ext4: add a function which sets up group blocks of a flex bg

This patch adds a function named setup_new_flex_group_blocks() which
sets up group blocks of a flex bg.
Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -511,6 +511,14 @@ struct ext4_new_group_data {
 	__u32 free_blocks_count;
 };
 
+/* Indexes used to index group tables in ext4_new_group_data */
+enum {
+	BLOCK_BITMAP = 0,	/* block bitmap */
+	INODE_BITMAP,		/* inode bitmap */
+	INODE_TABLE,		/* inode tables */
+	GROUP_TABLE_COUNT,
+};
+
 /*
  * Flags used by ext4_map_blocks()
  */

fs/ext4/resize.c

@@ -233,6 +233,256 @@ static int extend_or_restart_transaction(handle_t *handle, int thresh)
 	return 0;
 }
 
+/*
+ * set_flexbg_block_bitmap() mark @count blocks starting from @block used.
+ *
+ * Helper function for ext4_setup_new_group_blocks() which set .
+ *
+ * @sb: super block
+ * @handle: journal handle
+ * @flex_gd: flex group data
+ */
+static int set_flexbg_block_bitmap(struct super_block *sb, handle_t *handle,
+			struct ext4_new_flex_group_data *flex_gd,
+			ext4_fsblk_t block, ext4_group_t count)
+{
+	ext4_group_t count2;
+
+	ext4_debug("mark blocks [%llu/%u] used\n", block, count);
+	for (count2 = count; count > 0; count -= count2, block += count2) {
+		ext4_fsblk_t start;
+		struct buffer_head *bh;
+		ext4_group_t group;
+		int err;
+
+		ext4_get_group_no_and_offset(sb, block, &group, NULL);
+		start = ext4_group_first_block_no(sb, group);
+		group -= flex_gd->groups[0].group;
+
+		count2 = sb->s_blocksize * 8 - (block - start);
+		if (count2 > count)
+			count2 = count;
+
+		if (flex_gd->bg_flags[group] & EXT4_BG_BLOCK_UNINIT) {
+			BUG_ON(flex_gd->count > 1);
+			continue;
+		}
+
+		err = extend_or_restart_transaction(handle, 1);
+		if (err)
+			return err;
+
+		bh = sb_getblk(sb, flex_gd->groups[group].block_bitmap);
+		if (!bh)
+			return -EIO;
+
+		err = ext4_journal_get_write_access(handle, bh);
+		if (err)
+			return err;
+		ext4_debug("mark block bitmap %#04llx (+%llu/%u)\n", block,
+			   block - start, count2);
+		ext4_set_bits(bh->b_data, block - start, count2);
+
+		err = ext4_handle_dirty_metadata(handle, NULL, bh);
+		if (unlikely(err))
+			return err;
+		brelse(bh);
+	}
+
+	return 0;
+}
+
+/*
+ * Set up the block and inode bitmaps, and the inode table for the new groups.
+ * This doesn't need to be part of the main transaction, since we are only
+ * changing blocks outside the actual filesystem.  We still do journaling to
+ * ensure the recovery is correct in case of a failure just after resize.
+ * If any part of this fails, we simply abort the resize.
+ *
+ * setup_new_flex_group_blocks handles a flex group as follow:
+ *  1. copy super block and GDT, and initialize group tables if necessary.
+ *     In this step, we only set bits in blocks bitmaps for blocks taken by
+ *     super block and GDT.
+ *  2. allocate group tables in block bitmaps, that is, set bits in block
+ *     bitmap for blocks taken by group tables.
+ */
+static int setup_new_flex_group_blocks(struct super_block *sb,
+				struct ext4_new_flex_group_data *flex_gd)
+{
+	int group_table_count[] = {1, 1, EXT4_SB(sb)->s_itb_per_group};
+	ext4_fsblk_t start;
+	ext4_fsblk_t block;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_super_block *es = sbi->s_es;
+	struct ext4_new_group_data *group_data = flex_gd->groups;
+	__u16 *bg_flags = flex_gd->bg_flags;
+	handle_t *handle;
+	ext4_group_t group, count;
+	struct buffer_head *bh = NULL;
+	int reserved_gdb, i, j, err = 0, err2;
+
+	BUG_ON(!flex_gd->count || !group_data ||
+	       group_data[0].group != sbi->s_groups_count);
+
+	reserved_gdb = le16_to_cpu(es->s_reserved_gdt_blocks);
+
+	/* This transaction may be extended/restarted along the way */
+	handle = ext4_journal_start_sb(sb, EXT4_MAX_TRANS_DATA);
+	if (IS_ERR(handle))
+		return PTR_ERR(handle);
+
+	group = group_data[0].group;
