On 10/18/18 7:18 AM, Ming Lei wrote: > 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. In many ways, this seems to be somewhat of a made-up problem, I don't recall a single bug report for something like this over decades of working with the IO stack. 512b alignment restrictions for DMA seems absolutely insane. I know people claim they exist, but clearly that isn't a hard requirement or we would have been boned years ago. -- Jens Axboe
