Re: [Qemu-devel] [PATCH 1/3] Add specialized block driver scsi generic API

[Avi Kivity]

Christoph Hellwig wrote:
> Hower the way the new
> API is designed somewhat gets in the way of my patch series to support
> Gerd's native preadv/pwritev.
>
>   

Can you point out specific issues?

> One thing I wonder is why we go through the block layer at all for SG.
> It is actually backed by a char device that doesn't have semantics like
> a block device at all, given that it can't be seekend and is accessed
> at byte granularity.  We could just go directly to the native Linus
> syscalls from scsi-generic.c (or a scsi-generic-linux.c if we want
> some level of abstraction).  I'll cook up a patch trying that once I'm
> back home

Using the block layer has the advantage of common setup, statistics, and 
management.  I agree that the actual data movement is horribly out of 
sync with the other format drivers.

Come to think of it, I don't see how statistics can work, so maybe it is 
a good idea to separate the two paths completely.

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