[PATCH v3 1/3] ext4: fix bad checksum after online resize

[Baokun Li]

When online resizing is performed twice consecutively, the error message
"Superblock checksum does not match superblock" is displayed for the
second time. Here's the reproducer:

	mkfs.ext4 -F /dev/sdb 100M
	mount /dev/sdb /tmp/test
	resize2fs /dev/sdb 5G
	resize2fs /dev/sdb 6G

To solve this issue, we moved the update of the checksum after the
es->s_overhead_clusters is updated.

Fixes: 026d0d27c488 ("ext4: reduce computation of overhead during resize")
Fixes: de394a86658f ("ext4: update s_overhead_clusters in the superblock during an on-line resize")
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
 fs/ext4/resize.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 46b87ffeb304..cb99b410c9fa 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1476,8 +1476,6 @@ static void ext4_update_super(struct super_block *sb,
 	 * active. */
 	ext4_r_blocks_count_set(es, ext4_r_blocks_count(es) +
 				reserved_blocks);
-	ext4_superblock_csum_set(sb);
-	unlock_buffer(sbi->s_sbh);
 
 	/* Update the free space counts */
 	percpu_counter_add(&sbi->s_freeclusters_counter,
@@ -1513,6 +1511,8 @@ static void ext4_update_super(struct super_block *sb,
 		ext4_calculate_overhead(sb);
 	es->s_overhead_clusters = cpu_to_le32(sbi->s_overhead);
 
+	ext4_superblock_csum_set(sb);
+	unlock_buffer(sbi->s_sbh);
 	if (test_opt(sb, DEBUG))
 		printk(KERN_DEBUG "EXT4-fs: added group %u:"
 		       "%llu blocks(%llu free %llu reserved)\n", flex_gd->count,
-- 
2.31.1