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, 19 insertions, 19 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 6a258bd8693e..dc4ca98c3780 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2157,7 +2157,7 @@ again:
 	delayed_refs->run_delayed_start = find_middle(&delayed_refs->root);
 #endif
 	ret = __btrfs_run_delayed_refs(trans, min_bytes);
-	if (ret < 0) {
+	if (unlikely(ret < 0)) {
 		btrfs_abort_transaction(trans, ret);
 		return ret;
 	}
@@ -2982,26 +2982,26 @@ static int do_free_extent_accounting(struct btrfs_trans_handle *trans,
 
 		csum_root = btrfs_csum_root(trans->fs_info, bytenr);
 		ret = btrfs_del_csums(trans, csum_root, bytenr, num_bytes);
-		if (ret) {
+		if (unlikely(ret)) {
 			btrfs_abort_transaction(trans, ret);
 			return ret;
 		}
 
 		ret = btrfs_delete_raid_extent(trans, bytenr, num_bytes);
-		if (ret) {
+		if (unlikely(ret)) {
 			btrfs_abort_transaction(trans, ret);
 			return ret;
 		}
 	}
 
 	ret = btrfs_record_squota_delta(trans->fs_info, delta);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		return ret;
 	}
 
 	ret = btrfs_add_to_free_space_tree(trans, bytenr, num_bytes);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		return ret;
 	}
@@ -3115,7 +3115,7 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
 
 	is_data = owner_objectid >= BTRFS_FIRST_FREE_OBJECTID;
 
-	if (!is_data && refs_to_drop != 1) {
+	if (unlikely(!is_data && refs_to_drop != 1)) {
 		btrfs_crit(info,
 "invalid refs_to_drop, dropping more than 1 refs for tree block %llu refs_to_drop %u",
 			   node->bytenr, refs_to_drop);
@@ -3172,7 +3172,7 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
 			/* Must be SHARED_* item, remove the backref first */
 			ret = remove_extent_backref(trans, extent_root, path,
 						    NULL, refs_to_drop, is_data);
-			if (ret) {
+			if (unlikely(ret)) {
 				btrfs_abort_transaction(trans, ret);
 				goto out;
 			}
@@ -3221,7 +3221,7 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
 			"umm, got %d back from search, was looking for %llu, slot %d",
 					  ret, bytenr, path->slots[0]);
 			}
-			if (ret < 0) {
+			if (unlikely(ret < 0)) {
 				btrfs_abort_transaction(trans, ret);
 				goto out;
 			}
@@ -3298,7 +3298,7 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
 		if (found_extent) {
 			ret = remove_extent_backref(trans, extent_root, path,
 						    iref, refs_to_drop, is_data);
-			if (ret) {
+			if (unlikely(ret)) {
 				btrfs_abort_transaction(trans, ret);
 				goto out;
 			}
@@ -3363,7 +3363,7 @@ static int __btrfs_free_extent(struct btrfs_trans_handle *trans,
 
 		ret = btrfs_del_items(trans, extent_root, path, path->slots[0],
 				      num_to_del);
-		if (ret) {
+		if (unlikely(ret)) {
 			btrfs_abort_transaction(trans, ret);
 			goto out;
 		}
@@ -5472,17 +5472,17 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
 	if (!(wc->flags[level] & flag)) {
 		ASSERT(path->locks[level]);
 		ret = btrfs_inc_ref(trans, root, eb, 1);
-		if (ret) {
+		if (unlikely(ret)) {
 			btrfs_abort_transaction(trans, ret);
 			return ret;
 		}
 		ret = btrfs_dec_ref(trans, root, eb, 0);
-		if (ret) {
+		if (unlikely(ret)) {
 			btrfs_abort_transaction(trans, ret);
 			return ret;
 		}
 		ret = btrfs_set_disk_extent_flags(trans, eb, flag);
-		if (ret) {
+		if (unlikely(ret)) {
 			btrfs_abort_transaction(trans, ret);
 			return ret;
 		}
@@ -5885,7 +5885,7 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
 				}
 			} else {
 				ret = btrfs_dec_ref(trans, root, eb, 0);
-				if (ret) {
+				if (unlikely(ret)) {
 					btrfs_abort_transaction(trans, ret);
 					return ret;
 				}
@@ -6180,13 +6180,13 @@ int btrfs_drop_snapshot(struct btrfs_root *root, bool update_ref, bool for_reloc
 	while (1) {
 
 		ret = walk_down_tree(trans, root, path, wc);
-		if (ret < 0) {
+		if (unlikely(ret < 0)) {
 			btrfs_abort_transaction(trans, ret);
 			break;
 		}
 
 		ret = walk_up_tree(trans, root, path, wc, BTRFS_MAX_LEVEL);
-		if (ret < 0) {
+		if (unlikely(ret < 0)) {
 			btrfs_abort_transaction(trans, ret);
 			break;
 		}
@@ -6213,7 +6213,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root, bool update_ref, bool for_reloc
 			ret = btrfs_update_root(trans, tree_root,
 						&root->root_key,
 						root_item);
-			if (ret) {
+			if (unlikely(ret)) {
 				btrfs_abort_transaction(trans, ret);
 				goto out_end_trans;
 			}
@@ -6249,7 +6249,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root, bool update_ref, bool for_reloc
 		goto out_end_trans;
 
 	ret = btrfs_del_root(trans, &root->root_key);
-	if (ret) {
+	if (unlikely(ret)) {
 		btrfs_abort_transaction(trans, ret);
 		goto out_end_trans;
 	}
@@ -6257,7 +6257,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root, bool update_ref, bool for_reloc
 	if (!is_reloc_root) {
 		ret = btrfs_find_root(tree_root, &root->root_key, path,
 				      NULL, NULL);
-		if (ret < 0) {
+		if (unlikely(ret < 0)) {
 			btrfs_abort_transaction(trans, ret);
 			goto out_end_trans;
 		} else if (ret > 0) {