+	for (i = 0; i < flex_gd->count; i++, group++) {
+		unsigned long gdblocks;
+
+		gdblocks = ext4_bg_num_gdb(sb, group);
+		start = ext4_group_first_block_no(sb, group);
+
+		/* Copy all of the GDT blocks into the backup in this group */
+		for (j = 0, block = start + 1; j < gdblocks; j++, block++) {
+			struct buffer_head *gdb;
+
+			ext4_debug("update backup group %#04llx\n", block);
+			err = extend_or_restart_transaction(handle, 1);
+			if (err)
+				goto out;
+
+			gdb = sb_getblk(sb, block);
+			if (!gdb) {
+				err = -EIO;
+				goto out;
+			}
+
+			err = ext4_journal_get_write_access(handle, gdb);
+			if (err) {
+				brelse(gdb);
+				goto out;
+			}
+			memcpy(gdb->b_data, sbi->s_group_desc[j]->b_data,
+			       gdb->b_size);
+			set_buffer_uptodate(gdb);
+
+			err = ext4_handle_dirty_metadata(handle, NULL, gdb);
+			if (unlikely(err)) {
+				brelse(gdb);
+				goto out;
+			}
+			brelse(gdb);
+		}
+
+		/* Zero out all of the reserved backup group descriptor
+		 * table blocks
+		 */
+		if (ext4_bg_has_super(sb, group)) {
+			err = sb_issue_zeroout(sb, gdblocks + start + 1,
+					reserved_gdb, GFP_NOFS);
+			if (err)
+				goto out;
+		}
+
+		/* Initialize group tables of the grop @group */
+		if (!(bg_flags[i] & EXT4_BG_INODE_ZEROED))
+			goto handle_bb;
+
+		/* Zero out all of the inode table blocks */
+		block = group_data[i].inode_table;
+		ext4_debug("clear inode table blocks %#04llx -> %#04lx\n",
+			   block, sbi->s_itb_per_group);
+		err = sb_issue_zeroout(sb, block, sbi->s_itb_per_group,
+				       GFP_NOFS);
+		if (err)
+			goto out;
+
+handle_bb:
+		if (bg_flags[i] & EXT4_BG_BLOCK_UNINIT)
+			goto handle_ib;
+
+		/* Initialize block bitmap of the @group */
+		block = group_data[i].block_bitmap;
+		err = extend_or_restart_transaction(handle, 1);
+		if (err)
+			goto out;
+
+		bh = bclean(handle, sb, block);
+		if (IS_ERR(bh)) {
+			err = PTR_ERR(bh);
+			goto out;
+		}
+		if (ext4_bg_has_super(sb, group)) {
+			ext4_debug("mark backup superblock %#04llx (+0)\n",
+				   start);
+			ext4_set_bits(bh->b_data, 0, gdblocks + reserved_gdb +
+						     1);
+		}
+		ext4_mark_bitmap_end(group_data[i].blocks_count,
+				     sb->s_blocksize * 8, bh->b_data);
+		err = ext4_handle_dirty_metadata(handle, NULL, bh);
+		if (err)
+			goto out;
+		brelse(bh);
+
+handle_ib:
+		if (bg_flags[i] & EXT4_BG_INODE_UNINIT)
+			continue;
+
+		/* Initialize inode bitmap of the @group */
+		block = group_data[i].inode_bitmap;
+		err = extend_or_restart_transaction(handle, 1);
+		if (err)
+			goto out;
+		/* Mark unused entries in inode bitmap used */
+		bh = bclean(handle, sb, block);
+		if (IS_ERR(bh)) {
+			err = PTR_ERR(bh);
+			goto out;
+		}
+
+		ext4_mark_bitmap_end(EXT4_INODES_PER_GROUP(sb),
+				     sb->s_blocksize * 8, bh->b_data);
+		err = ext4_handle_dirty_metadata(handle, NULL, bh);
+		if (err)
+			goto out;
+		brelse(bh);
+	}
+	bh = NULL;
+
+	/* Mark group tables in block bitmap */
+	for (j = 0; j < GROUP_TABLE_COUNT; j++) {
+		count = group_table_count[j];
+		start = (&group_data[0].block_bitmap)[j];
+		block = start;
+		for (i = 1; i < flex_gd->count; i++) {
+			block += group_table_count[j];
+			if (block == (&group_data[i].block_bitmap)[j]) {
+				count += group_table_count[j];
+				continue;
+			}
+			err = set_flexbg_block_bitmap(sb, handle,
+						flex_gd, start, count);
+			if (err)
+				goto out;
+			count = group_table_count[j];
+			start = group_data[i].block_bitmap;
+			block = start;
+		}
+
+		if (count) {
+			err = set_flexbg_block_bitmap(sb, handle,
+						flex_gd, start, count);
+			if (err)
+				goto out;
+		}
+	}
+
+out:
+	brelse(bh);
+	err2 = ext4_journal_stop(handle);
+	if (err2 && !err)
+		err = err2;
+
+	return err;
+}
+
 /*
  * Set up the block and inode bitmaps, and the inode table for the new group.
  * This doesn't need to be part of the main transaction, since we are only