[PATCH v11 06/13] block: modify the comment for BDRV_REQ_PREFETCH flag

[Vladimir Sementsov-Ogievskiy]

14.10.2020 15:22, Max Reitz wrote:
> On 12.10.20 19:43, Andrey Shinkevich wrote:
>> Modify the comment for the flag BDRV_REQ_PREFETCH as we are going to
>> use it alone and pass it to the COR-filter driver for further
>> processing.
>>
>> Signed-off-by: Andrey Shinkevich <andrey.shinkevich at virtuozzo.com>
>> ---
>>   include/block/block.h | 7 ++++---
>>   1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/block/block.h b/include/block/block.h
>> index 981ab5b..2b7efd1 100644
>> --- a/include/block/block.h
>> +++ b/include/block/block.h
>> @@ -71,9 +71,10 @@ typedef enum {
>>       BDRV_REQ_NO_FALLBACK        = 0x100,
>>   
>>       /*
>> -     * BDRV_REQ_PREFETCH may be used only together with BDRV_REQ_COPY_ON_READ
>> -     * on read request and means that caller doesn't really need data to be
>> -     * written to qiov parameter which may be NULL.
>> +     * BDRV_REQ_PREFETCH may be used together with the BDRV_REQ_COPY_ON_READ
>> +     * flag or when the COR-filter applied to read operations and means that
> 
> There’s some word missing here, but I’m not sure what it is...  At least
> an “is” before “applied”.  Perhaps something like ”or when a COR filter
> is involved (in read operations)” would be better.
> 
>> +     * caller doesn't really need data to be written to qiov parameter which
> 
> And this “written to” confused me for a second, because we’re reading
> into qiov.  Technically, that means writing into the buffer, but, you know.
> 
> Could we rewrite the whole thing, perhaps?  Something like
> 
> “BDRV_REQ_PREFETCH makes sense only in the context of copy-on-read
> (i.e., together with the BDRV_REQ_COPY_ON_READ flag or when there is a
> COR filter), in which case it signals that the COR operation need not
> read the data into memory (qiov), but only ensure it is copied to the
> top layer (i.e., that COR is done).”
> 

Sounds good

> 
>> +     * may be NULL.
>>        */
>>       BDRV_REQ_PREFETCH  = 0x200,
>>       /* Mask of valid flags */
>>
> 
> 


-- 
Best regards,
Vladimir