On Thu, Oct 18, 2018 at 08:27:28AM -0600, Jens Axboe wrote:

On 10/18/18 7:18 AM, Ming Lei wrote:

quoted

Now we only check if DMA IO buffer is aligned to queue_dma_alignment()
for pass-through request, and it isn't done for normal IO request.

Given the check has to be done on each bvec, it isn't efficient to add the
check in generic_make_request_checks().

This patch addes one WARN in blk_queue_split() for capturing this issue.

I don't want to do this, because then we are forever doomed to
have something that fully loops a bio at submission time. I
absolutely hate the splitting we have and the need for it,
hopefully it can go away for a subset of IOs at some point.

It is just a WARN_ON - no one should rely on it, but it is a good
debug aid.