[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Marek Szyprowski]

cma_alloc() function doesn't really support gfp flags other than
__GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.

This will help to avoid giving false feeling that this function supports
standard gfp flags and callers can pass __GFP_ZERO to get zeroed buffer,
what has already been an issue: see commit dd65a941f6ba ("arm64:
dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag").

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 arch/powerpc/kvm/book3s_hv_builtin.c       | 2 +-
 drivers/s390/char/vmcp.c                   | 2 +-
 drivers/staging/android/ion/ion_cma_heap.c | 2 +-
 include/linux/cma.h                        | 2 +-
 kernel/dma/contiguous.c                    | 3 ++-
 mm/cma.c                                   | 8 ++++----
 mm/cma_debug.c                             | 2 +-
 7 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
index d4a3f4da409b..fc6bb9630a9c 100644
--- a/arch/powerpc/kvm/book3s_hv_builtin.c
+++ b/arch/powerpc/kvm/book3s_hv_builtin.c
@@ -77,7 +77,7 @@ struct page *kvm_alloc_hpt_cma(unsigned long nr_pages)
 	VM_BUG_ON(order_base_2(nr_pages) < KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);
 
 	return cma_alloc(kvm_cma, nr_pages, order_base_2(HPT_ALIGN_PAGES),
-			 GFP_KERNEL);
+			 false);
 }
 EXPORT_SYMBOL_GPL(kvm_alloc_hpt_cma);
 
diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
index 948ce82a7725..0fa1b6b1491a 100644
--- a/drivers/s390/char/vmcp.c
+++ b/drivers/s390/char/vmcp.c
@@ -68,7 +68,7 @@ static void vmcp_response_alloc(struct vmcp_session *session)
 	 * anymore the system won't work anyway.
 	 */
 	if (order > 2)
-		page = cma_alloc(vmcp_cma, nr_pages, 0, GFP_KERNEL);
+		page = cma_alloc(vmcp_cma, nr_pages, 0, false);
 	if (page) {
 		session->response = (char *)page_to_phys(page);
 		session->cma_alloc = 1;
diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c
index 49718c96bf9e..3fafd013d80a 100644
--- a/drivers/staging/android/ion/ion_cma_heap.c
+++ b/drivers/staging/android/ion/ion_cma_heap.c
@@ -39,7 +39,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
 	if (align > CONFIG_CMA_ALIGNMENT)
 		align = CONFIG_CMA_ALIGNMENT;
 
-	pages = cma_alloc(cma_heap->cma, nr_pages, align, GFP_KERNEL);
+	pages = cma_alloc(cma_heap->cma, nr_pages, align, false);
 	if (!pages)
 		return -ENOMEM;
 
diff --git a/include/linux/cma.h b/include/linux/cma.h
index bf90f0bb42bd..190184b5ff32 100644
--- a/include/linux/cma.h
+++ b/include/linux/cma.h
@@ -33,7 +33,7 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
 					const char *name,
 					struct cma **res_cma);
 extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
-			      gfp_t gfp_mask);
+			      bool no_warn);
 extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
 
 extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index d987dcd1bd56..19ea5d70150c 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -191,7 +191,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
 	if (align > CONFIG_CMA_ALIGNMENT)
 		align = CONFIG_CMA_ALIGNMENT;
 
-	return cma_alloc(dev_get_cma_area(dev), count, align, gfp_mask);
+	return cma_alloc(dev_get_cma_area(dev), count, align,
+			 gfp_mask & __GFP_NOWARN);
 }
 
 /**
diff --git a/mm/cma.c b/mm/cma.c
index 5809bbe360d7..4cb76121a3ab 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -395,13 +395,13 @@ static inline void cma_debug_show_areas(struct cma *cma) { }
  * @cma:   Contiguous memory region for which the allocation is performed.
  * @count: Requested number of pages.
  * @align: Requested alignment of pages (in PAGE_SIZE order).
- * @gfp_mask:  GFP mask to use during compaction
+ * @no_warn: Avoid printing message about failed allocation
  *
  * This function allocates part of contiguous memory on specific
  * contiguous memory area.
  */
 struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
-		       gfp_t gfp_mask)
+		       bool no_warn)
 {
 	unsigned long mask, offset;
 	unsigned long pfn = -1;
@@ -447,7 +447,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 		pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit);
 		mutex_lock(&cma_mutex);
 		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA,
-					 gfp_mask);
+				     GFP_KERNEL | (no_warn ? __GFP_NOWARN : 0));
 		mutex_unlock(&cma_mutex);
 		if (ret == 0) {
 			page = pfn_to_page(pfn);
@@ -466,7 +466,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 
 	trace_cma_alloc(pfn, page, count, align);
 
