Commit 6df935ad authored Sep 05, 2012 by Yongqiang Yang Committed by Theodore Ts'o Sep 05, 2012

ext4: don't copy non-existent gdt blocks when resizing



The resize code was copying blocks at the beginning of each block
group in order to copy the superblock and block group descriptor table
(gdt) blocks.  This was, unfortunately, being done even for block
groups that did not have super blocks or gdt blocks.  This is a
complete waste of perfectly good I/O bandwidth, to skip writing those
blocks for sparse bg's.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

parent d7574ad0

fs/ext4/resize.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -456,6 +456,9 @@ static int setup_new_flex_group_blocks(struct super_block *sb,
		gdblocks = ext4_bg_num_gdb(sb, group);
		start = ext4_group_first_block_no(sb, group);

		if (!ext4_bg_has_super(sb, group))
		goto handle_itb;

		/* 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;
		@@ -498,6 +501,7 @@ static int setup_new_flex_group_blocks(struct super_block *sb,
		goto out;
		}

		handle_itb:
		/* Initialize group tables of the grop @group */
		if (!(bg_flags[i] & EXT4_BG_INODE_ZEROED))
		goto handle_bb;