Re: [Qemu-block] [Qemu-devel] [PATCH v2 3/3] block: add default implementations for bdrv_co_get_block_status()

[Eric Blake]

On 07/03/2017 01:24 PM, Manos Pitsidianakis wrote:

>> In fact, my rebase fallout is to completely delete
>> bdrv_co_get_block_status_from_file().  Why? Because blkdebug is the only
>> client, but I want to enhance blkdebug to add in-place assert()ions that
>> the values passed by the block layer are properly aligned to
>> bs->bl.request_alignment (matching what blkdebug does for read and write
>> - after all, if a device cannot access smaller than a given alignment
>> for a read, it should not be able to report different statuses half-way
>> through that granularity).  However, in-place assertions are no longer
>> generic, so we no longer have a client of a generic helper function
>> referring to bs->file.
>>
>> Which means you are REALLY left only with commit and mirror as the two
>> functions that have a common implementation of pointing back to backing.
> 
> 
> Hello Eric, thanks for taking the time to review my patches.
> 
> The throttle driver I'm working on passes bdrv_co_get_block_status() to
> bs->file. If there is a problem with an unused default function (it's
> not static so will compile, but it might not be up to standard), you can
> just remove it and I will reintroduce it when it's needed. CC me on
> those patches when you send them if you can.

Sure. The other thing I can do is have:

blkdebug_version() {
   assert(...);
   return common version;
}

so that the common version is still there for use by the throttling
code.  I'm adjusting my rebase accordingly, now that I know you have
another intended use in mind.

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

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