ext4: bigalloc changes to block bitmap initialization functions

Add bigalloc support to ext4_init_block_bitmap() and
ext4_free_blocks_after_init().
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/balloc.c

@@ -23,9 +23,6 @@
 
 #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
  */
@@ -58,37 +55,87 @@ static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
 	return 0;
 }
 
-static int ext4_group_used_meta_blocks(struct super_block *sb,
-				       ext4_group_t block_group,
-				       struct ext4_group_desc *gdp)
+/* Return the number of clusters used for file system metadata; this
+ * represents the overhead needed by the file system.
+ */
+unsigned ext4_num_overhead_clusters(struct super_block *sb,
+				    ext4_group_t block_group,
+				    struct ext4_group_desc *gdp)
 {
-	ext4_fsblk_t tmp;
+	unsigned num_clusters;
+	int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
+	ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
+	ext4_fsblk_t itbl_blk;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	/* block bitmap, inode bitmap, and inode table blocks */
-	int used_blocks = sbi->s_itb_per_group + 2;
 
-	if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
-		if (!ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp),
-					block_group))
-			used_blocks--;
-
-		if (!ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp),
-					block_group))
-			used_blocks--;
-
-		tmp = ext4_inode_table(sb, gdp);
-		for (; tmp < ext4_inode_table(sb, gdp) +
-				sbi->s_itb_per_group; tmp++) {
-			if (!ext4_block_in_group(sb, tmp, block_group))
-				used_blocks -= 1;
+	/* This is the number of clusters used by the superblock,
+	 * block group descriptors, and reserved block group
+	 * descriptor blocks */
+	num_clusters = ext4_num_base_meta_clusters(sb, block_group);
+
+	/*
+	 * For the allocation bitmaps and inode table, we first need
+	 * to check to see if the block is in the block group.  If it
+	 * is, then check to see if the cluster is already accounted
+	 * for in the clusters used for the base metadata cluster, or
+	 * if we can increment the base metadata cluster to include
+	 * that block.  Otherwise, we will have to track the cluster
+	 * used for the allocation bitmap or inode table explicitly.
+	 * Normally all of these blocks are contiguous, so the special
+	 * case handling shouldn't be necessary except for *very*
+	 * unusual file system layouts.
+	 */
+	if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
+		block_cluster = EXT4_B2C(sbi, (start -
+					       ext4_block_bitmap(sb, gdp)));
+		if (block_cluster < num_clusters)
+			block_cluster = -1;
+		else if (block_cluster == num_clusters) {
+			num_clusters++;
+			block_cluster = -1;
+		}
+	}
+
+	if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
+		inode_cluster = EXT4_B2C(sbi,
+					 start - ext4_inode_bitmap(sb, gdp));
+		if (inode_cluster < num_clusters)
+			inode_cluster = -1;
+		else if (inode_cluster == num_clusters) {
+			num_clusters++;
+			inode_cluster = -1;
+		}
+	}
+
+	itbl_blk = ext4_inode_table(sb, gdp);
+	for (i = 0; i < sbi->s_itb_per_group; i++) {
+		if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {
+			c = EXT4_B2C(sbi, start - itbl_blk + i);
+			if ((c < num_clusters) || (c == inode_cluster) ||
+			    (c == block_cluster) || (c == itbl_cluster))
+				continue;
+			if (c == num_clusters) {
+				num_clusters++;
+				continue;
+			}
+			num_clusters++;
+			itbl_cluster = c;
 		}
 	}
-	return used_blocks;
+
+	if (block_cluster != -1)
+		num_clusters++;
+	if (inode_cluster != -1)
+		num_clusters++;
+
+	return num_clusters;
 }
 
