Re: [PATCH] blkif.h: enhance comments related to the discard feature

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 14.01.14 at 22:57, Olaf Hering <olaf@aepfle.de> wrote:
>> Also fix the name of the discard-alignment property, add the missing
>'n'.
>> 
>> Signed-off-by: Olaf Hering <olaf@aepfle.de>
>
>Konrad,
>
>you have been working on the discard stuff quite a bit iirc - any
>chance you could take a look and send and ack/review?

Sure - next week I will dig through the patches.
>
>Jan
>
>> ---
>>  xen/include/public/io/blkif.h | 16 ++++++++++++----
>>  1 file changed, 12 insertions(+), 4 deletions(-)
>> 
>> diff --git a/xen/include/public/io/blkif.h
>b/xen/include/public/io/blkif.h
>> index 84eb7fd..515ea90 100644
>> --- a/xen/include/public/io/blkif.h
>> +++ b/xen/include/public/io/blkif.h
>> @@ -175,7 +175,7 @@
>>   *
>>   *------------------------- Backend Device Properties
>-------------------------
>>   *
>> - * discard-aligment
>> + * discard-alignment
>>   *      Values:         <uint32_t>
>>   *      Default Value:  0
>>   *      Notes:          4, 5
>> @@ -194,6 +194,7 @@
>>   * discard-secure
>>   *      Values:         0/1 (boolean)
>>   *      Default Value:  0
>> + *      Notes:          10
>>   *
>>   *      A value of "1" indicates that the backend can process 
>> BLKIF_OP_DISCARD
>>   *      requests with the BLKIF_DISCARD_SECURE flag set.
>> @@ -323,9 +324,14 @@
>>   *     For full interoperability, block front and backends should
>publish
>>   *     identical ring parameters, adjusted for unit differences, to
>the
>>   *     XenStore nodes used in both schemes.
>> - * (4) Devices that support discard functionality may internally
>allocate
>> - *     space (discardable extents) in units that are larger than the
>> - *     exported logical block size.
>> + * (4) Devices that support discard functionality may internally
>allocate 
>> space
>> + *     (discardable extents) in units that are larger than the
>exported 
>> logical
>> + *     block size. If the backing device has such discardable
>extents the
>> + *     backend must provide both discard-granularity and
>discard-alignment.
>> + *     Backends supporting discard should include
>discard-granularity and
>> + *     discard-alignment even if it supports discarding individual
>sectors.
>> + *     Frontends should assume discard-alignment == 0 and
>discard-granularity 
>> ==
>> + *     sector size if these keys are missing.
>>   * (5) The discard-alignment parameter allows a physical device to
>be
>>   *     partitioned into virtual devices that do not necessarily
>begin or
>>   *     end on a discardable extent boundary.
>> @@ -344,6 +350,8 @@
>>   *     grants that can be persistently mapped in the frontend
>driver, but
>>   *     due to the frontent driver implementation it should never be
>bigger
>>   *     than RING_SIZE * BLKIF_MAX_SEGMENTS_PER_REQUEST.
>> + *(10) The discard-secure property may be present and will be set to
>1 if 
>> the
>> + *     backing device supports secure discard.
>>   */
>>  
>>  /*
>> 
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