ext4: add support for online resizing with bigalloc

This patch adds support for online resizing on bigalloc file system by
implementing EXT4_IOC_RESIZE_FS ioctl. Old resize interfaces (add
block groups and extend last block group) are left untouched. Tests
performed with cluster sizes of 1, 2, 4 and 8 blocks (of size 4k) per
cluster. I will add these tests to xfstests.
Signed-off-by: Harshad Shirwadkar <harshads@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -545,8 +545,8 @@ struct ext4_new_group_data {
 	__u64 inode_table;
 	__u32 blocks_count;
 	__u16 reserved_blocks;
-	__u16 unused;
-	__u32 free_blocks_count;
+	__u16 mdata_blocks;
+	__u32 free_clusters_count;
 };
 
 /* Indexes used to index group tables in ext4_new_group_data */

fs/ext4/ioctl.c

@@ -871,12 +871,6 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		int err = 0, err2 = 0;
 		ext4_group_t o_group = EXT4_SB(sb)->s_groups_count;
 
-		if (ext4_has_feature_bigalloc(sb)) {
-			ext4_msg(sb, KERN_ERR,
-				 "Online resizing not (yet) supported with bigalloc");
-			return -EOPNOTSUPP;
-		}
-
 		if (copy_from_user(&n_blocks_count, (__u64 __user *)arg,
 				   sizeof(__u64))) {
 			return -EFAULT;

fs/ext4/mballoc.c

@@ -4994,8 +4994,11 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
 	struct ext4_group_desc *desc;
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_buddy e4b;
-	int err = 0, ret, blk_free_count;
-	ext4_grpblk_t blocks_freed;
+	int err = 0, ret, free_clusters_count;
+	ext4_grpblk_t clusters_freed;
+	ext4_fsblk_t first_cluster = EXT4_B2C(sbi, block);
+	ext4_fsblk_t last_cluster = EXT4_B2C(sbi, block + count - 1);
+	unsigned long cluster_count = last_cluster - first_cluster + 1;
 
 	ext4_debug("Adding block(s) %llu-%llu\n", block, block + count - 1);
 
@@ -5007,8 +5010,8 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
 	 * Check to see if we are freeing blocks across a group
 	 * boundary.
 	 */
-	if (bit + count > EXT4_BLOCKS_PER_GROUP(sb)) {
-		ext4_warning(sb, "too much blocks added to group %u",
+	if (bit + cluster_count > EXT4_CLUSTERS_PER_GROUP(sb)) {
+		ext4_warning(sb, "too many blocks added to group %u",
 			     block_group);
 		err = -EINVAL;
 		goto error_return;
@@ -5054,14 +5057,14 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
 	if (err)
 		goto error_return;
 
-	for (i = 0, blocks_freed = 0; i < count; i++) {
+	for (i = 0, clusters_freed = 0; i < cluster_count; i++) {
 		BUFFER_TRACE(bitmap_bh, "clear bit");
 		if (!mb_test_bit(bit + i, bitmap_bh->b_data)) {
 			ext4_error(sb, "bit already cleared for block %llu",
 				   (ext4_fsblk_t)(block + i));
 			BUFFER_TRACE(bitmap_bh, "bit already cleared");
 		} else {
-			blocks_freed++;
+			clusters_freed++;
 		}
 	}
 
@@ -5075,19 +5078,20 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
 	 * them with group lock_held
 	 */
 	ext4_lock_group(sb, block_group);
-	mb_clear_bits(bitmap_bh->b_data, bit, count);
-	mb_free_blocks(NULL, &e4b, bit, count);
-	blk_free_count = blocks_freed + ext4_free_group_clusters(sb, desc);
-	ext4_free_group_clusters_set(sb, desc, blk_free_count);
+	mb_clear_bits(bitmap_bh->b_data, bit, cluster_count);
+	mb_free_blocks(NULL, &e4b, bit, cluster_count);
+	free_clusters_count = clusters_freed +
+		ext4_free_group_clusters(sb, desc);
+	ext4_free_group_clusters_set(sb, desc, free_clusters_count);
 	ext4_block_bitmap_csum_set(sb, block_group, desc, bitmap_bh);
 	ext4_group_desc_csum_set(sb, block_group, desc);
 	ext4_unlock_group(sb, block_group);
 	percpu_counter_add(&sbi->s_freeclusters_counter,
-			   EXT4_NUM_B2C(sbi, blocks_freed));
+			   clusters_freed);
 
 	if (sbi->s_log_groups_per_flex) {
 		ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
-		atomic64_add(EXT4_NUM_B2C(sbi, blocks_freed),
+		atomic64_add(clusters_freed,
 			     &sbi->s_flex_groups[flex_group].free_clusters);
 	}