From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 4/6 v2] mmc: block: move single ioctl() commands to
        block requests
Date: Wed, 5 Jul 2017 21:00:16 +0200
Message-ID: <20170705190016.GA7008@lst.de>
References: <20170518092936.9277-1-linus.walleij@linaro.org> <20170518092936.9277-4-linus.walleij@linaro.org> <20170518093614.GB9250@lst.de>
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To: Linus Walleij <linus.walleij@linaro.org>
Cc: linux-mmc@vger.kernel.org, Ulf Hansson <ulf.hansson@linaro.org>, Adrian Hunter <adrian.hunter@intel.com>, linux-block@vger.kernel.org, Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>, Arnd Bergmann <arnd@arndb.de>, Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>, Paolo Valente <paolo.valente@linaro.org>
List-Id: linux-mmc@vger.kernel.org

Hi Linus,

On Thu, May 18, 2017 at 11:36:14AM +0200, Christoph Hellwig wrote:
> On Thu, May 18, 2017 at 11:29:34AM +0200, Linus Walleij wrote:
> > We are storing the ioctl() in/out argument as a pointer in
> > the per-request struct mmc_blk_request container.
> 
> Btw, for the main ioctl data (not the little reponse field) it might
> make sense to use blk_rq_map_user, which will do a get_user_pages
> on the user data if the alignment fits, and otherwise handle the
> kernel bounce buffering for you.  This should simplify the code
> quite a bit more, and in the case where you can access the user
> memory directly provide a nice little performance boost.

Did you get a chance to look into this?