commit: 2ebd1704ded88a8ae29b5f3998b13959c715c4be
From: Yongqiang Yang <[email protected]>
Date: Wed, 5 Sep 2012 01:27:50 -0400
Subject: ext4: avoid duplicate writes of the backup bg descriptor blocks

The resize code was needlessly writing the backup block group
descriptor blocks multiple times (once per block group) during an
online resize.

Signed-off-by: Yongqiang Yang <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>
Cc: [email protected]
---
 fs/ext4/resize.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index a0ee26c..365d800 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1358,13 +1358,15 @@ exit_journal:
                err = err2;
 
        if (!err) {
-               int i;
+               int gdb_num = group / EXT4_DESC_PER_BLOCK(sb);
+               int gdb_num_end = ((group + flex_gd->count - 1) /
+                                  EXT4_DESC_PER_BLOCK(sb));
+
                update_backups(sb, sbi->s_sbh->b_blocknr, (char *)es,
                               sizeof(struct ext4_super_block));
-               for (i = 0; i < flex_gd->count; i++, group++) {
+               for (; gdb_num <= gdb_num_end; gdb_num++) {
                        struct buffer_head *gdb_bh;
-                       int gdb_num;
-                       gdb_num = group / EXT4_BLOCKS_PER_GROUP(sb);
+
                        gdb_bh = sbi->s_group_desc[gdb_num];
                        update_backups(sb, gdb_bh->b_blocknr, gdb_bh->b_data,
                                       gdb_bh->b_size);
-- 
1.7.3.4
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