On 2022-09-26 18:32, Jens Axboe wrote: > On 9/26/22 8:43 AM, Christoph Hellwig wrote: >> On Mon, Sep 26, 2022 at 08:40:54AM -0600, Jens Axboe wrote: >>> On 9/26/22 8:37 AM, Christoph Hellwig wrote: >>>> On Sun, Sep 25, 2022 at 08:53:46PM +0200, Pankaj Raghav wrote: >>>>> Modify blk_mq_plug() to allow plugging only for read operations in zoned >>>>> block devices as there are alternative IO paths in the linux block >>>>> layer which can end up doing a write via driver private requests in >>>>> sequential write zones. >>>> >>>> We should be able to plug for all operations that are not >>>> REQ_OP_ZONE_APPEND just fine. >>> >>> Agree, I think we just want to make this about someone doing a series >>> of appends. If you mix-and-match with passthrough you will have a bad >>> time anyway. >> >> Err, sorry - what I wrote about is compelte garbage. I initially >> wanted to say you can plug for REQ_OP_ZONE_APPEND just fine, and then >> realized that we also want various other ones that have the write bit >> set batched. So I suspect we really want to explicitly check for >> REQ_OP_WRITE here. > > My memory was a bit hazy, since we have separate ops for the driver > in/out, I think just checking for REQ_OP_WRITE is indeed the right > choice. That's the single case we need to care about. > Ah. You are right. I missed it as well. There is even a comment from Christoph: * - if the least significant bit is set transfers are TO the device * - if the least significant bit is not set transfers are FROM the device I guess the second patch should be enough to apply plugging when applicable for uring_cmd based nvme passthrough requests.
