btrfs: add unlikely annotations to branches leading to transaction abort

The unlikely() annotation is a static prediction hint that compiler may
use to reorder code out of hot path. We use it elsewhere (namely
tree-checker.c) for error branches that almost never happen.

Transaction abort is one such error, the btrfs_abort_transaction()
inlines code to check the state and print a warning, this ought to be
out of the hot path.

The most common pattern is when transaction abort is called after
checking a return value and the control flow leads to a quick return.
In other cases it may not be necessary to add unlikely() e.g. when the
function returns anyway or the control flow is not changed noticeably.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 14 insertions, 14 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 12558404f927..23bcd3c0fc1c 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1569,7 +1569,7 @@ static int qgroup_account_snapshot(struct btrfs_trans_handle *trans,
 	 * qgroup counters could end up wrong.
 	 */
 	ret = btrfs_run_delayed_refs(trans, U64_MAX);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		return ret;
 	}
@@ -1710,7 +1710,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	 * insert the directory item
 	 */
 	ret = btrfs_set_inode_index(parent_inode, &index);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1731,7 +1731,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 
 	ret = btrfs_create_qgroup(trans, objectid);
 	if (ret && ret != -EEXIST) {
-		if (ret != -ENOTCONN || btrfs_qgroup_enabled(fs_info)) {
+		if (unlikely(ret != -ENOTCONN || btrfs_qgroup_enabled(fs_info))) {
 			btrfs_abort_transaction(trans, ret);
 			goto fail;
 		}
@@ -1744,13 +1744,13 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	 * snapshot
 	 */
 	ret = btrfs_run_delayed_items(trans);
-	if (ret) {	/* Transaction aborted */
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
 
 	ret = record_root_in_trans(trans, root, 0);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1785,7 +1785,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	old = btrfs_lock_root_node(root);
 	ret = btrfs_cow_block(trans, root, old, NULL, 0, &old,
 			      BTRFS_NESTING_COW);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_tree_unlock(old);
 		free_extent_buffer(old);
 		btrfs_abort_transaction(trans, ret);
@@ -1796,7 +1796,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	/* clean up in any case */
 	btrfs_tree_unlock(old);
 	free_extent_buffer(old);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1812,7 +1812,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	ret = btrfs_insert_root(trans, tree_root, &key, new_root_item);
 	btrfs_tree_unlock(tmp);
 	free_extent_buffer(tmp);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1824,7 +1824,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 				 btrfs_root_id(parent_root),
 				 btrfs_ino(parent_inode), index,
 				 &fname.disk_name);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1839,7 +1839,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	}
 
 	ret = btrfs_reloc_post_snapshot(trans, pending);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1862,7 +1862,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	ret = btrfs_insert_dir_item(trans, &fname.disk_name,
 				    parent_inode, &key, BTRFS_FT_DIR,
 				    index);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1872,14 +1872,14 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 	inode_set_mtime_to_ts(&parent_inode->vfs_inode,
 			      inode_set_ctime_current(&parent_inode->vfs_inode));
 	ret = btrfs_update_inode_fallback(trans, parent_inode);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
 	ret = btrfs_uuid_tree_add(trans, new_root_item->uuid,
 				  BTRFS_UUID_KEY_SUBVOL,
 				  objectid);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto fail;
 	}
@@ -1887,7 +1887,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
 		ret = btrfs_uuid_tree_add(trans, new_root_item->received_uuid,
 					  BTRFS_UUID_KEY_RECEIVED_SUBVOL,
 					  objectid);
-		if (ret && ret != -EEXIST) {
+		if (unlikely(ret && ret != -EEXIST)) {
 			btrfs_abort_transaction(trans, ret);
 			goto fail;
 		}