Re: [Qemu-devel] [PATCH] honor IDE_DMA_BUF_SECTORS

[Avi Kivity]

Samuel Thibault wrote:
> > But posix read/write does not fit how DMA works.  A request should
> > either complete fully, or fail, leaving the destination (disk or
> > memory) in an undefined state.
> >     
>
> Sure.  Again, please read what _I_ wrote: I'm not proposing to expose
> that into DMA, just make it genericly handled in the block layer.

Okay.  I oppose making short reads part of the API.  Callers should 
expect the return code to be either zero, or a failure indication.

If you want generic block layer support, it could come in the form of 
helpers, that is a block format driver could call 
bdrv_continue_partial_request(lots, of, parameters) to have the helper 
advance the iovec and reissue the partially completed request.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.