Re: [Qemu-devel] [PATCHv5 3/6] block/iscsi: set max_transfer_length

[Max Reitz <mreitz@redhat.com>]

On 2014-10-27 at 09:47, Peter Lieven wrote:
> On 27.10.2014 09:44, Max Reitz wrote:
>> On 2014-10-27 at 09:36, Peter Lieven wrote:
>>> On 27.10.2014 09:28, Max Reitz wrote:
>>>> On 2014-10-25 at 18:18, Peter Lieven wrote:
>>>>> Copy the max_xfer_len from the BlockLimits VPD or use the
>>>>> maximum value fitting in the CDB.
>>>>>
>>>>> Signed-off-by: Peter Lieven <pl@kamp.de>
>>>>> ---
>>>>>   block/iscsi.c |   17 +++++++++++++++--
>>>>>   1 file changed, 15 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/block/iscsi.c b/block/iscsi.c
>>>>> index 233f462..1ae4add 100644
>>>>> --- a/block/iscsi.c
>>>>> +++ b/block/iscsi.c
>>>>> @@ -297,6 +297,11 @@ static int64_t sector_lun2qemu(int64_t 
>>>>> sector, IscsiLun *iscsilun)
>>>>>       return sector * iscsilun->block_size / BDRV_SECTOR_SIZE;
>>>>>   }
>>>>>   +static int nb_sectors_lun2qemu(int64_t sector, IscsiLun *iscsilun)
>>>>> +{
>>>>> +    return MIN(sector_lun2qemu(sector, iscsilun), INT_MAX);
>>>>> +}
>>>>> +
>>>>>   static int64_t sector_qemu2lun(int64_t sector, IscsiLun *iscsilun)
>>>>>   {
>>>>>       return sector * BDRV_SECTOR_SIZE / iscsilun->block_size;
>>>>> @@ -1449,10 +1454,18 @@ static void iscsi_close(BlockDriverState *bs)
>>>>>     static void iscsi_refresh_limits(BlockDriverState *bs, Error 
>>>>> **errp)
>>>>>   {
>>>>> -    IscsiLun *iscsilun = bs->opaque;
>>>>> -
>>>>>       /* We don't actually refresh here, but just return data 
>>>>> queried in
>>>>>        * iscsi_open(): iscsi targets don't change their limits. */
>>>>> +
>>>>> +    IscsiLun *iscsilun = bs->opaque;
>>>>> +    uint32_t max_xfer_len = iscsilun->use_16_for_rw ? 0xffffffff 
>>>>> : 0xffff;
>>>>> +
>>>>> +    if (iscsilun->bl.max_xfer_len) {
>>>>> +        max_xfer_len = MIN(max_xfer_len, iscsilun->bl.max_xfer_len);
>>>>> +    }
>>>>> +
>>>>> +    bs->bl.max_transfer_length = 
>>>>> nb_sectors_lun2qemu(max_xfer_len, iscsilun);
>>>>> +
>>>>>       if (iscsilun->lbp.lbpu) {
>>>>>           if (iscsilun->bl.max_unmap < 0xffffffff) {
>>>>>               bs->bl.max_discard = 
>>>>> sector_lun2qemu(iscsilun->bl.max_unmap,
>>>>
>>>> Hm, seems strange to have a function called nb_sectors_lun2qemu() 
>>>> not only convert values, but also cap the result. But anyway:
>>>
>>> Would you give it another name?
>>
>> Aaah, looking for names... It's always the same horror...
>>
>> Hm, I just realized why it's nb_sectors, it just wasn't obvious to me 
>> that nb_sectors is always an int (and I think it might not be to 
>> others either).
>>
>> So maybe int_sector_lun2qemu() or even better sector_lun2qemu_int()? 
>> I always consider everything on the left of the "2" to be the 
>> original unit and everything on the right to be the result unit, 
>> maybe that confused me further (so sector_lun2qemu_nb_sectors() is 
>> what I'd expect, although it's rather long).
>>
>> But I now see why you called the function that way and it seems fine 
>> to me. Just leaving it is fine, too. ;-)
>
> what about limits_lun2qemu ? It might give a hint that nobody uses it 
> for sth else than limits?

sector_limits_lun2qemu()? :-)

Max