-	if (ret && !(gfp_mask & __GFP_NOWARN)) {
+	if (ret && !no_warn) {
 		pr_err("%s: alloc failed, req-size: %zu pages, ret: %d\n",
 			__func__, count, ret);
 		cma_debug_show_areas(cma);
diff --git a/mm/cma_debug.c b/mm/cma_debug.c
index f23467291cfb..ad6723e9d110 100644
--- a/mm/cma_debug.c
+++ b/mm/cma_debug.c
@@ -139,7 +139,7 @@ static int cma_alloc_mem(struct cma *cma, int count)
 	if (!mem)
 		return -ENOMEM;
 
-	p = cma_alloc(cma, count, 0, GFP_KERNEL);
+	p = cma_alloc(cma, count, 0, false);
 	if (!p) {
 		kfree(mem);
 		return -ENOMEM;
-- 
2.17.1

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Michal Hocko]

On Mon 09-07-18 14:19:55, Marek Szyprowski wrote:
> cma_alloc() function doesn't really support gfp flags other than
> __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
> 
> This will help to avoid giving false feeling that this function supports
> standard gfp flags and callers can pass __GFP_ZERO to get zeroed buffer,
> what has already been an issue: see commit dd65a941f6ba ("arm64:
> dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag").
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

Thanks! This makes perfect sense to me. If there is a real need for the
gfp_mask then we should start by defining the semantic first.

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  arch/powerpc/kvm/book3s_hv_builtin.c       | 2 +-
>  drivers/s390/char/vmcp.c                   | 2 +-
>  drivers/staging/android/ion/ion_cma_heap.c | 2 +-
>  include/linux/cma.h                        | 2 +-
>  kernel/dma/contiguous.c                    | 3 ++-
>  mm/cma.c                                   | 8 ++++----
>  mm/cma_debug.c                             | 2 +-
>  7 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
> index d4a3f4da409b..fc6bb9630a9c 100644
> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
> @@ -77,7 +77,7 @@ struct page *kvm_alloc_hpt_cma(unsigned long nr_pages)
>  	VM_BUG_ON(order_base_2(nr_pages) < KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);
>  
>  	return cma_alloc(kvm_cma, nr_pages, order_base_2(HPT_ALIGN_PAGES),
> -			 GFP_KERNEL);
> +			 false);
>  }
>  EXPORT_SYMBOL_GPL(kvm_alloc_hpt_cma);
>  
> diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
> index 948ce82a7725..0fa1b6b1491a 100644
> --- a/drivers/s390/char/vmcp.c
> +++ b/drivers/s390/char/vmcp.c
> @@ -68,7 +68,7 @@ static void vmcp_response_alloc(struct vmcp_session *session)
>  	 * anymore the system won't work anyway.
>  	 */
>  	if (order > 2)
> -		page = cma_alloc(vmcp_cma, nr_pages, 0, GFP_KERNEL);
> +		page = cma_alloc(vmcp_cma, nr_pages, 0, false);
>  	if (page) {
>  		session->response = (char *)page_to_phys(page);
>  		session->cma_alloc = 1;
> diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c
> index 49718c96bf9e..3fafd013d80a 100644
> --- a/drivers/staging/android/ion/ion_cma_heap.c
> +++ b/drivers/staging/android/ion/ion_cma_heap.c
> @@ -39,7 +39,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
>  	if (align > CONFIG_CMA_ALIGNMENT)
>  		align = CONFIG_CMA_ALIGNMENT;
>  
> -	pages = cma_alloc(cma_heap->cma, nr_pages, align, GFP_KERNEL);
> +	pages = cma_alloc(cma_heap->cma, nr_pages, align, false);
>  	if (!pages)
>  		return -ENOMEM;
>  
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> index bf90f0bb42bd..190184b5ff32 100644
> --- a/include/linux/cma.h
> +++ b/include/linux/cma.h
> @@ -33,7 +33,7 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
>  					const char *name,
>  					struct cma **res_cma);
>  extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
> -			      gfp_t gfp_mask);
> +			      bool no_warn);
>  extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
>  
>  extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> index d987dcd1bd56..19ea5d70150c 100644
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -191,7 +191,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
>  	if (align > CONFIG_CMA_ALIGNMENT)
>  		align = CONFIG_CMA_ALIGNMENT;
>  
> -	return cma_alloc(dev_get_cma_area(dev), count, align, gfp_mask);
> +	return cma_alloc(dev_get_cma_area(dev), count, align,
> +			 gfp_mask & __GFP_NOWARN);
>  }
>  
>  /**
> diff --git a/mm/cma.c b/mm/cma.c
> index 5809bbe360d7..4cb76121a3ab 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -395,13 +395,13 @@ static inline void cma_debug_show_areas(struct cma *cma) { }
>   * @cma:   Contiguous memory region for which the allocation is performed.
>   * @count: Requested number of pages.
>   * @align: Requested alignment of pages (in PAGE_SIZE order).
> - * @gfp_mask:  GFP mask to use during compaction
> + * @no_warn: Avoid printing message about failed allocation
>   *
>   * This function allocates part of contiguous memory on specific
>   * contiguous memory area.
>   */
>  struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
> -		       gfp_t gfp_mask)
> +		       bool no_warn)
>  {
>  	unsigned long mask, offset;
>  	unsigned long pfn = -1;
> @@ -447,7 +447,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
>  		pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit);
>  		mutex_lock(&cma_mutex);
>  		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA,
> -					 gfp_mask);
> +				     GFP_KERNEL | (no_warn ? __GFP_NOWARN : 0));
>  		mutex_unlock(&cma_mutex);
>  		if (ret == 0) {
>  			page = pfn_to_page(pfn);
> @@ -466,7 +466,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
>  
>  	trace_cma_alloc(pfn, page, count, align)>  
> -	if (ret && !(gfp_mask & __GFP_NOWARN)) {
> +	if (ret && !no_warn) {
>  		pr_err("%s: alloc failed, req-size: %zu pages, ret: %d\n",
>  			__func__, count, ret);
>  		cma_debug_show_areas(cma);
> diff --git a/mm/cma_debug.c b/mm/cma_debug.c
> index f23467291cfb..ad6723e9d110 100644
> --- a/mm/cma_debug.c
> +++ b/mm/cma_debug.c
> @@ -139,7 +139,7 @@ static int cma_alloc_mem(struct cma *cma, int count)
>  	if (!mem)
>  		return -ENOMEM;
>  
> -	p = cma_alloc(cma, count, 0, GFP_KERNEL);
> +	p = cma_alloc(cma, count, 0, false);
>  	if (!p) {
>  		kfree(mem);
>  		return -ENOMEM;
> -- 
> 2.17.1
> 