-static unsigned int num_blocks_in_group(struct super_block *sb,
-					ext4_group_t block_group)
+static unsigned int num_clusters_in_group(struct super_block *sb,
+					  ext4_group_t block_group)
 {
+	unsigned int blocks;
+
 	if (block_group == ext4_get_groups_count(sb) - 1) {
 		/*
 		 * Even though mke2fs always initializes the first and
@@ -96,10 +143,11 @@ static unsigned int num_blocks_in_group(struct super_block *sb,
 		 * we need to make sure we calculate the right free
 		 * blocks.
 		 */
-		return ext4_blocks_count(EXT4_SB(sb)->s_es) -
+		blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) -
 			ext4_group_first_block_no(sb, block_group);
 	} else
-		return EXT4_BLOCKS_PER_GROUP(sb);
+		blocks = EXT4_BLOCKS_PER_GROUP(sb);
+	return EXT4_NUM_B2C(EXT4_SB(sb), blocks);
 }
 
 /* Initializes an uninitialized block bitmap */
@@ -107,7 +155,7 @@ 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);
+	unsigned int bit, bit_max;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	ext4_fsblk_t start, tmp;
 	int flex_bg = 0;
@@ -126,6 +174,7 @@ void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
 	}
 	memset(bh->b_data, 0, sb->s_blocksize);
 
+	bit_max = ext4_num_base_meta_clusters(sb, block_group);
 	for (bit = 0; bit < bit_max; bit++)
 		ext4_set_bit(bit, bh->b_data);
 
@@ -137,24 +186,25 @@ void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
 	/* 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);
+		ext4_set_bit(EXT4_B2C(sbi, 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);
+		ext4_set_bit(EXT4_B2C(sbi, 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);
+			ext4_set_bit(EXT4_B2C(sbi, 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(num_blocks_in_group(sb, block_group),
+	ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
 			     sb->s_blocksize * 8, bh->b_data);
 }
 
@@ -165,9 +215,8 @@ 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);
+	return num_clusters_in_group(sb, block_group) - 
+		ext4_num_overhead_clusters(sb, block_group, gdp);
 }
 
 /*
@@ -611,14 +660,14 @@ 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
+ * This function returns the number of file system metadata clusters 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)
+unsigned ext4_num_base_meta_clusters(struct super_block *sb,
+				     ext4_group_t block_group)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	int num;
+	unsigned num;
 
 	/* Check for superblock and gdt backups in this group */
 	num = ext4_bg_has_super(sb, block_group);
@@ -633,7 +682,7 @@ static unsigned int num_base_meta_blocks(struct super_block *sb,
 	} else { /* For META_BG_BLOCK_GROUPS */
 		num += ext4_bg_num_gdb(sb, block_group);
 	}
-	return num;
+	return EXT4_NUM_B2C(sbi, num);
 }
 /**
  *	ext4_inode_to_goal_block - return a hint for block allocation

fs/ext4/ext4.h

@@ -261,6 +261,14 @@ struct ext4_io_submit {
 #endif
 #define EXT4_BLOCK_ALIGN(size, blkbits)		ALIGN((size), (1 << (blkbits)))
 
+/* Translate a block number to a cluster number */
+#define EXT4_B2C(sbi, blk)	((blk) >> (sbi)->s_cluster_bits)
+/* Translate a cluster number to a block number */
+#define EXT4_C2B(sbi, cluster)	((cluster) << (sbi)->s_cluster_bits)
+/* Translate # of blks to # of clusters */
+#define EXT4_NUM_B2C(sbi, blks)	(((blks) + (sbi)->s_cluster_ratio - 1) >> \
+				 (sbi)->s_cluster_bits)
+
 /*
  * Structure of a blocks group descriptor
  */
@@ -1770,6 +1778,11 @@ extern void ext4_init_block_bitmap(struct super_block *sb,
 extern unsigned ext4_free_blocks_after_init(struct super_block *sb,
 					    ext4_group_t block_group,
 					    struct ext4_group_desc *gdp);
+extern unsigned ext4_num_base_meta_clusters(struct super_block *sb,
+					    ext4_group_t block_group);
+extern unsigned ext4_num_overhead_clusters(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 */