return ret;
}
+static void tree_move_down(struct btrfs_root *root,
+ struct btrfs_path *path,
+ int *level, int root_level)
+{
+ path->nodes[*level - 1] = read_node_slot(root, path->nodes[*level],
+ path->slots[*level]);
+ path->slots[*level - 1] = 0;
+ (*level)--;
+}
+
+static int tree_move_next_or_upnext(struct btrfs_root *root,
+ struct btrfs_path *path,
+ int *level, int root_level)
+{
+ int ret = 0;
+ int nritems;
+ nritems = btrfs_header_nritems(path->nodes[*level]);
+
+ path->slots[*level]++;
+
+ while (path->slots[*level] == nritems) {
+ if (*level == root_level)
+ return -1;
+
+ /* move upnext */
+ path->slots[*level] = 0;
+ free_extent_buffer(path->nodes[*level]);
+ path->nodes[*level] = NULL;
+ (*level)++;
+ path->slots[*level]++;
+
+ nritems = btrfs_header_nritems(path->nodes[*level]);
+ ret = 1;
+ }
+ return ret;
+}
+
+/*
+ * Returns 1 if it had to move up and next. 0 is returned if it moved only next
+ * or down.
+ */
+static int tree_advance(struct btrfs_root *root,
+ struct btrfs_path *path,
+ int *level, int root_level,
+ int allow_down,
+ struct btrfs_key *key)
+{
+ int ret;
+
+ if (*level == 0 || !allow_down) {
+ ret = tree_move_next_or_upnext(root, path, level, root_level);
+ } else {
+ tree_move_down(root, path, level, root_level);
+ ret = 0;
+ }
+ if (ret >= 0) {
+ if (*level == 0)
+ btrfs_item_key_to_cpu(path->nodes[*level], key,
+ path->slots[*level]);
+ else
+ btrfs_node_key_to_cpu(path->nodes[*level], key,
+ path->slots[*level]);
+ }
+ return ret;
+}
+
+static int tree_compare_item(struct btrfs_root *left_root,
+ struct btrfs_path *left_path,
+ struct btrfs_path *right_path,
+ char *tmp_buf)
+{
+ int cmp;
+ int len1, len2;
+ unsigned long off1, off2;
+
+ len1 = btrfs_item_size_nr(left_path->nodes[0], left_path->slots[0]);
+ len2 = btrfs_item_size_nr(right_path->nodes[0], right_path->slots[0]);
+ if (len1 != len2)
+ return 1;
+
+ off1 = btrfs_item_ptr_offset(left_path->nodes[0], left_path->slots[0]);
+ off2 = btrfs_item_ptr_offset(right_path->nodes[0],
+ right_path->slots[0]);
+
+ read_extent_buffer(left_path->nodes[0], tmp_buf, off1, len1);
+
+ cmp = memcmp_extent_buffer(right_path->nodes[0], tmp_buf, off2, len1);
+ if (cmp)
+ return 1;
+ return 0;
+}
+
+#define ADVANCE 1
+#define ADVANCE_ONLY_NEXT -1
+
+/*
+ * This function compares two trees and calls the provided callback for
+ * every changed/new/deleted item it finds.
+ * If shared tree blocks are encountered, whole subtrees are skipped, making
+ * the compare pretty fast on snapshotted subvolumes.
+ *
+ * This currently works on commit roots only. As commit roots are read only,
+ * we don't do any locking. The commit roots are protected with transactions.
+ * Transactions are ended and rejoined when a commit is tried in between.
+ *
+ * This function checks for modifications done to the trees while comparing.
+ * If it detects a change, it aborts immediately.
