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_REF_COWS, &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                btrfs_set_lock_blocking(root_node);
  56                nritems = btrfs_header_nritems(root_node);
  57                root->defrag_max.objectid = 0;
  58                /* from above we know this is not a leaf */
  59                btrfs_node_key_to_cpu(root_node, &root->defrag_max,
  60                                      nritems - 1);
  61                btrfs_tree_unlock(root_node);
  62                free_extent_buffer(root_node);
  63                memset(&key, 0, sizeof(key));
  64        } else {
  65                memcpy(&key, &root->defrag_progress, sizeof(key));
  66        }
  67
  68        path->keep_locks = 1;
  69
  70        ret = btrfs_search_forward(root, &key, path, BTRFS_OLDEST_GENERATION);
  71        if (ret < 0)
  72                goto out;
  73        if (ret > 0) {
  74                ret = 0;
  75                goto out;
  76        }
  77        btrfs_release_path(path);
  78        /*
  79         * We don't need a lock on a leaf. btrfs_realloc_node() will lock all
  80         * leafs from path->nodes[1], so set lowest_level to 1 to avoid later
  81         * a deadlock (attempting to write lock an already write locked leaf).
  82         */
  83        path->lowest_level = 1;
  84        wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
  85
  86        if (wret < 0) {
  87                ret = wret;
  88                goto out;
  89        }
  90        if (!path->nodes[1]) {
  91                ret = 0;
  92                goto out;
  93        }
  94        /*
  95         * The node at level 1 must always be locked when our path has
  96         * keep_locks set and lowest_level is 1, regardless of the value of
  97         * path->slots[1].
  98         */
  99        BUG_ON(path->locks[1] == 0);
 100        ret = btrfs_realloc_node(trans, root,
 101                                 path->nodes[1], 0,
 102                                 &last_ret,
 103                                 &root->defrag_progress);
 104        if (ret) {
 105                WARN_ON(ret == -EAGAIN);
 106                goto out;
 107        }
 108        /*
 109         * Now that we reallocated the node we can find the next key. Note that
 110         * btrfs_find_next_key() can release our path and do another search
 111         * without COWing, this is because even with path->keep_locks = 1,
 112         * btrfs_search_slot() / ctree.c:unlock_up() does not keeps a lock on a
 113         * node when path->slots[node_level - 1] does not point to the last
 114         * item or a slot beyond the last item (ctree.c:unlock_up()). Therefore
 115         * we search for the next key after reallocating our node.
 116         */
 117        path->slots[1] = btrfs_header_nritems(path->nodes[1]);
 118        next_key_ret = btrfs_find_next_key(root, path, &key, 1,
 119                                           BTRFS_OLDEST_GENERATION);
 120        if (next_key_ret == 0) {
 121                memcpy(&root->defrag_progress, &key, sizeof(key));
 122                ret = -EAGAIN;
 123        }
 124out:
 125        btrfs_free_path(path);
 126        if (ret == -EAGAIN) {
 127                if (root->defrag_max.objectid > root->defrag_progress.objectid)
 128                        goto done;
 129                if (root->defrag_max.type > root->defrag_progress.type)
 130                        goto done;
 131                if (root->defrag_max.offset > root->defrag_progress.offset)
 132                        goto done;
 133                ret = 0;
 134        }
 135done:
 136        if (ret != -EAGAIN) {
 137                memset(&root->defrag_progress, 0,
 138                       sizeof(root->defrag_progress));
 139                root->defrag_trans_start = trans->transid;
 140        }
 141        return ret;
 142}
 143