1 files changed, 6 insertions, 88 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 88d1b1eedc9c..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;
@@ -5378,9 +5381,6 @@ int btrfs_compare_trees(struct btrfs_root *left_root,
         u64 right_blockptr;
         u64 left_gen;
         u64 right_gen;
-        u64 left_start_ctransid;
-        u64 right_start_ctransid;
-        u64 ctransid;
 
         left_path = btrfs_alloc_path();
         if (!left_path) {
@@ -5404,21 +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
          *
@@ -5455,6 +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;
@@ -5464,6 +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],
@@ -5482,67 +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,
@@ -5672,14 +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;
 }