ext4: remove unnecessary goto in ext4_mb_mark_diskspace_used

When ext4_read_block_bitmap fails, we can return PTR_ERR(bitmap_bh) to
remove unnecessary NULL check of bitmap_bh.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20230303172120.3800725-18-shikemeng@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -3739,9 +3739,7 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
 
 	bitmap_bh = ext4_read_block_bitmap(sb, ac->ac_b_ex.fe_group);
 	if (IS_ERR(bitmap_bh)) {
-		err = PTR_ERR(bitmap_bh);
-		bitmap_bh = NULL;
-		goto out_err;
+		return PTR_ERR(bitmap_bh);
 	}
 
 	BUFFER_TRACE(bitmap_bh, "getting write access");