ext4: factor out block group accounting into functions

This makes it easier to understand how ext4_init_block_bitmap() works,
and it will assist when we split out ext4_free_blocks_after_init() in
the next commit.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 48 insertions, 32 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index f8224adf496e..8573e2bfb78a 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -23,6 +23,9 @@
 
 #include <trace/events/ext4.h>
 
+static unsigned int num_base_meta_blocks(struct super_block *sb,
+                                         ext4_group_t block_group);
+
 /*
  * balloc.c contains the blocks allocation and deallocation routines
  */
@@ -83,14 +86,30 @@ static int ext4_group_used_meta_blocks(struct super_block *sb,
         return used_blocks;
 }
 
+static unsigned int num_blocks_in_group(struct super_block *sb,
+                                        ext4_group_t block_group)
+{
+        if (block_group == ext4_get_groups_count(sb) - 1) {
+                /*
+                 * Even though mke2fs always initializes the first and
+                 * last group, just in case some other tool was used,
+                 * we need to make sure we calculate the right free
+                 * blocks.
+                 */
+                return ext4_blocks_count(EXT4_SB(sb)->s_es) -
+                        ext4_group_first_block_no(sb, block_group);
+        } else
+                return EXT4_BLOCKS_PER_GROUP(sb);
+}
+
 /* Initializes an uninitialized block bitmap if given, and returns the
  * number of blocks free in the group. */
 unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
                  ext4_group_t block_group, struct ext4_group_desc *gdp)
 {
-        int bit, bit_max;
+        unsigned int bit, bit_max = num_base_meta_blocks(sb, block_group);
         ext4_group_t ngroups = ext4_get_groups_count(sb);
-        unsigned free_blocks, group_blocks;
+        unsigned group_blocks = num_blocks_in_group(sb, block_group);
         struct ext4_sb_info *sbi = EXT4_SB(sb);
 
         if (bh) {
@@ -110,35 +129,6 @@ unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
                 memset(bh->b_data, 0, sb->s_blocksize);
         }
 
-        /* Check for superblock and gdt backups in this group */
-        bit_max = ext4_bg_has_super(sb, block_group);
-
-        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
-            block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
-                          sbi->s_desc_per_block) {
-                if (bit_max) {
-                        bit_max += ext4_bg_num_gdb(sb, block_group);
-                        bit_max +=
-                                le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
-                }
-        } else { /* For META_BG_BLOCK_GROUPS */
-                bit_max += ext4_bg_num_gdb(sb, block_group);
-        }
-
-        if (block_group == ngroups - 1) {
-                /*
-                 * Even though mke2fs always initialize first and last group
-                 * if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
-                 * to make sure we calculate the right free blocks
-                 */
-                group_blocks = ext4_blocks_count(sbi->s_es) -
-                        ext4_group_first_block_no(sb, ngroups - 1);
-        } else {
-                group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
-        }
-
-        free_blocks = group_blocks - bit_max;
-
         if (bh) {
                 ext4_fsblk_t start, tmp;
                 int flex_bg = 0;
@@ -176,7 +166,8 @@ unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
                 ext4_mark_bitmap_end(group_blocks, sb->s_blocksize * 8,
                                      bh->b_data);
         }
-        return free_blocks - ext4_group_used_meta_blocks(sb, block_group, gdp);
+        return group_blocks - bit_max -
+                ext4_group_used_meta_blocks(sb, block_group, gdp);
 }
 
 
@@ -620,6 +611,31 @@ unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 
 }
 
+/*
+ * This function returns the number of file system metadata blocks at
+ * the beginning of a block group, including the reserved gdt blocks.
+ */
+static unsigned int num_base_meta_blocks(struct super_block *sb,
+                                         ext4_group_t block_group)
+{
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
+        int num;
+
+        /* Check for superblock and gdt backups in this group */
+        num = ext4_bg_has_super(sb, block_group);
+
+        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
+            block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
+                          sbi->s_desc_per_block) {
+                if (num) {
+                        num += ext4_bg_num_gdb(sb, block_group);
+                        num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
+                }
+        } else { /* For META_BG_BLOCK_GROUPS */
+                num += ext4_bg_num_gdb(sb, block_group);
+        }
+        return num;
+}
 /**
  *      ext4_inode_to_goal_block - return a hint for block allocation
  *      @inode: inode for block allocation