ext4: avoid duplicate writes of the backup bg descriptor blocks

commit 2ebd1704ded88a8ae29b5f3998b13959c715c4be upstream.

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 <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 1afd3e735459abbd90a45936fb994b26b8f589a7..0be1789ebc3ba7dd95da8a571e4ee1b073362865 100644 (file)
--- 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);