This walks a btree and reallocates all of the leaves in a more optimal disk
order. It is only triggered by the defrag ioctl today.
Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
diff --git a/fs/btrfs/tree-defrag.c b/fs/btrfs/tree-defrag.c
new file mode 100644
index 0000000..3e8358c
--- /dev/null
+++ b/fs/btrfs/tree-defrag.c
@@ -0,0 +1,147 @@
+/*
+ * Copyright (C) 2007 Oracle. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/sched.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "print-tree.h"
+#include "transaction.h"
+#include "locking.h"
+
+/* defrag all the leaves in a given btree. If cache_only == 1, don't read
+ * things from disk, otherwise read all the leaves and try to get key order to
+ * better reflect disk order
+ */
+
+int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root, int cache_only)
+{
+ struct btrfs_path *path = NULL;
+ struct btrfs_key key;
+ int ret = 0;
+ int wret;
+ int level;
+ int orig_level;
+ int is_extent = 0;
+ int next_key_ret = 0;
+ u64 last_ret = 0;
+ u64 min_trans = 0;
+
+ if (cache_only)
+ goto out;
+
+ if (root->fs_info->extent_root == root) {
+ /*
+ * there's recursion here right now in the tree locking,
+ * we can't defrag the extent root without deadlock
+ */
+ goto out;
+ }
+
+ if (root->ref_cows == 0 && !is_extent)
+ goto out;
+
+ if (btrfs_test_opt(root, SSD))
+ goto out;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+
+ level = btrfs_header_level(root->node);
+ orig_level = level;
+
+ if (level == 0)
+ goto out;
+
+ if (root->defrag_progress.objectid == 0) {
+ struct extent_buffer *root_node;
+ u32 nritems;
+
+ root_node = btrfs_lock_root_node(root);
+ nritems = btrfs_header_nritems(root_node);
+ root->defrag_max.objectid = 0;
+ /* from above we know this is not a leaf */
+ btrfs_node_key_to_cpu(root_node, &root->defrag_max,
+ nritems - 1);
+ btrfs_tree_unlock(root_node);
+ free_extent_buffer(root_node);
+ memset(&key, 0, sizeof(key));
+ } else {
+ memcpy(&key, &root->defrag_progress, sizeof(key));
+ }
+
+ path->keep_locks = 1;
+ if (cache_only)
+ min_trans = root->defrag_trans_start;
+
+ ret = btrfs_search_forward(root, &key, NULL, path,
+ cache_only, min_trans);
+ if (ret < 0)
+ goto out;
+ if (ret > 0) {
+ ret = 0;
+ goto out;
+ }
+ btrfs_release_path(root, path);
+ wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+
+ if (wret < 0) {
+ ret = wret;
+ goto out;
+ }
+ if (!path->nodes[1]) {
+ ret = 0;
+ goto out;
+ }
+ path->slots[1] = btrfs_header_nritems(path->nodes[1]);
+ next_key_ret = btrfs_find_next_key(root, path, &key, 1, cache_only,
+ min_trans);
+ ret = btrfs_realloc_node(trans, root,
+ path->nodes[1], 0,
+ cache_only, &last_ret,
+ &root->defrag_progress);
+ WARN_ON(ret && ret != -EAGAIN);
+ if (next_key_ret == 0) {
+ memcpy(&root->defrag_progress, &key, sizeof(key));
+ ret = -EAGAIN;
+ }
+
+ btrfs_release_path(root, path);
+ if (is_extent)
+ btrfs_extent_post_op(trans, root);
+out:
+ if (path)
+ btrfs_free_path(path);
+ if (ret == -EAGAIN) {
+ if (root->defrag_max.objectid > root->defrag_progress.objectid)
+ goto done;
+ if (root->defrag_max.type > root->defrag_progress.type)
+ goto done;
+ if (root->defrag_max.offset > root->defrag_progress.offset)
+ goto done;
+ ret = 0;
+ }
+done:
+ if (ret != -EAGAIN) {
+ memset(&root->defrag_progress, 0,
+ sizeof(root->defrag_progress));
+ root->defrag_trans_start = trans->transid;
+ }
+ return ret;
+}
--
1.6.0.2
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