ext4: enable dioread_nolock as default for bs < ps case

dioread_nolock was originally disabled as a default option for bs < ps
scenarios due to a data corruption issue. Since then, we've had some
fixes in this area which address such issues. Enable dioread_nolock by
default and remove the experimental warning message for bs < ps path.

dioread for bs < ps has been tested on a 64k pagesize machine using:

kvm-xfstest -C 3 -g auto

with the following configs:

64k adv bigalloc_4k bigalloc_64k data_journal encrypt
dioread_nolock dioread_nolock_4k ext3 ext3conv nojournal

And no new regressions were seen compared to baseline kernel.

Suggested-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20231101154717.531865-1-ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: OjaswinM

fs/ext4/super.c

@@ -2793,15 +2793,6 @@ static int ext4_check_opt_consistency(struct fs_context *fc,
 		return -EINVAL;
 	}
 
-	if (ctx_test_mount_opt(ctx, EXT4_MOUNT_DIOREAD_NOLOCK)) {
-		int blocksize =
-			BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);
-		if (blocksize < PAGE_SIZE)
-			ext4_msg(NULL, KERN_WARNING, "Warning: mounting with an "
-				 "experimental mount option 'dioread_nolock' "
-				 "for blocksize < PAGE_SIZE");
-	}
-
 	err = ext4_check_test_dummy_encryption(fc, sb);
 	if (err)
 		return err;
@@ -4410,7 +4401,7 @@ static void ext4_set_def_opts(struct super_block *sb,
 	    ((def_mount_opts & EXT4_DEFM_NODELALLOC) == 0))
 		set_opt(sb, DELALLOC);
 
-	if (sb->s_blocksize == PAGE_SIZE)
+	if (sb->s_blocksize <= PAGE_SIZE)
 		set_opt(sb, DIOREAD_NOLOCK);
 }