9 files changed, 77 insertions, 187 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index aad7201..10db21f 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -330,7 +330,10 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 		goto out;
 	}
 
-	root_level = btrfs_old_root_level(root, time_seq);
+	if (path->search_commit_root)
+		root_level = btrfs_header_level(root->commit_root);
+	else
+		root_level = btrfs_old_root_level(root, time_seq);
 
 	if (root_level + 1 == level) {
 		srcu_read_unlock(&fs_info->subvol_srcu, index);
@@ -1099,9 +1102,9 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
  *
  * returns 0 on success, < 0 on error.
  */
-int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
-				struct btrfs_fs_info *fs_info, u64 bytenr,
-				u64 time_seq, struct ulist **roots)
+static int __btrfs_find_all_roots(struct btrfs_trans_handle *trans,
+				  struct btrfs_fs_info *fs_info, u64 bytenr,
+				  u64 time_seq, struct ulist **roots)
 {
 	struct ulist *tmp;
 	struct ulist_node *node = NULL;
@@ -1137,6 +1140,20 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
+int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
+			 struct btrfs_fs_info *fs_info, u64 bytenr,
+			 u64 time_seq, struct ulist **roots)
+{
+	int ret;
+
+	if (!trans)
+		down_read(&fs_info->commit_root_sem);
+	ret = __btrfs_find_all_roots(trans, fs_info, bytenr, time_seq, roots);
+	if (!trans)
+		up_read(&fs_info->commit_root_sem);
+	return ret;
+}
+
 /*
  * this makes the path point to (inum INODE_ITEM ioff)
  */
@@ -1516,6 +1533,8 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
 		if (IS_ERR(trans))
 			return PTR_ERR(trans);
 		btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
+	} else {
+		down_read(&fs_info->commit_root_sem);
 	}
 
 	ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
@@ -1526,8 +1545,8 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
 
 	ULIST_ITER_INIT(&ref_uiter);
 	while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
-		ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
-					   tree_mod_seq_elem.seq, &roots);
+		ret = __btrfs_find_all_roots(trans, fs_info, ref_node->val,
+					     tree_mod_seq_elem.seq, &roots);
 		if (ret)
 			break;
 		ULIST_ITER_INIT(&root_uiter);
@@ -1549,6 +1568,8 @@ out:
 	if (!search_commit_root) {
 		btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
 		btrfs_end_transaction(trans, fs_info->extent_root);
+	} else {
+		up_read(&fs_info->commit_root_sem);
 	}
 
 	return ret;
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 88d1b1e..9d89c16 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -5360,7 +5360,6 @@ 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 +5377,6 @@ 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 +5400,6 @@ 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
 	 *
@@ -5482,67 +5463,6 @@ 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 +5592,6 @@ 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;
 }
 
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 2a9d32e..4253ab2 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1440,7 +1440,7 @@ struct btrfs_fs_info {
 	 */
 	struct mutex ordered_extent_flush_mutex;
 
-	struct rw_semaphore extent_commit_sem;
+	struct rw_semaphore commit_root_sem;
 
 	struct rw_semaphore cleanup_work_sem;
 
@@ -1711,7 +1711,6 @@ struct btrfs_root {
 	struct btrfs_block_rsv *block_rsv;
 
 	/* free ino cache stuff */
-	struct mutex fs_commit_mutex;
 	struct btrfs_free_space_ctl *free_ino_ctl;
 	enum btrfs_caching_type cached;
 	spinlock_t cache_lock;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 98fe701..6d1ac7d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1567,7 +1567,6 @@ int btrfs_init_fs_root(struct btrfs_root *root)
 	root->subv_writers = writers;
 
 	btrfs_init_free_ino_ctl(root);
-	mutex_init(&root->fs_commit_mutex);
 	spin_lock_init(&root->cache_lock);
 	init_waitqueue_head(&root->cache_wait);
 