+ */
+int btrfs_compare_trees(struct btrfs_root *left_root,
+ struct btrfs_root *right_root,
+ btrfs_changed_cb_t changed_cb, void *ctx)
+{
+ int ret;
+ int cmp;
+ struct btrfs_trans_handle *trans = NULL;
+ struct btrfs_path *left_path = NULL;
+ struct btrfs_path *right_path = NULL;
+ struct btrfs_key left_key;
+ struct btrfs_key right_key;
+ char *tmp_buf = NULL;
+ int left_root_level;
+ int right_root_level;
+ int left_level;
+ int right_level;
+ int left_end_reached;
+ int right_end_reached;
+ int advance_left;
+ int advance_right;
+ u64 left_blockptr;
+ u64 right_blockptr;
+ u64 left_start_ctransid;
+ u64 right_start_ctransid;
+ u64 ctransid;
+
+ left_path = btrfs_alloc_path();
+ if (!left_path) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ right_path = btrfs_alloc_path();
+ if (!right_path) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ tmp_buf = kmalloc(left_root->leafsize, GFP_NOFS);
+ if (!tmp_buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ left_path->search_commit_root = 1;
+ left_path->skip_locking = 1;
+ right_path->search_commit_root = 1;
+ right_path->skip_locking = 1;
+
+ spin_lock(&left_root->root_times_lock);
+ left_start_ctransid = btrfs_root_ctransid(&left_root->root_item);
+ spin_unlock(&left_root->root_times_lock);
+
+ spin_lock(&right_root->root_times_lock);
+ right_start_ctransid = btrfs_root_ctransid(&right_root->root_item);
+ spin_unlock(&right_root->root_times_lock);
+
+ trans = btrfs_join_transaction(left_root);
+ if (IS_ERR(trans)) {
+ ret = PTR_ERR(trans);
+ trans = NULL;
+ goto out;
+ }
+
+ /*
+ * Strategy: Go to the first items of both trees. Then do
+ *
+ * If both trees are at level 0
+ * Compare keys of current items
+ * If left < right treat left item as new, advance left tree
+ * and repeat
+ * If left > right treat right item as deleted, advance right tree
+ * and repeat
+ * If left == right do deep compare of items, treat as changed if
+ * needed, advance both trees and repeat
+ * If both trees are at the same level but not at level 0
+ * Compare keys of current nodes/leafs
+ * If left < right advance left tree and repeat
+ * If left > right advance right tree and repeat
+ * If left == right compare blockptrs of the next nodes/leafs
+ * If they match advance both trees but stay at the same level
+ * and repeat
+ * If they don't match advance both trees while allowing to go
+ * deeper and repeat
+ * If tree levels are different
+ * Advance the tree that needs it and repeat
+ *
+ * Advancing a tree means:
+ * If we are at level 0, try to go to the next slot. If that's not
+ * possible, go one level up and repeat. Stop when we found a level
+ * where we could go to the next slot. We may at this point be on a
+ * node or a leaf.
+ *
+ * If we are not at level 0 and not on shared tree blocks, go one
+ * level deeper.
+ *
+ * If we are not at level 0 and on shared tree blocks, go one slot to
+ * the right if possible or go up and right.
+ */
+
+ left_level = btrfs_header_level(left_root->commit_root);
+ left_root_level = left_level;
+ left_path->nodes[left_level] = left_root->commit_root;
+ extent_buffer_get(left_path->nodes[left_level]);
+
+ right_level = btrfs_header_level(right_root->commit_root);
+ right_root_level = right_level;
+ right_path->nodes[right_level] = right_root->commit_root;
+ extent_buffer_get(right_path->nodes[right_level]);
+
+ if (left_level == 0)
+ btrfs_item_key_to_cpu(left_path->nodes[left_level],
+ &left_key, left_path->slots[left_level]);
+ else
+ btrfs_node_key_to_cpu(left_path->nodes[left_level],
+ &left_key, left_path->slots[left_level]);
+ if (right_level == 0)
+ btrfs_item_key_to_cpu(right_path->nodes[right_level],
+ &right_key, right_path->slots[right_level]);
+ else
+ btrfs_node_key_to_cpu(right_path->nodes[right_level],
+ &right_key, right_path->slots[right_level]);
+
+ left_end_reached = right_end_reached = 0;
+ advance_left = advance_right = 0;
+
+ while (1) {
+ /*
+ * We need to make sure the transaction does not get committed
+ * while we do anything on commit roots. This means, we need to
+ * join and leave transactions for every item that we process.
