[PATCH net-next v3 10/18] nvme/host: Use sendmsg(MSG_SPLICE_PAGES) rather then sendpage

[Sagi Grimberg]

> Hi David,
> 
> David Howells <dhowells at redhat.com> writes:
>> When transmitting data, call down into TCP using a single sendmsg with
>> MSG_SPLICE_PAGES to indicate that content should be spliced rather than
>> performing several sendmsg and sendpage calls to transmit header, data
>> pages and trailer.
> 
> This series makes my kernel crash.
> 
>  From the current net-next main branch:
> 
> commit 9ae440b8fdd6772b6c007fa3d3766530a09c9045 (HEAD)
> Merge: b545a13ca9b2 b848b26c6672
> Author: Jakub Kicinski <kuba at kernel.org>
> Date:   Sat Jun 24 15:50:21 2023 -0700
> 
>      Merge branch 'splice-net-switch-over-users-of-sendpage-and-remove-it'
> 
> 
> Steps to reproduce:
> 
> * connect a remote nvme null block device (nvmet) with 1 IO queue to keep
>    things simple
> * open /dev/nvme0n1 with O_RDWR|O_DIRECT|O_SYNC
> * write() a 8k buffer or 4k buffer

Most likely this also reproduces with blktests?
https://github.com/osandov/blktests

simple way to check is to run:
nvme_trtype=tcp ./check nvme

This runs nvme tests over nvme-tcp.

No need for network, disk or anything. It runs
both nvme and nvmet over the lo device..