md: Fix logical_block_size configuration being overwritten

In super_1_validate(), mddev->logical_block_size is directly overwritten
with the value from metadata. This causes the previously configured lbs
to be lost, making the configuration ineffective. Fix it.

Fixes: 62ed1b5 ("md: allow configuring logical block size")
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Link: https://lore.kernel.org/linux-raid/20251226024221.724201-1-linan666@huaweicloud.com
Signed-off-by: Yu Kuai <yukuai@fnnas.com>

Author: Li Nan

drivers/md/md.c

@@ -1999,7 +1999,6 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
 		mddev->layout = le32_to_cpu(sb->layout);
 		mddev->raid_disks = le32_to_cpu(sb->raid_disks);
 		mddev->dev_sectors = le64_to_cpu(sb->size);
-		mddev->logical_block_size = le32_to_cpu(sb->logical_block_size);
 		mddev->events = ev1;
 		mddev->bitmap_info.offset = 0;
 		mddev->bitmap_info.space = 0;
@@ -2015,6 +2014,9 @@ static int super_1_validate(struct mddev *mddev, struct md_rdev *freshest, struc
 
 		mddev->max_disks =  (4096-256)/2;
 
+		if (!mddev->logical_block_size)
+			mddev->logical_block_size = le32_to_cpu(sb->logical_block_size);
+
 		if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BITMAP_OFFSET) &&
 		    mddev->bitmap_info.file == NULL) {
 			mddev->bitmap_info.offset =