Re: [PATCH v7] NVMe: conversion to blk-mq

Matthew Wilcox
2014-06-10T21:33:36Z

On Tue, Jun 10, 2014 at 03:21:18PM -0600, Keith Busch wrote:
> Yeah, nvme_setup_prps is probably the least readable code in this driver.
> Maybe some comments are in order here...
>
> There are two rules for an SGL to be mappable to a PRP:
>
> 1. Every element must have zero page offset, except the first.
>
> 2. Every element must end on a page boundary, except the last.

Or to put it another way, NVMe PRPs only support I/Os that describe a
single range of virtual memory.