[PATCH 2/2 v3] ext4: introduce ext4_get_group_number()

[Lukas Czerner <lczerner@redhat.com>]

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>
---
v2: Update after patch 0001 changed
v3: Use test_opt2/set_opt2

 fs/ext4/balloc.c  |   25 ++++++++++++++++++-------
 fs/ext4/ext4.h    |    3 +++
 fs/ext4/mballoc.c |    6 +++---
 fs/ext4/resize.c  |   10 +++++-----
 4 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index d6babf9..1033674 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -30,6 +30,23 @@ static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
  */
 
 /*
+ * Calculate block group number for a given block number
+ */
+inline 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;
 }
 
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 87572c1..655d7ff 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1795,6 +1795,9 @@ ext4_group_first_block_no(struct super_block *sb, ext4_group_t group_no)
 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
 			ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp);
 
+inline ext4_group_t ext4_get_group_number(struct super_block *sb,
+					  ext4_fsblk_t block);
+
 /*
  * Timeout and state flag for lazy initialization inode thread.
  */
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index ee6614b..dca7f06 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3342,7 +3342,7 @@ 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:
@@ -3807,7 +3807,7 @@ repeat:
 
 	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) {
@@ -4069,7 +4069,7 @@ 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);
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index c169477..e349853 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -272,7 +272,7 @@ next_group:
 		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 @@ next_group:
 		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 @@ next_group:
 		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 @@ retry:
 		/* 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);
-- 
1.7.7.6