linux-kernel - Re: [PATCH v4] dma-buf: system_heap: Use 'for_each_sgtable

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Message-ID: <CAO_48GHxanR=-mN232ANwxQEiBo9zb3WjvO-6WmP6eFYWA1M5A@mail.gmail.com>
Date:   Wed, 1 Dec 2021 15:39:17 +0530
From:   Sumit Semwal <sumit.semwal@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     guangming.cao@...iatek.com, greg@...ah.com, brian.starkey@....com,
        benjamin.gaignard@...aro.org, christian.koenig@....com,
        dri-devel@...ts.freedesktop.org, labbott@...hat.com,
        linaro-mm-sig@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        lmark@...eaurora.org, matthias.bgg@...il.com, robin.murphy@....com,
        stable@...r.kernel.org, wsd_upstream@...iatek.com,
        kuan-ying.lee@...iatek.com
Subject: Re: [PATCH v4] dma-buf: system_heap: Use 'for_each_sgtable_sg' in
 pages free flow

Hello Guangming,

On Mon, 29 Nov 2021 at 23:35, John Stultz <john.stultz@...aro.org> wrote:
>
> On Thu, Nov 25, 2021 at 11:48 PM <guangming.cao@...iatek.com> wrote:
> >
> > From: Guangming <Guangming.Cao@...iatek.com>
> >
> > For previous version, it uses 'sg_table.nent's to traverse sg_table in pages
> > free flow.
> > However, 'sg_table.nents' is reassigned in 'dma_map_sg', it means the number of
> > created entries in the DMA adderess space.
> > So, use 'sg_table.nents' in pages free flow will case some pages can't be freed.
> >
> > Here we should use sg_table.orig_nents to free pages memory, but use the
> > sgtable helper 'for each_sgtable_sg'(, instead of the previous rather common
> > helper 'for_each_sg' which maybe cause memory leak) is much better.

Thanks for catching this and the patch; applied to drm-misc-fixes.
> >
> > Fixes: d963ab0f15fb0 ("dma-buf: system_heap: Allocate higher order pages if available")
> > Signed-off-by: Guangming <Guangming.Cao@...iatek.com>
> > Reviewed-by: Robin Murphy <robin.murphy@....com>
> > Cc: <stable@...r.kernel.org> # 5.11.*
>
> Thanks so much for catching this and sending in all the revisions!
>
> Reviewed-by: John Stultz <john.stultz@...aro.org>


Best,
Sumit.

-- 
Thanks and regards,

Sumit Semwal (he / him)
Tech Lead - LCG, Vertical Technologies
Linaro.org │ Open source software for ARM SoCs