linux-kernel - Re: [PATCH 0/3] sgi-gru: get_user

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Date:   Sun, 21 Jul 2019 21:49:48 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Bharath Vedartham <linux.bhar@...il.com>
Cc:     arnd@...db.de, sivanich@....com, gregkh@...uxfoundation.org,
        jhubbard@...dia.com, jglisse@...hat.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 0/3] sgi-gru: get_user_page changes

On Sun, Jul 21, 2019 at 09:28:02PM +0530, Bharath Vedartham wrote:
> This patch series incorporates a few changes in the get_user_page usage 
> of sgi-gru.
> 
> The main change is the first patch, which is a trivial one line change to 
> convert put_page to put_user_page to enable tracking of get_user_pages.
> 
> The second patch removes an uneccessary ifdef of CONFIG_HUGETLB.
> 
> The third patch adds __get_user_pages_fast in atomic_pte_lookup to retrive
> a physical user page in an atomic context instead of manually walking up
> the page tables like the current code does. This patch should be subject to 
> more review from the gup people.
> 
> drivers/misc/sgi-gru/* builds after this patch series. But I do not have the 
> hardware to verify these changes. 
> 
> The first patch implements gup tracking in the current code. This is to be tested
> as to check whether gup tracking works properly. Currently, in the upstream kernels
> put_user_page simply calls put_page. But that is to change in the future. 
> Any suggestions as to how to test this code?
> 
> The implementation of gup tracking is in:
> https://github.com/johnhubbard/linux/tree/gup_dma_core
> 
> We could test it by applying the first patch to the above tree and test it.
> 
> More details are in the individual changelogs.
> 
> Bharath Vedartham (3):

I don't have an opinion on the second patch regarding any performance concerns
since I'm not familiar with this hardware.

But from a GUP POV For the series.

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

>   sgi-gru: Convert put_page() to get_user_page*()
>   sgi-gru: Remove CONFIG_HUGETLB_PAGE ifdef
>   sgi-gru: Use __get_user_pages_fast in atomic_pte_lookup
> 
>  drivers/misc/sgi-gru/grufault.c | 50 +++++++----------------------------------
>  1 file changed, 8 insertions(+), 42 deletions(-)
> 
> -- 
> 2.7.4
>