btrfs: tag as unlikely error conditions in the transaction commit path

Errors are unexpected during the transaction commit path, and when they
happen we abort the transaction (by calling cleanup_transaction() under
the label 'cleanup_transaction' in btrfs_commit_transaction()). So mark
every error check in the transaction commit path as unlikely, to hint the
compiler so that it can possibly generate better code, and make it clear
for a reader about being unexpected.

On a x86_84 box using gcc 14.2.0-19 from Debian, this resulted in a slight
reduction of the module's text size.

Before:

  $ size fs/btrfs/btrfs.ko
     text	   data	    bss	    dec	    hex	filename
  1939476	 172568	  15592	2127636	 207714	fs/btrfs/btrfs.ko

After:

  $ size fs/btrfs/btrfs.ko
     text	   data	    bss	    dec	    hex	filename
  1939044	 172568	  15592	2127204	 207564	fs/btrfs/btrfs.ko

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

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index d29d32dff6e3124698ecdf9195de3dced8b51809..e2f993b1783fad2b16c923669bc9e8dbd5594ae1 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1515,7 +1515,7 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
 
                        btrfs_free_log(trans, root);
                        ret2 = btrfs_update_reloc_root(trans, root);
-                       if (ret2)
+                       if (unlikely(ret2))
                                return ret2;
 
                        /* see comments in should_cow_block() */
@@ -1532,7 +1532,7 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
                        ret2 = btrfs_update_root(trans, fs_info->tree_root,
                                                &root->root_key,
                                                &root->root_item);
-                       if (ret2)
+                       if (unlikely(ret2))
                                return ret2;
                        spin_lock(&fs_info->fs_roots_radix_lock);
                }
@@ -1687,11 +1687,11 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
                                                &pending->dentry->d_name, 0,
                                                &fname);
        memalloc_nofs_restore(nofs_flags);
-       if (pending->error)
+       if (unlikely(pending->error))
                goto free_pending;
 
        pending->error = btrfs_get_free_objectid(tree_root, &objectid);
-       if (pending->error)
+       if (unlikely(pending->error))
                goto free_fname;
 
        /*
@@ -1707,7 +1707,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
                                                     &pending->block_rsv,
                                                     to_reserve,
                                                     BTRFS_RESERVE_NO_FLUSH);
-               if (pending->error)
+               if (unlikely(pending->error))
                        goto clear_skip_qgroup;
        }
 
@@ -1719,7 +1719,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
                                      trans->bytes_reserved, 1);
        parent_root = parent_inode->root;
        ret = record_root_in_trans(trans, parent_root, 0);
-       if (ret)
+       if (unlikely(ret))
                goto fail;
        cur_time = current_time(&parent_inode->vfs_inode);
 
@@ -1736,7 +1736,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
        dir_item = btrfs_lookup_dir_item(NULL, parent_root, path,
                                         btrfs_ino(parent_inode),
                                         &fname.disk_name, 0);
-       if (dir_item != NULL && !IS_ERR(dir_item)) {
+       if (unlikely(dir_item != NULL && !IS_ERR(dir_item))) {
                pending->error = -EEXIST;
                goto dir_item_existed;
        } else if (IS_ERR(dir_item)) {
@@ -1873,7 +1873,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
        else if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_SIMPLE)
                ret = btrfs_qgroup_inherit(trans, btrfs_root_id(root), objectid,
                                           btrfs_root_id(parent_root), pending->inherit);
-       if (ret < 0)
+       if (unlikely(ret < 0))
                goto fail;
 
        ret = btrfs_insert_dir_item(trans, &fname.disk_name,
@@ -1939,7 +1939,7 @@ static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans)
        list_for_each_entry_safe(pending, next, head, list) {
                list_del(&pending->list);
                ret = create_pending_snapshot(trans, pending);
-               if (ret)
+               if (unlikely(ret))
                        break;
        }
        return ret;
@@ -2258,7 +2258,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
                if (run_it) {
                        ret = btrfs_start_dirty_block_groups(trans);
-                       if (ret)
+                       if (unlikely(ret))
                                goto lockdep_trans_commit_start_release;
                }
        }
@@ -2308,7 +2308,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
                        ret = READ_ONCE(prev_trans->aborted);
 
                        btrfs_put_transaction(prev_trans);
-                       if (ret)
+                       if (unlikely(ret))
                                goto lockdep_release;
                        spin_lock(&fs_info->trans_lock);
                }
@@ -2338,11 +2338,11 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
        extwriter_counter_dec(cur_trans, trans->type);
 
        ret = btrfs_start_delalloc_flush(fs_info);
-       if (ret)
+       if (unlikely(ret))
                goto lockdep_release;
 
        ret = btrfs_run_delayed_items(trans);
-       if (ret)
+       if (unlikely(ret))
                goto lockdep_release;
 
        /*
@@ -2357,7 +2357,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
 
        /* some pending stuffs might be added after the previous flush. */
        ret = btrfs_run_delayed_items(trans);
-       if (ret) {
+       if (unlikely(ret)) {
                btrfs_lockdep_release(fs_info, btrfs_trans_num_writers);
                goto cleanup_transaction;
        }
@@ -2429,7 +2429,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
         * core function of the snapshot creation.
         */
        ret = create_pending_snapshots(trans);
-       if (ret)
+       if (unlikely(ret))
                goto unlock_reloc;
 
        /*
@@ -2443,11 +2443,11 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
         * the nodes and leaves.
         */
        ret = btrfs_run_delayed_items(trans);
-       if (ret)
+       if (unlikely(ret))
                goto unlock_reloc;
 
        ret = btrfs_run_delayed_refs(trans, U64_MAX);
-       if (ret)
+       if (unlikely(ret))
                goto unlock_reloc;
 
        /*
@@ -2459,7 +2459,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
        WARN_ON(cur_trans != trans->transaction);
 
        ret = commit_fs_roots(trans);
-       if (ret)
+       if (unlikely(ret))
                goto unlock_reloc;
 
        /* commit_fs_roots gets rid of all the tree log roots, it is now
@@ -2472,11 +2472,11 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
         * new_roots. So let's do quota accounting.
         */
        ret = btrfs_qgroup_account_extents(trans);
-       if (ret < 0)
+       if (unlikely(ret < 0))
                goto unlock_reloc;
 
        ret = commit_cowonly_roots(trans);
-       if (ret)
+       if (unlikely(ret))
                goto unlock_reloc;
 
        /*
@@ -2562,7 +2562,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
         * to go about their business
         */
        mutex_unlock(&fs_info->tree_log_mutex);
-       if (ret)
+       if (unlikely(ret))
                goto scrub_continue;
 
        update_commit_stats(fs_info);
@@ -2575,7 +2575,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans)
        btrfs_trans_state_lockdep_release(fs_info, BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED);
 
        ret = btrfs_finish_extent_commit(trans);
-       if (ret)
+       if (unlikely(ret))
                goto scrub_continue;
 
        if (test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &cur_trans->flags))