+ */
+ if (trans && btrfs_should_end_transaction(trans, left_root)) {
+ btrfs_release_path(left_path);
+ btrfs_release_path(right_path);
+
+ ret = btrfs_end_transaction(trans, left_root);
+ trans = NULL;
+ if (ret < 0)
+ goto out;
+ }
+ /* now rejoin the transaction */
+ if (!trans) {
+ trans = btrfs_join_transaction(left_root);
+ if (IS_ERR(trans)) {
+ ret = PTR_ERR(trans);
+ trans = NULL;
+ goto out;
+ }
+
+ spin_lock(&left_root->root_times_lock);
+ ctransid = btrfs_root_ctransid(&left_root->root_item);
+ spin_unlock(&left_root->root_times_lock);
+ if (ctransid != left_start_ctransid)
+ left_start_ctransid = 0;
+
+ spin_lock(&right_root->root_times_lock);
+ ctransid = btrfs_root_ctransid(&right_root->root_item);
+ spin_unlock(&right_root->root_times_lock);
+ if (ctransid != right_start_ctransid)
+ right_start_ctransid = 0;
+
+ if (!left_start_ctransid || !right_start_ctransid) {
+ WARN(1, KERN_WARNING
+ "btrfs: btrfs_compare_tree detected "
+ "a change in one of the trees while "
+ "iterating. This is probably a "
+ "bug.\n");
+ ret = -EIO;
+ goto out;
+ }
+
+ /*
+ * the commit root may have changed, so start again
+ * where we stopped
+ */
+ left_path->lowest_level = left_level;
+ right_path->lowest_level = right_level;
+ ret = btrfs_search_slot(NULL, left_root,
+ &left_key, left_path, 0, 0);
+ if (ret < 0)
+ goto out;
+ ret = btrfs_search_slot(NULL, right_root,
+ &right_key, right_path, 0, 0);
+ if (ret < 0)
+ goto out;
+ }
+
+ if (advance_left && !left_end_reached) {
+ ret = tree_advance(left_root, left_path, &left_level,
+ left_root_level,
+ advance_left != ADVANCE_ONLY_NEXT,
+ &left_key);
+ if (ret < 0)
+ left_end_reached = ADVANCE;
+ advance_left = 0;
+ }
+ if (advance_right && !right_end_reached) {
+ ret = tree_advance(right_root, right_path, &right_level,
+ right_root_level,
+ advance_right != ADVANCE_ONLY_NEXT,
+ &right_key);
+ if (ret < 0)
+ right_end_reached = ADVANCE;
+ advance_right = 0;
+ }
+
+ if (left_end_reached && right_end_reached) {
+ ret = 0;
+ goto out;
+ } else if (left_end_reached) {
+ if (right_level == 0) {
+ ret = changed_cb(left_root, right_root,
+ left_path, right_path,
+ &right_key,
+ BTRFS_COMPARE_TREE_DELETED,
+ ctx);
+ if (ret < 0)
+ goto out;
+ }
+ advance_right = ADVANCE;
+ continue;
+ } else if (right_end_reached) {
+ if (left_level == 0) {
+ ret = changed_cb(left_root, right_root,
+ left_path, right_path,
+ &left_key,
+ BTRFS_COMPARE_TREE_NEW,
+ ctx);
+ if (ret < 0)
+ goto out;
+ }
+ advance_left = ADVANCE;
+ continue;
+ }
+
+ if (left_level == 0 && right_level == 0) {
+ cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
+ if (cmp < 0) {
+ ret = changed_cb(left_root, right_root,
+ left_path, right_path,
+ &left_key,
+ BTRFS_COMPARE_TREE_NEW,
+ ctx);
+ if (ret < 0)
+ goto out;
+ advance_left = ADVANCE;
+ } else if (cmp > 0) {
+ ret = changed_cb(left_root, right_root,
+ left_path, right_path,
+ &right_key,
+ BTRFS_COMPARE_TREE_DELETED,
+ ctx);
+ if (ret < 0)
+ goto out;
+ advance_right = ADVANCE;
+ } else {
+ ret = tree_compare_item(left_root, left_path,
+ right_path, tmp_buf);
+ if (ret) {
+ ret = changed_cb(left_root, right_root,
+ left_path, right_path,
+ &left_key,
+ BTRFS_COMPARE_TREE_CHANGED,
+ ctx);
+ if (ret < 0)
+ goto out;
+ }
+ advance_left = ADVANCE;
+ advance_right = ADVANCE;
+ }
+ } else if (left_level == right_level) {
+ cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
+ if (cmp < 0) {
+ advance_left = ADVANCE;
+ } else if (cmp > 0) {
+ advance_right = ADVANCE;
+ } else {
+ left_blockptr = btrfs_node_blockptr(
+ left_path->nodes[left_level],
+ left_path->slots[left_level]);
+ right_blockptr = btrfs_node_blockptr(
+ right_path->nodes[right_level],
+ right_path->slots[right_level]);
+ if (left_blockptr == right_blockptr) {
+ /*
+ * As we're on a shared block, don't
+ * allow to go deeper.
+ */
+ advance_left = ADVANCE_ONLY_NEXT;
+ advance_right = ADVANCE_ONLY_NEXT;
+ } else {
+ advance_left = ADVANCE;
+ advance_right = ADVANCE;
+ }
+ }
+ } else if (left_level < right_level) {
+ advance_right = ADVANCE;
+ } else {
+ advance_left = ADVANCE;
+ }
+ }
+
+out:
+ btrfs_free_path(left_path);
+ btrfs_free_path(right_path);
+ kfree(tmp_buf);
+
+ if (trans) {
+ if (!ret)
+ ret = btrfs_end_transaction(trans, left_root);
+ else
+ btrfs_end_transaction(trans, left_root);
+ }
+
+ return ret;
+}
+
/*
* this is similar to btrfs_next_leaf, but does not try to preserve
* and fixup the path. It looks for and returns the next key in the
projects / firefly-linux-kernel-4.4.55.git / commitdiff