linux-kernel - Re: [PATCH v3] dma-buf: system_heap: Use 'for_each_sgtable

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Date:   Fri, 26 Nov 2021 07:31:00 +0100
From:   Greg KH <greg@...ah.com>
To:     guangming.cao@...iatek.com
Cc:     robin.murphy@....com, Brian.Starkey@....com,
        benjamin.gaignard@...aro.org, christian.koenig@....com,
        dri-devel@...ts.freedesktop.org, john.stultz@...aro.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,
        sumit.semwal@...aro.org, wsd_upstream@...iatek.com,
        stable@...r.kernel.org
Subject: Re: [PATCH v3] dma-buf: system_heap: Use 'for_each_sgtable_sg' in
 pages free flow

On Fri, Nov 26, 2021 at 11:16:05AM +0800, 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.
> 
> Fixes: d963ab0f15fb0 ("dma-buf: system_heap: Allocate higher order pages if available")
> 
> Signed-off-by: Guangming <Guangming.Cao@...iatek.com>
> ---
>  drivers/dma-buf/heaps/system_heap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index 23a7e74ef966..8660508f3684 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -289,7 +289,7 @@ static void system_heap_dma_buf_release(struct dma_buf *dmabuf)
>  	int i;
>  
>  	table = &buffer->sg_table;
> -	for_each_sg(table->sgl, sg, table->nents, i) {
> +	for_each_sgtable_sg(table, sg, i) {
>  		struct page *page = sg_page(sg);
>  
>  		__free_pages(page, compound_order(page));
> -- 
> 2.17.1
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>