linux-kernel - Re: [PATCH v2] mmc: block: enable cache-flushing when mmc cache is on

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Date:   Tue, 19 Apr 2022 22:59:48 +0800
From:   Michael Wu <michael@...winnertech.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     axboe@...nel.dk, adrian.hunter@...el.com, avri.altman@....com,
        kch@...dia.com, beanhuo@...ron.com, swboyd@...omium.org,
        digetx@...il.com, bigeasy@...utronix.de, CLoehle@...erstone.com,
        cjb@...top.org, arnd@...db.de, andreiw@...orola.com,
        tgih.jun@...sung.com, jh80.chung@...sung.com,
        linus.walleij@...aro.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        allwinner-opensource-support@...winnertech.com
Subject: Re: [PATCH v2] mmc: block: enable cache-flushing when mmc cache is on

On 04/04/2022 19:52, Ulf Hansson wrote:
> On Thu, 31 Mar 2022 at 09:32, Michael Wu <michael@...winnertech.com> wrote:
>>
>> The mmc core enables cache by default. But it only enables
>> cache-flushing when host supports cmd23 and eMMC supports
>> reliable-write.
>> For hosts which do not support cmd23 or eMMCs which do not support
>> reliable-write, the cache can not be flushed by `sync` command.
>> This may leads to cache data lost.
>> This patch enables cache-flushing as long as cache is enabled,
>> no matter host supports cmd23 and/or eMMC supports reliable write
>> or not.
>> For SD cards, backwards compatibility is guaranteed. Newer components
>> like SD5.0 which have cache are also supported in advance, which means
>> this patch will also be applicable if SD5.0 cache is added to the mmc
>> core in the future.
> 
> SD 5.0 cache support was added in the commit 130206a615a9 below. No
> need to resend, I will take care of updating the commit message.
> >>
>> Fixes: f4c5522b0a88 ("mmc: Reliable write support.")
>> Fixes: 881d1c25f765 ("mmc: core: Add cache control for eMMC4.5 device")
>> Fixes: 130206a615a9 ("mmc: core: Add support for cache ctrl for SD cards")
>> Fixes: d0c97cfb81eb ("mmc: core: Use CMD23 for multiblock transfers when we can.")
>> Fixes: e9d5c746246c ("mmc/block: switch to using blk_queue_write_cache()")
> 
> I will have a look at the above to see what makes sense to add - and
> then I will add a stable tag too.
> 
Dear Ulf,
Thank you for your effort. I saw this patch which was taken care by you 
on the mainline [commit 08ebf903af57], and also the commits in 
stable-queque by Greg-KH. I guess this means this patch is accepted/closed.
I'm so happy and want to say thank you for all the help. Next time I'm 
sure I'll do it better :)

-- 
Best Regards,
Michael Wu

>>
>> Reviewed-by: Avri Altman <Avri.Altman@....com>
>> Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
>>
>> Signed-off-by: Michael Wu <michael@...winnertech.com>
> 
> Thanks, applied for fixes!
> 
> Kind regards
> Uffe
> 
> 
>> ---
>>   drivers/mmc/core/block.c | 12 +++++++++---
>>   1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
>> index 4e67c1403cc9..ec76ed82abb9 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -2350,6 +2350,8 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>>          struct mmc_blk_data *md;
>>          int devidx, ret;
>>          char cap_str[10];
>> +       bool cache_enabled = false;
>> +       bool fua_enabled = false;
>>
>>          devidx = ida_simple_get(&mmc_blk_ida, 0, max_devices, GFP_KERNEL);
>>          if (devidx < 0) {
>> @@ -2429,13 +2431,17 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>>                          md->flags |= MMC_BLK_CMD23;
>>          }
>>
>> -       if (mmc_card_mmc(card) &&
>> -           md->flags & MMC_BLK_CMD23 &&
>> +       if (md->flags & MMC_BLK_CMD23 &&
>>              ((card->ext_csd.rel_param & EXT_CSD_WR_REL_PARAM_EN) ||
>>               card->ext_csd.rel_sectors)) {
>>                  md->flags |= MMC_BLK_REL_WR;
>> -               blk_queue_write_cache(md->queue.queue, true, true);
>> +               fua_enabled = true;
>> +               cache_enabled = true;
>>          }
>> +       if (mmc_cache_enabled(card->host))
>> +               cache_enabled  = true;
>> +
>> +       blk_queue_write_cache(md->queue.queue, cache_enabled, fua_enabled);
>>
>>          string_get_size((u64)size, 512, STRING_UNITS_2,
>>                          cap_str, sizeof(cap_str));
>> --
>> 2.29.0
>>