1 files changed, 16 insertions, 89 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index cbd3a7d6fa68..1bcfcdb23cf4 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2769,9 +2769,13 @@ again:
 		 * the commit roots are read only
 		 * so we always do read locks
 		 */
+		if (p->need_commit_sem)
+			down_read(&root->fs_info->commit_root_sem);
 		b = root->commit_root;
 		extent_buffer_get(b);
 		level = btrfs_header_level(b);
+		if (p->need_commit_sem)
+			up_read(&root->fs_info->commit_root_sem);
 		if (!p->skip_locking)
 			btrfs_tree_read_lock(b);
 	} else {
@@ -5360,7 +5364,6 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
 {
 	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;
@@ -5376,9 +5379,8 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
 	int advance_right;
 	u64 left_blockptr;
 	u64 right_blockptr;
-	u64 left_start_ctransid;
-	u64 right_start_ctransid;
-	u64 ctransid;
+	u64 left_gen;
+	u64 right_gen;
 
 	left_path = btrfs_alloc_path();
 	if (!left_path) {
@@ -5402,21 +5404,6 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
 	right_path->search_commit_root = 1;
 	right_path->skip_locking = 1;
 
-	spin_lock(&left_root->root_item_lock);
-	left_start_ctransid = btrfs_root_ctransid(&left_root->root_item);
-	spin_unlock(&left_root->root_item_lock);
-
-	spin_lock(&right_root->root_item_lock);
-	right_start_ctransid = btrfs_root_ctransid(&right_root->root_item);
-	spin_unlock(&right_root->root_item_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
 	 *
@@ -5453,6 +5440,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
 	 *   the right if possible or go up and right.
 	 */
 
+	down_read(&left_root->fs_info->commit_root_sem);
 	left_level = btrfs_header_level(left_root->commit_root);
 	left_root_level = left_level;
 	left_path->nodes[left_level] = left_root->commit_root;
@@ -5462,6 +5450,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
 	right_root_level = right_level;
 	right_path->nodes[right_level] = right_root->commit_root;
 	extent_buffer_get(right_path->nodes[right_level]);
+	up_read(&left_root->fs_info->commit_root_sem);
 
 	if (left_level == 0)
 		btrfs_item_key_to_cpu(left_path->nodes[left_level],
@@ -5480,67 +5469,6 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
 	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_item_lock);
-			ctransid = btrfs_root_ctransid(&left_root->root_item);
-			spin_unlock(&left_root->root_item_lock);
-			if (ctransid != left_start_ctransid)
-				left_start_ctransid = 0;
-
-			spin_lock(&right_root->root_item_lock);
-			ctransid = btrfs_root_ctransid(&right_root->root_item);
-			spin_unlock(&right_root->root_item_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,
@@ -5640,7 +5568,14 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
 				right_blockptr = btrfs_node_blockptr(
 						right_path->nodes[right_level],
 						right_path->slots[right_level]);
-				if (left_blockptr == right_blockptr) {
+				left_gen = btrfs_node_ptr_generation(
+						left_path->nodes[left_level],
+						left_path->slots[left_level]);
+				right_gen = btrfs_node_ptr_generation(
+						right_path->nodes[right_level],
+						right_path->slots[right_level]);
+				if (left_blockptr == right_blockptr &&
+				    left_gen == right_gen) {
 					/*
 					 * As we're on a shared block, don't
 					 * allow to go deeper.
@@ -5663,14 +5598,6 @@ 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;
 }