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 (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
  31                goto out;
  32
  33        path = btrfs_alloc_path();
  34        if (!path)
  35                return -ENOMEM;
  36
  37        level = btrfs_header_level(root->node);
  38
  39        if (level == 0)
  40                goto out;
  41
  42        if (root->defrag_progress.objectid == 0) {
  43                struct extent_buffer *root_node;
  44                u32 nritems;
  45
  46                root_node = btrfs_lock_root_node(root);
  47                nritems = btrfs_header_nritems(root_node);
  48                root->defrag_max.objectid = 0;
  49                /* from above we know this is not a leaf */
  50                btrfs_node_key_to_cpu(root_node, &root->defrag_max,
  51                                      nritems - 1);
  52                btrfs_tree_unlock(root_node);
  53                free_extent_buffer(root_node);
  54                memset(&key, 0, sizeof(key));
  55        } else {
  56                memcpy(&key, &root->defrag_progress, sizeof(key));
  57        }
  58
  59        path->keep_locks = 1;
  60
  61        ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION);
  62        if (ret < 0)
  63                goto out;
  64        if (ret > 0) {
  65                ret = 0;
  66                goto out;
  67        }
  68        btrfs_release_path(path);
  69        /*
  70         * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
  71         * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
  72         * a deadlock (attempting to write lock an already write locked leaf).
  73         */
  74        path->lowest_level = 1;
  75        wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
  76
  77        if (wret < 0) {
  78                ret = wret;
  79                goto out;
  80        }
  81        if (!path->nodes[1]) {
  82                ret = 0;
  83                goto out;
  84        }
  85        /*
  86         * The node at level 1 must always be locked when our path has
  87         * keep_locks set and lowest_level is 1, regardless of the value of
  88         * path->slots[1].
  89         */
  90        BUG_ON(path->locks[1] == 0);
  91        ret = btrfs_realloc_node(trans, root,
  92                                 path->nodes[1], 0,
  93                                 &last_ret,
  94                                 &root->defrag_progress);
  95        if (ret) {
  96                WARN_ON(ret == -EAGAIN);
  97                goto out;
  98        }
  99        /*
 100         * Now that we reallocated the node we can find the next key. Note that
 101         * btrfs_find_next_key() can release our path and do another search
 102         * without COWing, this is because even with path->keep_locks = 1,
 103         * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
 104         * node when path->slots[node_level - 1] does not point to the last
 105         * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
 106         * we search for the next key after reallocating our node.
 107         */
 108        path->slots[1] = btrfs_header_nritems(path->nodes[1]);
 109        next_key_ret = btrfs_find_next_key(root, path, &key, 1,
 110                                           BTRFS_OLDEST_GENERATION);
 111        if (next_key_ret == 0) {
 112                memcpy(&root->defrag_progress, &key, sizeof(key));
 113                ret = -EAGAIN;
 114        }
 115out:
 116        btrfs_free_path(path);
 117        if (ret == -EAGAIN) {
 118                if (root->defrag_max.objectid > root->defrag_progress.objectid)
 119                        goto done;
 120                if (root->defrag_max.type > root->defrag_progress.type)
 121                        goto done;
 122                if (root->defrag_max.offset > root->defrag_progress.offset)
 123                        goto done;
 124                ret = 0;
 125        }
 126done:
 127        if (ret != -EAGAIN)
 128                memset(&root->defrag_progress, 0,
 129                       sizeof(root->defrag_progress));
 130
 131        return ret;
 132}
 133