Re: [BUG] discard_granularity is 0 on rk3399-gru-kevin

[Vicente Bergas <vicencb@gmail.com>]

On Monday, September 28, 2020 7:02:00 AM CEST, Coly Li wrote:
> On 2020/9/28 11:15, Coly Li wrote:
>> On 2020/9/28 04:29, Vicente Bergas wrote:
>>> Hi,
>>> since recently the rk3399-gru-kevin is reporting the trace below.
>>> The issue has been uncovered by
>>>  b35fd7422c2f8e04496f5a770bd4e1a205414b3f
>>>  block: check queue's limits.discard_granularity in ...
>> 
>> Hi Vicente,
>> 
>> Thanks for the information. It seems the device with f2fs declares to
>> support DISCARD but don't initialize discard_granularity for its queue.
>> 
>> Can I know which block driver is under f2fs ?

Hi Coly, yes, i confirm it is the mmc driver.
Regards,
  Vicente.

> Maybe it is the mmc driver. A zero value discard_granularity is from the
> following commit:
>
> commit e056a1b5b67b4e4bfad00bf143ab14f634777705
> Author: Adrian Hunter <adrian.hunter@intel.com>
> Date:   Tue Jun 28 17:16:02 2011 +0300
>
>     mmc: queue: let host controllers specify maximum discard timeout
>
>     Some host controllers will not operate without a hardware
>     timeout that is limited in value.  However large discards
>     require large timeouts, so there needs to be a way to
>     specify the maximum discard size.
>
>     A host controller driver may now specify the maximum discard
>     timeout possible so that max_discard_sectors can be calculated.
>
>     However, for eMMC when the High Capacity Erase Group Size
>     is not in use, the timeout calculation depends on clock
>     rate which may change.  For that case Preferred Erase Size
>     is used instead.
>
>     Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
>     Signed-off-by: Chris Ball <cjb@laptop.org>
>
>
> Hi Adrian and Chris,
>
> I am not familiar with mmc driver, therefore I won't provide a quick fix
> like this (which might probably wrong),
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -190,7 +190,7 @@ static void mmc_queue_setup_discard(struct
> request_queue *q,
>         q->limits.discard_granularity = card->pref_erase << 9;
>         /* granularity must not be greater than max. discard */
>         if (card->pref_erase > max_discard)
> -               q->limits.discard_granularity = 0;
> +               q->limits.discard_granularity = SECTOR_SIZE;
>         if (mmc_can_secure_erase_trim(card))
>                 blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);
>  }
>
>
> It is improper for a device driver to declare to support DISCARD but set
> queue's discard_granularity as 0.
>
> Could you please to take a look for mmc_queue_setup_discard() ?
>
> Thanks in advance.
>
> Coly Li
>
>
>>  ...
>
>
>


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