ext4: remove unnecessary check to avoid repeat update_backups for the same gdb

The sbi->s_group_desc contains array of bh's for block group descriptors
and continuous EXT4_DESC_PER_BLOCK(sb) bg descriptors in single block
share the same bh.
Simply call update_backups for each gdb_bh in sbi->s_group_desc will not
update same group descriptors block for multiple times.

Commit 0acdb887 ("ext4: don't call update_backups() multiple times for
the same bg") wrongly assumed each block group descriptor in the same block
has a individual bh and unnecessary check was added.
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Link: https://lore.kernel.org/r/20230826174712.4059355-13-shikemeng@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ext4.h

@@ -1494,6 +1494,7 @@ struct ext4_sb_info {
 	loff_t s_bitmap_maxbytes;	/* max bytes for bitmap files */
 	struct buffer_head * s_sbh;	/* Buffer containing the super block */
 	struct ext4_super_block *s_es;	/* Pointer to the super block in the buffer */
+	/* Array of bh's for the block group descriptors */
 	struct buffer_head * __rcu *s_group_desc;
 	unsigned int s_mount_opt;
 	unsigned int s_mount_opt2;

fs/ext4/resize.c

@@ -1588,7 +1588,6 @@ static int ext4_flex_group_add(struct super_block *sb,
 		int meta_bg = ext4_has_feature_meta_bg(sb);
 		sector_t padding_blocks = meta_bg ? 0 : sbi->s_sbh->b_blocknr -
 					 ext4_group_first_block_no(sb, 0);
-		sector_t old_gdb = 0;
 
 		update_backups(sb, ext4_group_first_block_no(sb, 0),
 			       (char *)es, sizeof(struct ext4_super_block), 0);
@@ -1597,11 +1596,8 @@ static int ext4_flex_group_add(struct super_block *sb,
 
 			gdb_bh = sbi_array_rcu_deref(sbi, s_group_desc,
 						     gdb_num);
-			if (old_gdb == gdb_bh->b_blocknr)
-				continue;
 			update_backups(sb, gdb_bh->b_blocknr - padding_blocks,
 				       gdb_bh->b_data, gdb_bh->b_size, meta_bg);
-			old_gdb = gdb_bh->b_blocknr;
 		}
 	}
 exit: