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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
This commit is contained in:
Yongqiang Yang 2012-09-05 01:25:50 -04:00 committed by Theodore Ts'o
parent d7574ad08b
commit 6df935ad2f
1 changed files with 4 additions and 0 deletions
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4
fs/ext4/resize.c
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@ -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;