On Tue, Jun 17, 2025 at 02:19:11AM +0000, Jason Rahman wrote: > It seems that rather than setting dma_alignment to SECTOR_SIZE - 1 in > md_init_stacking_limits, it should be set to zero, and as > queue_limits_stack_bdev is called on each backing device, the > dma_alignment value will be updated to the largest dma_alignment value > among all backing devices. Are there any thoughts/concerns about > updating the mddev dma_alignment computation to track the underlying > backing device more closely, without the minimum SECTOR_SIZE - 1 lower > bound today? I believe it should be safe to stack dma alignment to the least common multiple of the block devices you're stacking. blk_stack_limits already tries to do that, at least. So I think you're right, it should be okay to not set the dma_alignemnt limit when initializing the stacking limits. For any block device who hasn't set their dma_alignemnt limit, it will default to SECTOR_SIZE - 1 later anyway, so I don't think stacking needs to explicitly initialize it.