@@ -2345,7 +2344,7 @@ int open_ctree(struct super_block *sb,
 	mutex_init(&fs_info->transaction_kthread_mutex);
 	mutex_init(&fs_info->cleaner_mutex);
 	mutex_init(&fs_info->volume_mutex);
-	init_rwsem(&fs_info->extent_commit_sem);
+	init_rwsem(&fs_info->commit_root_sem);
 	init_rwsem(&fs_info->cleanup_work_sem);
 	init_rwsem(&fs_info->subvol_sem);
 	sema_init(&fs_info->uuid_tree_rescan_sem, 1);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e09db2c..4d2508b 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -419,7 +419,7 @@ static noinline void caching_thread(struct btrfs_work *work)
 again:
 	mutex_lock(&caching_ctl->mutex);
 	/* need to make sure the commit_root doesn't disappear */
-	down_read(&fs_info->extent_commit_sem);
+	down_read(&fs_info->commit_root_sem);
 
 next:
 	ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
@@ -443,10 +443,10 @@ next:
 				break;
 
 			if (need_resched() ||
-			    rwsem_is_contended(&fs_info->extent_commit_sem)) {
+			    rwsem_is_contended(&fs_info->commit_root_sem)) {
 				caching_ctl->progress = last;
 				btrfs_release_path(path);
-				up_read(&fs_info->extent_commit_sem);
+				up_read(&fs_info->commit_root_sem);
 				mutex_unlock(&caching_ctl->mutex);
 				cond_resched();
 				goto again;
@@ -513,7 +513,7 @@ next:
 
 err:
 	btrfs_free_path(path);
-	up_read(&fs_info->extent_commit_sem);
+	up_read(&fs_info->commit_root_sem);
 
 	free_excluded_extents(extent_root, block_group);
 
@@ -633,10 +633,10 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
 		return 0;
 	}
 
-	down_write(&fs_info->extent_commit_sem);
+	down_write(&fs_info->commit_root_sem);
 	atomic_inc(&caching_ctl->count);
 	list_add_tail(&caching_ctl->list, &fs_info->caching_block_groups);
-	up_write(&fs_info->extent_commit_sem);
+	up_write(&fs_info->commit_root_sem);
 
 	btrfs_get_block_group(cache);
 
@@ -5471,7 +5471,7 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
 	struct btrfs_block_group_cache *cache;
 	struct btrfs_space_info *space_info;
 
-	down_write(&fs_info->extent_commit_sem);
+	down_write(&fs_info->commit_root_sem);
 
 	list_for_each_entry_safe(caching_ctl, next,
 				 &fs_info->caching_block_groups, list) {
@@ -5490,7 +5490,7 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
 	else
 		fs_info->pinned_extents = &fs_info->freed_extents[0];
 
-	up_write(&fs_info->extent_commit_sem);
+	up_write(&fs_info->commit_root_sem);
 
 	list_for_each_entry_rcu(space_info, &fs_info->space_info, list)
 		percpu_counter_set(&space_info->total_bytes_pinned, 0);
@@ -8256,14 +8256,14 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info)
 	struct btrfs_caching_control *caching_ctl;
 	struct rb_node *n;
 
-	down_write(&info->extent_commit_sem);
+	down_write(&info->commit_root_sem);
 	while (!list_empty(&info->caching_block_groups)) {
 		caching_ctl = list_entry(info->caching_block_groups.next,
 					 struct btrfs_caching_control, list);
 		list_del(&caching_ctl->list);
 		put_caching_control(caching_ctl);
 	}
-	up_write(&info->extent_commit_sem);
+	up_write(&info->commit_root_sem);
 
 	spin_lock(&info->block_group_cache_lock);
 	while ((n = rb_last(&info->block_group_cache_tree)) != NULL) {
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index ab485e5..cc8ca193 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -55,7 +55,7 @@ static int caching_kthread(void *data)
 	key.type = BTRFS_INODE_ITEM_KEY;
 again:
 	/* need to make sure the commit_root doesn't disappear */
-	mutex_lock(&root->fs_commit_mutex);
+	down_read(&fs_info->commit_root_sem);
 
 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 	if (ret < 0)
@@ -88,7 +88,7 @@ again:
 				btrfs_item_key_to_cpu(leaf, &key, 0);
 				btrfs_release_path(path);
 				root->cache_progress = last;
-				mutex_unlock(&root->fs_commit_mutex);
+				up_read(&fs_info->commit_root_sem);
 				schedule_timeout(1);
 				goto again;
 			} else
@@ -127,7 +127,7 @@ next:
 	btrfs_unpin_free_ino(root);
 out:
 	wake_up(&root->cache_wait);
-	mutex_unlock(&root->fs_commit_mutex);
+	up_read(&fs_info->commit_root_sem);
 
 	btrfs_free_path(path);
 
