linux-kernel - Re: [PATCH] staging: gasket: Convert get_user_pages*() --> pin_user

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Message-ID: <20200529074516.GL30374@kadam>
Date:   Fri, 29 May 2020 10:45:16 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Souptick Joarder <jrdr.linux@...il.com>,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Rob Springer <rspringer@...gle.com>,
        Todd Poynor <toddpoynor@...gle.com>
Subject: Re: [PATCH] staging: gasket: Convert get_user_pages*() -->
 pin_user_pages*()

On Fri, May 29, 2020 at 12:38:20AM -0700, John Hubbard wrote:
> On 2020-05-28 23:27, Souptick Joarder wrote:
> > On Fri, May 29, 2020 at 11:46 AM Souptick Joarder <jrdr.linux@...il.com> wrote:
> > > 
> > > On Thu, May 28, 2020 at 4:34 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > > > 
> > > > On Thu, May 28, 2020 at 02:32:42AM +0530, Souptick Joarder wrote:
> > > > > This code was using get_user_pages_fast(), in a "Case 2" scenario
> > > > > (DMA/RDMA), using the categorization from [1]. That means that it's
> > > > > time to convert the get_user_pages_fast() + put_page() calls to
> > > > > pin_user_pages_fast() + unpin_user_page() calls.
> > > > 
> > > > You are saying that the page is used for DIO and not DMA, but it sure
> > > > looks to me like it is used for DMA.
> > > 
> > > No, I was referring to "Case 2" scenario in change log which means  it is
> > > used for DMA, not DIO.
> 
> Hi,
> 
> Dan, I also uncertain as to how you read this as referring to DIO. Case 2 is
> DMA or RDMA, and in fact the proposed commit log says both of those things:
> Case 2 and DMA/RDMA. I don't see "DIO" anywhere here...

I thought he meant that the original code was appropriate for DMA and he
was fixing it.  :P

regards,
dan carpenter