[RFC 0/4] partial sector read support

[Sagi Grimberg]

> From: Keith Busch <kbusch at kernel.org>
> 
> Don't you just hate that you must read a full sector when you only cared
> about a few bytes? Well, good news! Standardized protocols provide a way
> for the host to describe unwanted read data, allowing partial sector
> access. This lets applications reduce allocated memory that was used to
> hold the unwanted data, while also reducing link traffic.
> 
> This series enables this for the NVMe protocol through direct io. With
> this, a userspace app can read a single contiguous byte range, subject
> to hardware DMA constraints. An in-kernel user could theorectically
> construct a bio to read multiple discontiguous ranges if desired.

So userspace needs to look for both bb queue flag and dma alignment to
infer supported range(s)?