fs/btrfs/tree-defrag.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2007 Oracle.  All rights reserved.
   4  */
   5
   6 #include <linux/sched.h>
   7 #include "ctree.h"
   8 #include "disk-io.h"
   9 #include "print-tree.h"
  10 #include "transaction.h"
  11 #include "locking.h"
  12
  13 /*
  14  * Defrag all the leaves in a given btree.
  15  * Read all the leaves and try to get key order to
  16  * better reflect disk order
  17  */
  18
  19 int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
  20                         struct btrfs_root *root)
  21 {
  22         struct btrfs_path *path = NULL;
  23         struct btrfs_key key;
  24         int ret = 0;
  25         int wret;
  26         int level;
  27         int next_key_ret = 0;
  28         u64 last_ret = 0;
  29
  30         if (root->fs_info->extent_root == root) {
  31                 /*
  32                  * there's recursion here right now in the tree locking,
  33                  * we can't defrag the extent root without deadlock
  34                  */
  35                 goto out;
  36         }
  37
  38         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
  39                 goto out;
  40
  41         path = btrfs_alloc_path();
  42         if (!path)
  43                 return -ENOMEM;
  44
  45         level = btrfs_header_level(root->node);
  46
  47         if (level == 0)
  48                 goto out;
  49
  50         if (root->defrag_progress.objectid == 0) {
  51                 struct extent_buffer *root_node;
  52                 u32 nritems;
  53
  54                 root_node = btrfs_lock_root_node(root);
  55                 nritems = btrfs_header_nritems(root_node);
  56                 root->defrag_max.objectid = 0;
  57                 /* from above we know this is not a leaf */
  58                 btrfs_node_key_to_cpu(root_node, &root->defrag_max,
  59                                       nritems - 1);
  60                 btrfs_tree_unlock(root_node);
  61                 free_extent_buffer(root_node);
  62                 memset(&key, 0, sizeof(key));
  63         } else {
  64                 memcpy(&key, &root->defrag_progress, sizeof(key));
  65         }
  66
  67         path->keep_locks = 1;
  68
  69         ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION);
  70         if (ret < 0)
  71                 goto out;
  72         if (ret > 0) {
  73                 ret = 0;
  74                 goto out;
  75         }
  76         btrfs_release_path(path);
  77         /*
  78          * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
  79          * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
  80          * a deadlock (attempting to write lock an already write locked leaf).
  81          */
  82         path->lowest_level = 1;
  83         wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
  84
  85         if (wret < 0) {
  86                 ret = wret;
  87                 goto out;
  88         }
  89         if (!path->nodes[1]) {
  90                 ret = 0;
  91                 goto out;
  92         }
  93         /*
  94          * The node at level 1 must always be locked when our path has
  95          * keep_locks set and lowest_level is 1, regardless of the value of
  96          * path->slots[1].
  97          */
  98         BUG_ON(path->locks[1] == 0);
  99         ret = btrfs_realloc_node(trans, root,
 100                                  path->nodes[1], 0,
 101                                  &last_ret,
 102                                  &root->defrag_progress);
 103         if (ret) {
 104                 WARN_ON(ret == -EAGAIN);
 105                 goto out;
 106         }
 107         /*
 108          * Now that we reallocated the node we can find the next key. Note that
 109          * btrfs_find_next_key() can release our path and do another search
 110          * without COWing, this is because even with path->keep_locks = 1,
 111          * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
 112          * node when path->slots[node_level - 1] does not point to the last
 113          * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
 114          * we search for the next key after reallocating our node.
 115          */
 116         path->slots[1] = btrfs_header_nritems(path->nodes[1]);
 117         next_key_ret = btrfs_find_next_key(root, path, &key, 1,
 118                                            BTRFS_OLDEST_GENERATION);
 119         if (next_key_ret == 0) {
 120                 memcpy(&root->defrag_progress, &key, sizeof(key));
 121                 ret = -EAGAIN;
 122         }
 123 out:
 124         btrfs_free_path(path);
 125         if (ret == -EAGAIN) {
 126                 if (root->defrag_max.objectid > root->defrag_progress.objectid)
 127                         goto done;
 128                 if (root->defrag_max.type > root->defrag_progress.type)
 129                         goto done;
 130                 if (root->defrag_max.offset > root->defrag_progress.offset)
 131                         goto done;
 132                 ret = 0;
 133         }
 134 done:
 135         if (ret != -EAGAIN)
 136                 memset(&root->defrag_progress, 0,
 137                        sizeof(root->defrag_progress));
 138
 139         return ret;
 140 }