On Wed, Jul 5, 2017 at 9:00 PM, Christoph Hellwig [off-list ref] wrote:

On Thu, May 18, 2017 at 11:36:14AM +0200, Christoph Hellwig wrote:

quoted

On Thu, May 18, 2017 at 11:29:34AM +0200, Linus Walleij wrote:

quoted

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?

Sorry, just back from vacation.

I am rebasing my MMC patch stack, so I will take this opportunity to
also look at this during the week. I just need to make sure I find the
right userspace calls to exercise it.

Yours,
Linus Walleij