LXR linux/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
  19int 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        }
 123out:
 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        }
 134done:
 135        if (ret != -EAGAIN)
 136                memset(&root->defrag_progress, 0,
 137                       sizeof(root->defrag_progress));
 138
 139        return ret;
 140}
 141