linux-kernel - RE: [PATCH v3 1/2] mmc: block: Issue flush only if allowed

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Message-ID: <DM6PR04MB6575DE38D3B919171549A1D0FC489@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Tue, 20 Apr 2021 13:22:52 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brendan Peter <bpeter@...x.com>
Subject: RE: [PATCH v3 1/2] mmc: block: Issue flush only if allowed

 
> On 20/04/21 8:53 am, Avri Altman wrote:
> > The cache may be flushed to the nonvolatile storage by writing to
> > FLUSH_CACHE byte (EXT_CSD byte [32]). When in command queueing mode,
> the
> > cache may be flushed by issuing a CMDQ_TASK_ DEV_MGMT (CMD48) with a
> > FLUSH_CACHE op-code.  Either way, verify that The cache function is
> > turned ON before doing so.
> >
> > fixes: 1e8e55b67030 (mmc: block: Add CQE support)
> >
> > Reported-by: Brendan Peter <bpeter@...x.com>
> > Tested-by: Brendan Peter <bpeter@...x.com>
> > Signed-off-by: Avri Altman <avri.altman@....com>
> > ---
> >  drivers/mmc/core/block.c   | 7 +++++++
> >  drivers/mmc/core/mmc.c     | 2 +-
> >  drivers/mmc/core/mmc_ops.h | 5 +++++
> >  3 files changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> > index 8bfd4d95b386..5b6501fc9fb7 100644
> > --- a/drivers/mmc/core/block.c
> > +++ b/drivers/mmc/core/block.c
> > @@ -1476,6 +1476,11 @@ static int mmc_blk_cqe_issue_flush(struct
> mmc_queue *mq, struct request *req)
> >       struct mmc_queue_req *mqrq = req_to_mmc_queue_req(req);
> >       struct mmc_request *mrq = mmc_blk_cqe_prep_dcmd(mqrq, req);
> >
> > +     if (mmc_card_mmc(mq->card) && !mmc_flush_allowed(mq->card)) {
> > +             blk_mq_end_request(req, BLK_STS_OK);
> > +             return -EPERM;
> > +     }
> > +
> >       mrq->cmd->opcode = MMC_SWITCH;
> >       mrq->cmd->arg = (MMC_SWITCH_MODE_WRITE_BYTE << 24) |
> >                       (EXT_CSD_FLUSH_CACHE << 16) |
> > @@ -2226,6 +2231,8 @@ enum mmc_issued mmc_blk_mq_issue_rq(struct
> mmc_queue *mq, struct request *req)
> >               switch (req_op(req)) {
> >               case REQ_OP_FLUSH:
> >                       ret = mmc_blk_cqe_issue_flush(mq, req);
> > +                     if (ret == -EPERM)
> > +                             return MMC_REQ_FINISHED;
> 
> Using an error code for this case seems a little fragile.
> 
> How about something like:
> 
>                 case REQ_OP_FLUSH:
>                         if (mmc_blk_cache_disabled(mq->card)) {
>                                 blk_mq_end_request(req, BLK_STS_OK);
>                                 return MMC_REQ_FINISHED;
>                         }
>                         ret = mmc_blk_cqe_issue_flush(mq, req);
> 
> 
> static bool mmc_blk_cache_disabled(struct mmc_card *card)
> {
>         return mmc_card_mmc(mq->card) && !mmc_flush_allowed(card);
> }
Done.

Thanks,
Avri