[PATCH 02/13] ext4: add a function which adds a new desc to a fs

[Yongqiang Yang <xiaoqiangnk@gmail.com>]

This patch adds a function named ext4_add_new_desc() which adds
a new desc to a fs and whose code is copied from ext4_group_add().

The function will be used by new resize implementation.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
---
 fs/ext4/resize.c |   42 ++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 42 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 6ffbdb6..4fcd515 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -735,6 +735,48 @@ exit_err:
 	}
 }
 
+/*
+ * ext4_add_new_desc() adds group descriptor of group @group
+ *
+ * @handle: journal handle
+ * @sb; super block
+ * @group: the group no. of the first group desc to be added
+ * @resize_inode: the resize inode
+ */
+static int ext4_add_new_desc(handle_t *handle, struct super_block *sb,
+			     ext4_group_t group, struct inode *resize_inode)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+	struct ext4_super_block *es = sbi->s_es;
+	struct buffer_head *gdb_bh;
+	int gdb_off, gdb_num, err = 0;
+	int reserved_gdb = ext4_bg_has_super(sb, group) ?
+		le16_to_cpu(es->s_reserved_gdt_blocks) : 0;
+
+	gdb_off = group % EXT4_DESC_PER_BLOCK(sb);
+	gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
+
+	/*
+	 * We will only either add reserved group blocks to a backup group
+	 * or remove reserved blocks for the first group in a new group block.
+	 * Doing both would be mean more complex code, and sane people don't
+	 * use non-sparse filesystems anymore.  This is already checked above.
+	 */
+	if (gdb_off) {
+		gdb_bh = sbi->s_group_desc[gdb_num];
+		err = ext4_journal_get_write_access(handle, gdb_bh);
+		if (err)
+			goto out;
+
+		if (reserved_gdb && ext4_bg_num_gdb(sb, group))
+			err = reserve_backup_gdb(handle, resize_inode, group);
+	} else
+		err = add_new_gdb(handle, resize_inode, group);
+
+out:
+	return err;
+}
+
 /* Add group descriptor data to an existing or new group descriptor block.
  * Ensure we handle all possible error conditions _before_ we start modifying
  * the filesystem, because we cannot abort the transaction and not have it
-- 
1.7.5.1