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
  32 int 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         }
 138 out:
 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         }
 149 done:
 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 }