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>

1 files changed, 18 insertions, 7 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index d6babf9..9e8d8ff 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
+ */
+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;
 }