ext4: cleanup to use ext4_grp_offs_to_block()

More cleanup to convert open-coded calculations of the first block
number of a free extent to use ext4_grp_offs_to_block() instead.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger@sun.com>

fs/ext4/mballoc.c

@@ -2697,9 +2697,7 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
 	if (err)
 		goto out_err;
 
-	block = ac->ac_b_ex.fe_group * EXT4_BLOCKS_PER_GROUP(sb)
-		+ ac->ac_b_ex.fe_start
-		+ le32_to_cpu(es->s_first_data_block);
+	block = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
 
 	len = ac->ac_b_ex.fe_len;
 	if (!ext4_data_block_valid(sbi, block, len)) {
@@ -3154,9 +3152,7 @@ ext4_mb_use_preallocated(struct ext4_allocation_context *ac)
 		/* The max size of hash table is PREALLOC_TB_SIZE */
 		order = PREALLOC_TB_SIZE - 1;
 
-	goal_block = ac->ac_g_ex.fe_group * EXT4_BLOCKS_PER_GROUP(ac->ac_sb) +
-		     ac->ac_g_ex.fe_start +
-		     le32_to_cpu(EXT4_SB(ac->ac_sb)->s_es->s_first_data_block);
+	goal_block = ext4_grp_offs_to_block(ac->ac_sb, &ac->ac_g_ex);
 	/*
 	 * search for the prealloc space that is having
 	 * minimal distance from the goal block.