How to resolve an issue in swiotlb environment?

[Christoph Hellwig]

On Wed, Jun 12, 2019 at 10:43:11AM -0400, Alan Stern wrote:
> Would it be okay to rely on the assumption that USB block devices never 
> have block size < 512?  (We could even add code to the driver to 
> enforce this, although refusing to handle such devices at all might be 
> worse than getting an occasional error.)

sd.c only supports a few specific sector size, and none of them is
< 512 bytes:

	if (sector_size != 512 &&
	    sector_size != 1024 &&
	    sector_size != 2048 &&
	    sector_size != 4096) {
	    	...
		sdkp->capacity = 0;