Re: [PATCH v5 07/13] block: Add PCI P2P flag for request queue and check support for requests

[Logan Gunthorpe]

On 10/09/18 10:41 AM, Christoph Hellwig wrote:
> On Wed, Sep 05, 2018 at 03:03:18PM -0600, Logan Gunthorpe wrote:
>> There is no special p2p submission process. In the nvme-of case we are
>> using the existing process and with the code in blk-core it didn't
>> change it's process at all. Creating a helper will create one and I can
>> look at making a pci_p2pdma_submit_bio() for v6; but if the developer
>> screws up and still calls the regular submit_bio() things will only be
>> very subtly broken and that won't be obvious.
> 
> I just saw you added that "helper" in your tree.  Please don't, it is
> a negative value add as it doesn't help anything with the checking.

Alright, so what's the consensus then? Just have a check in
nvmet_bdev_execute_rw() to add REQ_NOMERGE when appropriate? Jens is
pretty dead set against adding to the common path.

Logan


P.S. Here's the commit in question for anyone else on the list:

https://github.com/sbates130272/linux-p2pmem/commit/eeabe0bc94491d3eec4fe872274a9e3b4cdea538