Re: [PATCH v3 5/9] dma-buf: Move dma_buf_mmap_unlocked() to dynamic locking specification

[Christian König <christian.koenig@xxxxxxx>]

This should work, but I'm really wondering if this makes a difference 
for somebody.

Anyway the approach is fine with me: Acked-by: Christian König 
<christian.koenig@xxxxxxx>

Regards,
Christian.

Am 24.08.22 um 12:22 schrieb Dmitry Osipenko:
> Move dma_buf_mmap_unlocked() function to the dynamic locking specification
> by taking the reservation lock. Neither of the today's drivers take the
> reservation lock within the mmap() callback, hence it's safe to enforce
> the locking.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---
>   drivers/dma-buf/dma-buf.c | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index f358af401360..4556a12bd741 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -1348,6 +1348,8 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_end_cpu_access, DMA_BUF);
>   int dma_buf_mmap_unlocked(struct dma_buf *dmabuf, struct vm_area_struct *vma,
>   			  unsigned long pgoff)
>   {
> +	int ret;
> +
>   	if (WARN_ON(!dmabuf || !vma))
>   		return -EINVAL;
>   
> @@ -1368,7 +1370,11 @@ int dma_buf_mmap_unlocked(struct dma_buf *dmabuf, struct vm_area_struct *vma,
>   	vma_set_file(vma, dmabuf->file);
>   	vma->vm_pgoff = pgoff;
>   
> -	return dmabuf->ops->mmap(dmabuf, vma);
> +	dma_resv_lock(dmabuf->resv, NULL);
> +	ret = dmabuf->ops->mmap(dmabuf, vma);
> +	dma_resv_unlock(dmabuf->resv);
> +
> +	return ret;
>   }
>   EXPORT_SYMBOL_NS_GPL(dma_buf_mmap_unlocked, DMA_BUF);
>