@@ -223,11 +223,11 @@ again:
 		 * or the caching work is done.
 		 */
 
-		mutex_lock(&root->fs_commit_mutex);
+		down_write(&root->fs_info->commit_root_sem);
 		spin_lock(&root->cache_lock);
 		if (root->cached == BTRFS_CACHE_FINISHED) {
 			spin_unlock(&root->cache_lock);
-			mutex_unlock(&root->fs_commit_mutex);
+			up_write(&root->fs_info->commit_root_sem);
 			goto again;
 		}
 		spin_unlock(&root->cache_lock);
@@ -240,7 +240,7 @@ again:
 		else
 			__btrfs_add_free_space(pinned, objectid, 1);
 
-		mutex_unlock(&root->fs_commit_mutex);
+		up_write(&root->fs_info->commit_root_sem);
 	}
 }
 
@@ -250,7 +250,7 @@ again:
  * and others will just be dropped, because the commit root we were
  * searching has changed.
  *
- * Must be called with root->fs_commit_mutex held
+ * Must be called with root->fs_info->commit_root_sem held
  */
 void btrfs_unpin_free_ino(struct btrfs_root *root)
 {
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index d00534b..6b5f136 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -1268,8 +1268,10 @@ static int find_extent_clone(struct send_ctx *sctx,
 	}
 	logical = disk_byte + btrfs_file_extent_offset(eb, fi);
 
+	down_read(&sctx->send_root->fs_info->commit_root_sem);
 	ret = extent_from_logical(sctx->send_root->fs_info, disk_byte, tmp_path,
 				  &found_key, &flags);
+	up_read(&sctx->send_root->fs_info->commit_root_sem);
 	btrfs_release_path(tmp_path);
 
 	if (ret < 0)
@@ -5367,57 +5369,21 @@ out:
 static int full_send_tree(struct send_ctx *sctx)
 {
 	int ret;
-	struct btrfs_trans_handle *trans = NULL;
 	struct btrfs_root *send_root = sctx->send_root;
 	struct btrfs_key key;
 	struct btrfs_key found_key;
 	struct btrfs_path *path;
 	struct extent_buffer *eb;
 	int slot;
-	u64 start_ctransid;
-	u64 ctransid;
 
 	path = alloc_path_for_send();
 	if (!path)
 		return -ENOMEM;
 
-	spin_lock(&send_root->root_item_lock);
-	start_ctransid = btrfs_root_ctransid(&send_root->root_item);
-	spin_unlock(&send_root->root_item_lock);
-
 	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
 	key.type = BTRFS_INODE_ITEM_KEY;
 	key.offset = 0;
 
-join_trans:
-	/*
-	 * We need to make sure the transaction does not get committed
-	 * while we do anything on commit roots. Join a transaction to prevent
-	 * this.
-	 */
-	trans = btrfs_join_transaction(send_root);
-	if (IS_ERR(trans)) {
-		ret = PTR_ERR(trans);
-		trans = NULL;
-		goto out;
-	}
-
-	/*
-	 * Make sure the tree has not changed after re-joining. We detect this
-	 * by comparing start_ctransid and ctransid. They should always match.
-	 */
-	spin_lock(&send_root->root_item_lock);
-	ctransid = btrfs_root_ctransid(&send_root->root_item);
-	spin_unlock(&send_root->root_item_lock);
-
-	if (ctransid != start_ctransid) {
-		WARN(1, KERN_WARNING "BTRFS: the root that you're trying to "
-				     "send was modified in between. This is "
-				     "probably a bug.\n");
-		ret = -EIO;
-		goto out;
-	}
-
 	ret = btrfs_search_slot_for_read(send_root, &key, path, 1, 0);
 	if (ret < 0)
 		goto out;
@@ -5425,19 +5391,6 @@ join_trans:
 		goto out_finish;
 
 	while (1) {
-		/*
-		 * When someone want to commit while we iterate, end the
-		 * joined transaction and rejoin.
-		 */
-		if (btrfs_should_end_transaction(trans, send_root)) {
-			ret = btrfs_end_transaction(trans, send_root);
-			trans = NULL;
-			if (ret < 0)
-				goto out;
-			btrfs_release_path(path);
-			goto join_trans;
-		}
-
 		eb = path->nodes[0];
 		slot = path->slots[0];
 		btrfs_item_key_to_cpu(eb, &found_key, slot);
@@ -5465,12 +5418,6 @@ out_finish:
 
 out:
 	btrfs_free_path(path);
-	if (trans) {
-		if (!ret)
-			ret = btrfs_end_transaction(trans, send_root);
-		else
-			btrfs_end_transaction(trans, send_root);
-	}
 	return ret;
 }
 
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 038177c..7579f6d 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -75,10 +75,21 @@ void btrfs_put_transaction(struct btrfs_transaction *transaction)
 	}
 }
 
-static noinline void switch_commit_root(struct btrfs_root *root)
+static noinline void switch_commit_roots(struct btrfs_transaction *trans,
+					 struct btrfs_fs_info *fs_info)
 {
-	free_extent_buffer(root->commit_root);
-	root->commit_root = btrfs_root_node(root);
+	struct btrfs_root *root, *tmp;
+
+	down_write(&fs_info->commit_root_sem);
+	list_for_each_entry_safe(root, tmp, &trans->switch_commits,
+				 dirty_list) {
+		list_del_init(&root->dirty_list);
+		free_extent_buffer(root->commit_root);
+		root->commit_root = btrfs_root_node(root);
+		if (is_fstree(root->objectid))
+			btrfs_unpin_free_ino(root);
+	}
+	up_write(&fs_info->commit_root_sem);
 }
 
 static inline void extwriter_counter_inc(struct btrfs_transaction *trans,
@@ -208,6 +219,7 @@ loop:
 	INIT_LIST_HEAD(&cur_trans->pending_snapshots);
 	INIT_LIST_HEAD(&cur_trans->ordered_operations);
 	INIT_LIST_HEAD(&cur_trans->pending_chunks);
+	INIT_LIST_HEAD(&cur_trans->switch_commits);
 	list_add_tail(&cur_trans->list, &fs_info->trans_list);
 	extent_io_tree_init(&cur_trans->dirty_pages,
 			     fs_info->btree_inode->i_mapping);
@@ -920,9 +932,6 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans,
 			return ret;
 	}
 
-	if (root != root->fs_info->extent_root)
-		switch_commit_root(root);
-
 	return 0;
 }
 
@@ -978,15 +987,16 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
 		list_del_init(next);
 		root = list_entry(next, struct btrfs_root, dirty_list);
 
+		if (root != fs_info->extent_root)
+			list_add_tail(&root->dirty_list,
+				      &trans->transaction->switch_commits);
 		ret = update_cowonly_root(trans, root);
 		if (ret)
 			return ret;
 	}
 
-	down_write(&fs_info->extent_commit_sem);
-	switch_commit_root(fs_info->extent_root);
-	up_write(&fs_info->extent_commit_sem);
-
+	list_add_tail(&fs_info->extent_root->dirty_list,
+		      &trans->transaction->switch_commits);
 	btrfs_after_dev_replace_commit(fs_info);
 
 	return 0;
@@ -1043,11 +1053,8 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
 			smp_wmb();
 
 			if (root->commit_root != root->node) {
-				mutex_lock(&root->fs_commit_mutex);
-				switch_commit_root(root);
-				btrfs_unpin_free_ino(root);
-				mutex_unlock(&root->fs_commit_mutex);
-
+				list_add_tail(&root->dirty_list,
+					&trans->transaction->switch_commits);
 				btrfs_set_root_node(&root->root_item,
 						    root->node);
 			}
@@ -1858,11 +1865,15 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 
 	btrfs_set_root_node(&root->fs_info->tree_root->root_item,
 			    root->fs_info->tree_root->node);
-	switch_commit_root(root->fs_info->tree_root);
+	list_add_tail(&root->fs_info->tree_root->dirty_list,
+		      &cur_trans->switch_commits);
 
 	btrfs_set_root_node(&root->fs_info->chunk_root->root_item,
 			    root->fs_info->chunk_root->node);
-	switch_commit_root(root->fs_info->chunk_root);
+	list_add_tail(&root->fs_info->chunk_root->dirty_list,
+		      &cur_trans->switch_commits);
+
+	switch_commit_roots(cur_trans, root->fs_info);
 
 	assert_qgroups_uptodate(trans);
 	update_super_roots(root);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 2bcba89..b57b924 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -57,6 +57,7 @@ struct btrfs_transaction {
 	struct list_head pending_snapshots;
 	struct list_head ordered_operations;
 	struct list_head pending_chunks;
+	struct list_head switch_commits;
 	struct btrfs_delayed_ref_root delayed_refs;
 	int aborted;
 };