ext4: introduce ext4_get_group_number()

Currently on many places in ext4 we're using
ext4_get_group_no_and_offset() even though we're only interested in
knowing the block group of the particular block, not the offset within
the block group so we can use more efficient way to compute block
group.

This patch introduces ext4_get_group_number() which computes block
group for a given block much more efficiently. Use this function
instead of ext4_get_group_no_and_offset() everywhere where we're only
interested in knowing the block group.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/balloc.c

@@ -29,6 +29,23 @@ static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
  * balloc.c contains the blocks allocation and deallocation routines
  */
 
+/*
+ * Calculate block group number for a given block number
+ */
+ext4_group_t ext4_get_group_number(struct super_block *sb,
+				   ext4_fsblk_t block)
+{
+	ext4_group_t group;
+
+	if (test_opt2(sb, STD_GROUP_SIZE))
+		group = (le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block) +
+			 block) >>
+			(EXT4_BLOCK_SIZE_BITS(sb) + EXT4_CLUSTER_BITS(sb) + 3);
+	else
+		ext4_get_group_no_and_offset(sb, block, &group, NULL);
+	return group;
+}
+
 /*
  * Calculate the block group number and offset into the block/cluster
  * allocation bitmap, given a block number
@@ -59,13 +76,7 @@ static inline int ext4_block_in_group(struct super_block *sb,
 {
 	ext4_group_t actual_group;
 
-	if (test_opt2(sb, STD_GROUP_SIZE))
-		actual_group =
-			(le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block) +
-			block) >>
-			(EXT4_BLOCK_SIZE_BITS(sb) + EXT4_CLUSTER_BITS(sb) + 3);
-	else
-		ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
+	actual_group = ext4_get_group_number(sb, block);
 	return (actual_group == block_group) ? 1 : 0;
 }
 

fs/ext4/ext4.h

@@ -1793,9 +1793,6 @@ ext4_group_first_block_no(struct super_block *sb, ext4_group_t group_no)
  */
 #define ERR_BAD_DX_DIR	-75000
 
-void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
-			ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp);
-
 /*
  * Timeout and state flag for lazy initialization inode thread.
  */
@@ -1917,6 +1914,13 @@ int ext4_block_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
 				  struct buffer_head *bh);
 
 /* balloc.c */
+extern void ext4_get_group_no_and_offset(struct super_block *sb,
+					 ext4_fsblk_t blocknr,
+					 ext4_group_t *blockgrpp,
+					 ext4_grpblk_t *offsetp);
+extern ext4_group_t ext4_get_group_number(struct super_block *sb,
+					  ext4_fsblk_t block);
+
 extern void ext4_validate_block_bitmap(struct super_block *sb,
 				       struct ext4_group_desc *desc,
 				       unsigned int block_group,

fs/ext4/mballoc.c

@@ -3344,7 +3344,7 @@ static void ext4_mb_put_pa(struct ext4_allocation_context *ac,
 	if (pa->pa_type == MB_GROUP_PA)
 		grp_blk--;
 
-	ext4_get_group_no_and_offset(sb, grp_blk, &grp, NULL);
+	grp = ext4_get_group_number(sb, grp_blk);
 
 	/*
 	 * possible race:
@@ -3809,7 +3809,7 @@ void ext4_discard_preallocations(struct inode *inode)
 
 	list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {
 		BUG_ON(pa->pa_type != MB_INODE_PA);
-		ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL);
+		group = ext4_get_group_number(sb, pa->pa_pstart);
 
 		err = ext4_mb_load_buddy(sb, group, &e4b);
 		if (err) {
@@ -4071,7 +4071,7 @@ ext4_mb_discard_lg_preallocations(struct super_block *sb,
 
 	list_for_each_entry_safe(pa, tmp, &discard_list, u.pa_tmp_list) {
 
-		ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, NULL);
+		group = ext4_get_group_number(sb, pa->pa_pstart);
 		if (ext4_mb_load_buddy(sb, group, &e4b)) {
 			ext4_error(sb, "Error loading buddy information for %u",
 					group);

fs/ext4/resize.c

@@ -272,7 +272,7 @@ static int ext4_alloc_group_tables(struct super_block *sb,
 		if (start_blk >= last_blk)
 			goto next_group;
 		group_data[bb_index].block_bitmap = start_blk++;
-		ext4_get_group_no_and_offset(sb, start_blk - 1, &group, NULL);
+		group = ext4_get_group_number(sb, start_blk - 1);
 		group -= group_data[0].group;
 		group_data[group].free_blocks_count--;
 		if (flexbg_size > 1)
@@ -284,7 +284,7 @@ static int ext4_alloc_group_tables(struct super_block *sb,
 		if (start_blk >= last_blk)
 			goto next_group;
 		group_data[ib_index].inode_bitmap = start_blk++;
-		ext4_get_group_no_and_offset(sb, start_blk - 1, &group, NULL);
+		group = ext4_get_group_number(sb, start_blk - 1);
 		group -= group_data[0].group;
 		group_data[group].free_blocks_count--;
 		if (flexbg_size > 1)
@@ -296,7 +296,7 @@ static int ext4_alloc_group_tables(struct super_block *sb,
 		if (start_blk + EXT4_SB(sb)->s_itb_per_group > last_blk)
 			goto next_group;
 		group_data[it_index].inode_table = start_blk;
-		ext4_get_group_no_and_offset(sb, start_blk, &group, NULL);
+		group = ext4_get_group_number(sb, start_blk - 1);
 		group -= group_data[0].group;
 		group_data[group].free_blocks_count -=
 					EXT4_SB(sb)->s_itb_per_group;
@@ -392,7 +392,7 @@ static int set_flexbg_block_bitmap(struct super_block *sb, handle_t *handle,
 		ext4_group_t group;
 		int err;
 
-		ext4_get_group_no_and_offset(sb, block, &group, NULL);
+		group = ext4_get_group_number(sb, block);
 		start = ext4_group_first_block_no(sb, group);
 		group -= flex_gd->groups[0].group;
 
@@ -1879,7 +1879,7 @@ int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count)
 		/* Nothing need to do */
 		return 0;
 
-	ext4_get_group_no_and_offset(sb, n_blocks_count - 1, &n_group, &offset);
+	n_group = ext4_get_group_number(sb, n_blocks_count - 1);
 	ext4_get_group_no_and_offset(sb, o_blocks_count - 1, &o_group, &offset);
 
 	n_desc_blocks = num_desc_blocks(sb, n_group + 1);