Re: [PATCH 3/3] dma-mapping: remove dma_zalloc_coherent()

From: Julia Lawall
Date: Tue Jan 08 2019 - 09:29:50 EST




On Tue, 8 Jan 2019, Christoph Hellwig wrote:

> From: Luis Chamberlain <mcgrof@xxxxxxxxxx>
>
> dma_zalloc_coherent() is no longer needed as it has no users because
> dma_alloc_coherent() already zeroes out memory for us.
>
> The Coccinelle grammar rule that used to check for dma_alloc_coherent()
> + memset() is modified so that it just tells the user that the memset is
> not needed anymore.
>
> Suggested-by: Christoph Hellwig <hch@xxxxxx>
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> include/linux/dma-mapping.h | 9 ---------
> scripts/coccinelle/api/alloc/alloc_cast.cocci | 8 ++++----
> scripts/coccinelle/api/alloc/zalloc-simple.cocci | 11 +----------
> 3 files changed, 5 insertions(+), 23 deletions(-)
>
> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
> index cef2127e1d70..f6ded992c183 100644
> --- a/include/linux/dma-mapping.h
> +++ b/include/linux/dma-mapping.h
> @@ -717,15 +717,6 @@ static inline unsigned long dma_max_pfn(struct device *dev)
> }
> #endif
>
> -/*
> - * Please always use dma_alloc_coherent instead as it already zeroes the memory!
> - */
> -static inline void *dma_zalloc_coherent(struct device *dev, size_t size,
> - dma_addr_t *dma_handle, gfp_t flag)
> -{
> - return dma_alloc_coherent(dev, size, dma_handle, flag);
> -}
> -
> static inline int dma_get_cache_alignment(void)
> {
> #ifdef ARCH_DMA_MINALIGN
> diff --git a/scripts/coccinelle/api/alloc/alloc_cast.cocci b/scripts/coccinelle/api/alloc/alloc_cast.cocci
> index 408ee3879f9b..18fedf7c60ed 100644
> --- a/scripts/coccinelle/api/alloc/alloc_cast.cocci
> +++ b/scripts/coccinelle/api/alloc/alloc_cast.cocci
> @@ -32,7 +32,7 @@ type T;
> (T *)
> \(kmalloc\|kzalloc\|kcalloc\|kmem_cache_alloc\|kmem_cache_zalloc\|
> kmem_cache_alloc_node\|kmalloc_node\|kzalloc_node\|vmalloc\|vzalloc\|
> - dma_alloc_coherent\|dma_zalloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> + dma_alloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> kvmalloc\|kvzalloc\|kvmalloc_node\|kvzalloc_node\|pci_alloc_consistent\|
> pci_zalloc_consistent\|kmem_alloc\|kmem_zalloc\|kmem_zone_alloc\|
> kmem_zone_zalloc\|vmalloc_node\|vzalloc_node\)(...)
> @@ -55,7 +55,7 @@ type r1.T;
> * (T *)
> \(kmalloc\|kzalloc\|kcalloc\|kmem_cache_alloc\|kmem_cache_zalloc\|
> kmem_cache_alloc_node\|kmalloc_node\|kzalloc_node\|vmalloc\|vzalloc\|
> - dma_alloc_coherent\|dma_zalloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> + dma_alloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> kvmalloc\|kvzalloc\|kvmalloc_node\|kvzalloc_node\|pci_alloc_consistent\|
> pci_zalloc_consistent\|kmem_alloc\|kmem_zalloc\|kmem_zone_alloc\|
> kmem_zone_zalloc\|vmalloc_node\|vzalloc_node\)(...)
> @@ -78,7 +78,7 @@ type r1.T;
> - (T *)
> \(kmalloc\|kzalloc\|kcalloc\|kmem_cache_alloc\|kmem_cache_zalloc\|
> kmem_cache_alloc_node\|kmalloc_node\|kzalloc_node\|vmalloc\|vzalloc\|
> - dma_alloc_coherent\|dma_zalloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> + dma_alloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> kvmalloc\|kvzalloc\|kvmalloc_node\|kvzalloc_node\|pci_alloc_consistent\|
> pci_zalloc_consistent\|kmem_alloc\|kmem_zalloc\|kmem_zone_alloc\|
> kmem_zone_zalloc\|vmalloc_node\|vzalloc_node\)(...)
> @@ -95,7 +95,7 @@ position p;
> (T@p *)
> \(kmalloc\|kzalloc\|kcalloc\|kmem_cache_alloc\|kmem_cache_zalloc\|
> kmem_cache_alloc_node\|kmalloc_node\|kzalloc_node\|vmalloc\|vzalloc\|
> - dma_alloc_coherent\|dma_zalloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> + dma_alloc_coherent\|devm_kmalloc\|devm_kzalloc\|
> kvmalloc\|kvzalloc\|kvmalloc_node\|kvzalloc_node\|pci_alloc_consistent\|
> pci_zalloc_consistent\|kmem_alloc\|kmem_zalloc\|kmem_zone_alloc\|
> kmem_zone_zalloc\|vmalloc_node\|vzalloc_node\)(...)
> diff --git a/scripts/coccinelle/api/alloc/zalloc-simple.cocci b/scripts/coccinelle/api/alloc/zalloc-simple.cocci
> index d819275b7fde..5cd1991c582e 100644
> --- a/scripts/coccinelle/api/alloc/zalloc-simple.cocci
> +++ b/scripts/coccinelle/api/alloc/zalloc-simple.cocci
> @@ -69,15 +69,6 @@ statement S;
> - x = (T)vmalloc(E1);
> + x = (T)vzalloc(E1);
> |
> -- x = dma_alloc_coherent(E2,E1,E3,E4);
> -+ x = dma_zalloc_coherent(E2,E1,E3,E4);
> -|
> -- x = (T *)dma_alloc_coherent(E2,E1,E3,E4);
> -+ x = dma_zalloc_coherent(E2,E1,E3,E4);
> -|
> -- x = (T)dma_alloc_coherent(E2,E1,E3,E4);
> -+ x = (T)dma_zalloc_coherent(E2,E1,E3,E4);

Perhaps it would be better to make a separate rule that removed the
memset? It wouldn't need the three cases.
x = (T)dma_alloc_coherent(E2,E1,E3,E4); would take care of everything.

julia

> -|
> - x = kmalloc_node(E1,E2,E3);
> + x = kzalloc_node(E1,E2,E3);
> |
> @@ -225,7 +216,7 @@ p << r2.p;
> x << r2.x;
> @@
>
> -msg="WARNING: dma_zalloc_coherent should be used for %s, instead of dma_alloc_coherent/memset" % (x)
> +msg="WARNING: dma_alloc_coherent use in %s already zeroes out memory, so memset is not needed" % (x)
> coccilib.report.print_report(p[0], msg)
>
> //-----------------------------------------------------------------
> --
> 2.20.1
>
>