Re: [Qemu-devel] [Qemu-block] [PATCH] block: document semanatics of bdrv_co_preadv|pwritev

[Eric Blake <eblake@redhat.com>]

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On 08/08/2017 04:13 AM, Daniel P. Berrange wrote:
> On Tue, Aug 08, 2017 at 10:39:29AM +0800, Fam Zheng wrote:
>> On Fri, 08/04 16:49, Daniel P. Berrange wrote:
>>> This is odd.  In the bdrv_aligned_readv() it looks very much like
>>> we'll reference qiov->niov, if bytes != 0, so if qiov was NULL we
>>> would crash.
>>
>> It doesn't make sense if read doesn't have an iov, where should the data be
>> placed? :)
>>

> We can't remove it from the bdrv_co_pwritev() function, but we can remove
> it from bdrv_co_pwritev block driver callback AFAICT.

Sounds like a separate cleanup series to remove the length parameter for
both read and write (since we have write_zeroes), for the 2.11
timeframe.  You're right that the block layer does not have to have
quite the same interface as the driver callbacks.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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