ext4: remove redundant sb checksum recomputation

mainline inclusion
from mainline-v5.11-rc1
commit 81414b4d
category: bugfix
bugzilla: 50839
CVE: NA

-----------------------------------------------

Superblock is written out either through ext4_commit_super() or through
ext4_handle_dirty_super(). In both cases we recompute the checksum so it
is not necessary to recompute it after updating superblock free inodes &
blocks counters.
Signed-off-by: NJan Kara <jack@suse.cz>
Reviewed-by: NAndreas Dilger <adilger@dilger.ca>
Link: https://lore.kernel.org/r/20201127113405.26867-3-jack@suse.czSigned-off-by: NTheodore Ts'o <tytso@mit.edu>
Signed-off-by: NYe Bin <yebin10@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/ext4/super.c

@@ -5003,13 +5003,11 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	block = ext4_count_free_clusters(sb);
 	ext4_free_blocks_count_set(sbi->s_es, 
 				   EXT4_C2B(sbi, block));
-	ext4_superblock_csum_set(sb);
 	err = percpu_counter_init(&sbi->s_freeclusters_counter, block,
 				  GFP_KERNEL);
 	if (!err) {
 		unsigned long freei = ext4_count_free_inodes(sb);
 		sbi->s_es->s_free_inodes_count = cpu_to_le32(freei);
-		ext4_superblock_csum_set(sb);
 		err = percpu_counter_init(&sbi->s_freeinodes_counter, freei,
 					  GFP_KERNEL);
 	}