ext4: split out ext4_free_blocks_after_init()

The function ext4_free_blocks_after_init() used to be a #define of
ext4_init_block_bitmap().  This actually made it difficult to
understand how the function worked, and made it hard make changes to
support clusters.  So as an initial cleanup, I've separated out the
functionality of initializing block bitmap from calculating the number
of free blocks in the new block group.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/balloc.c

@@ -102,74 +102,73 @@ static unsigned int num_blocks_in_group(struct super_block *sb,
 		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)
+/* Initializes an uninitialized block bitmap */
+void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
+			    ext4_group_t block_group,
+			    struct ext4_group_desc *gdp)
 {
 	unsigned int bit, bit_max = num_base_meta_blocks(sb, block_group);
-	ext4_group_t ngroups = ext4_get_groups_count(sb);
-	unsigned group_blocks = num_blocks_in_group(sb, block_group);
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-
-	if (bh) {
-		J_ASSERT_BH(bh, buffer_locked(bh));
-
-		/* If checksum is bad mark all blocks used to prevent allocation
-		 * essentially implementing a per-group read-only flag. */
-		if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
-			ext4_error(sb, "Checksum bad for group %u",
-					block_group);
-			ext4_free_blks_set(sb, gdp, 0);
-			ext4_free_inodes_set(sb, gdp, 0);
-			ext4_itable_unused_set(sb, gdp, 0);
-			memset(bh->b_data, 0xff, sb->s_blocksize);
-			return 0;
-		}
-		memset(bh->b_data, 0, sb->s_blocksize);
+	ext4_fsblk_t start, tmp;
+	int flex_bg = 0;
+
+	J_ASSERT_BH(bh, buffer_locked(bh));
+
+	/* If checksum is bad mark all blocks used to prevent allocation
+	 * essentially implementing a per-group read-only flag. */
+	if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
+		ext4_error(sb, "Checksum bad for group %u", block_group);
+		ext4_free_blks_set(sb, gdp, 0);
+		ext4_free_inodes_set(sb, gdp, 0);
+		ext4_itable_unused_set(sb, gdp, 0);
+		memset(bh->b_data, 0xff, sb->s_blocksize);
+		return;
 	}
+	memset(bh->b_data, 0, sb->s_blocksize);
 
-	if (bh) {
-		ext4_fsblk_t start, tmp;
-		int flex_bg = 0;
+	for (bit = 0; bit < bit_max; bit++)
+		ext4_set_bit(bit, bh->b_data);
 
-		for (bit = 0; bit < bit_max; bit++)
-			ext4_set_bit(bit, bh->b_data);
+	start = ext4_group_first_block_no(sb, block_group);
 
-		start = ext4_group_first_block_no(sb, block_group);
+	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
+		flex_bg = 1;
 
-		if (EXT4_HAS_INCOMPAT_FEATURE(sb,
-					      EXT4_FEATURE_INCOMPAT_FLEX_BG))
-			flex_bg = 1;
+	/* Set bits for block and inode bitmaps, and inode table */
+	tmp = ext4_block_bitmap(sb, gdp);
+	if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
+		ext4_set_bit(tmp - start, bh->b_data);
 
-		/* Set bits for block and inode bitmaps, and inode table */
-		tmp = ext4_block_bitmap(sb, gdp);
-		if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
-			ext4_set_bit(tmp - start, bh->b_data);
+	tmp = ext4_inode_bitmap(sb, gdp);
+	if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
+		ext4_set_bit(tmp - start, bh->b_data);
 
