reallocating our node.
 130         */
 131        path->slots[1] = btrfs_header_nritems(path->nodes[1]);
 132        next_key_ret = btrfs_find_next_key(root, path, &key, 1,
 133                                           min_trans);
 134        if (next_key_ret == 0) {
 135                memcpy(&root->defrag_progress, &key, sizeof(key));
 136                ret = -EAGAIN;
 137        }
 138out:
 139        btrfs_free_path(path);
 140        if (ret == -EAGAIN) {
 141                if (root->defrag_max.objectid > root->defrag_progress.objectid)
 142                        goto done;
 143                if (root->defrag_max.type > root->defrag_progress.type)
 144                        goto done;
 145                if (root->defrag_max.offset > root->defrag_progress.offset)
 146                        goto done;
 147                ret = 0;
 148        }
 149done:
 150        if (ret != -EAGAIN) {
 151                memset(&root->defrag_progress, 0,
 152                       sizeof(root->defrag_progress));
 153                root->defrag_trans_start = trans->transid;
 154        }
 155        return ret;
 156}
 157