-		tmp = ext4_inode_bitmap(sb, gdp);
+	tmp = ext4_inode_table(sb, gdp);
+	for (; tmp < ext4_inode_table(sb, gdp) +
+		     sbi->s_itb_per_group; tmp++) {
 		if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 			ext4_set_bit(tmp - start, bh->b_data);
-
-		tmp = ext4_inode_table(sb, gdp);
-		for (; tmp < ext4_inode_table(sb, gdp) +
-				sbi->s_itb_per_group; tmp++) {
-			if (!flex_bg ||
-				ext4_block_in_group(sb, tmp, block_group))
-				ext4_set_bit(tmp - start, bh->b_data);
-		}
-		/*
-		 * Also if the number of blocks within the group is
-		 * less than the blocksize * 8 ( which is the size
-		 * of bitmap ), set rest of the block bitmap to 1
-		 */
-		ext4_mark_bitmap_end(group_blocks, sb->s_blocksize * 8,
-				     bh->b_data);
 	}
-	return group_blocks - bit_max -
-		ext4_group_used_meta_blocks(sb, block_group, gdp);
+	/*
+	 * Also if the number of blocks within the group is less than
+	 * the blocksize * 8 ( which is the size of bitmap ), set rest
+	 * of the block bitmap to 1
+	 */
+	ext4_mark_bitmap_end(num_blocks_in_group(sb, block_group),
+			     sb->s_blocksize * 8, bh->b_data);
 }
 
+/* Return the number of free blocks in a block group.  It is used when
+ * the block bitmap is uninitialized, so we can't just count the bits
+ * in the bitmap. */
+unsigned ext4_free_blocks_after_init(struct super_block *sb,
+				     ext4_group_t block_group,
+				     struct ext4_group_desc *gdp)
+{
+	return num_blocks_in_group(sb, block_group) -
+		num_base_meta_blocks(sb, block_group) -
+		ext4_group_used_meta_blocks(sb, block_group, gdp);
+}
 
 /*
  * The free blocks are managed by bitmaps.  A file system contains several

fs/ext4/ext4.h

@@ -1763,12 +1763,13 @@ extern struct ext4_group_desc * ext4_get_group_desc(struct super_block * sb,
 extern int ext4_should_retry_alloc(struct super_block *sb, int *retries);
 struct buffer_head *ext4_read_block_bitmap(struct super_block *sb,
 				      ext4_group_t block_group);
-extern unsigned ext4_init_block_bitmap(struct super_block *sb,
-				       struct buffer_head *bh,
-				       ext4_group_t group,
-				       struct ext4_group_desc *desc);
-#define ext4_free_blocks_after_init(sb, group, desc)			\
-		ext4_init_block_bitmap(sb, NULL, group, desc)
+extern void ext4_init_block_bitmap(struct super_block *sb,
+				   struct buffer_head *bh,
+				   ext4_group_t group,
+				   struct ext4_group_desc *desc);
+extern unsigned ext4_free_blocks_after_init(struct super_block *sb,
+					    ext4_group_t block_group,
+					    struct ext4_group_desc *gdp);
 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
 
 /* dir.c */

fs/ext4/ialloc.c

@@ -816,7 +816,6 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
 	int ret2, err = 0;
 	struct inode *ret;
 	ext4_group_t i;
-	int free = 0;
 	static int once = 1;
 	ext4_group_t flex_group;
 
@@ -950,26 +949,21 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
 			goto fail;
 		}
 
-		free = 0;
-		ext4_lock_group(sb, group);
+		BUFFER_TRACE(block_bitmap_bh, "dirty block bitmap");
+		err = ext4_handle_dirty_metadata(handle, NULL, block_bitmap_bh);
+		brelse(block_bitmap_bh);
+
 		/* recheck and clear flag under lock if we still need to */
+		ext4_lock_group(sb, group);
 		if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
-			free = ext4_free_blocks_after_init(sb, group, gdp);
 			gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
-			ext4_free_blks_set(sb, gdp, free);
+			ext4_free_blks_set(sb, gdp,
+				ext4_free_blocks_after_init(sb, group, gdp));
 			gdp->bg_checksum = ext4_group_desc_csum(sbi, group,
 								gdp);
 		}
 		ext4_unlock_group(sb, group);
 
-		/* Don't need to dirty bitmap block if we didn't change it */
-		if (free) {
-			BUFFER_TRACE(block_bitmap_bh, "dirty block bitmap");
-			err = ext4_handle_dirty_metadata(handle,
-							NULL, block_bitmap_bh);
-		}
-
-		brelse(block_bitmap_bh);
 		if (err)
 			goto fail;
 	}