-- 
Michal Hocko
SUSE Labs

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Laura Abbott]

On 07/09/2018 05:19 AM, Marek Szyprowski wrote:
> cma_alloc() function doesn't really support gfp flags other than
> __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
> 
> This will help to avoid giving false feeling that this function supports
> standard gfp flags and callers can pass __GFP_ZERO to get zeroed buffer,
> what has already been an issue: see commit dd65a941f6ba ("arm64:
> dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag").
> 

For Ion,

Acked-by: Laura Abbott <labbott@redhat.com>

> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
>   arch/powerpc/kvm/book3s_hv_builtin.c       | 2 +-
>   drivers/s390/char/vmcp.c                   | 2 +-
>   drivers/staging/android/ion/ion_cma_heap.c | 2 +-
>   include/linux/cma.h                        | 2 +-
>   kernel/dma/contiguous.c                    | 3 ++-
>   mm/cma.c                                   | 8 ++++----
>   mm/cma_debug.c                             | 2 +-
>   7 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
> index d4a3f4da409b..fc6bb9630a9c 100644
> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
> @@ -77,7 +77,7 @@ struct page *kvm_alloc_hpt_cma(unsigned long nr_pages)
>   	VM_BUG_ON(order_base_2(nr_pages) < KVM_CMA_CHUNK_ORDER - PAGE_SHIFT);
>   
>   	return cma_alloc(kvm_cma, nr_pages, order_base_2(HPT_ALIGN_PAGES),
> -			 GFP_KERNEL);
> +			 false);
>   }
>   EXPORT_SYMBOL_GPL(kvm_alloc_hpt_cma);
>   
> diff --git a/drivers/s390/char/vmcp.c b/drivers/s390/char/vmcp.c
> index 948ce82a7725..0fa1b6b1491a 100644
> --- a/drivers/s390/char/vmcp.c
> +++ b/drivers/s390/char/vmcp.c
> @@ -68,7 +68,7 @@ static void vmcp_response_alloc(struct vmcp_session *session)
>   	 * anymore the system won't work anyway.
>   	 */
>   	if (order > 2)
> -		page = cma_alloc(vmcp_cma, nr_pages, 0, GFP_KERNEL);
> +		page = cma_alloc(vmcp_cma, nr_pages, 0, false);
>   	if (page) {
>   		session->response = (char *)page_to_phys(page);
>   		session->cma_alloc = 1;
> diff --git a/drivers/staging/android/ion/ion_cma_heap.c b/drivers/staging/android/ion/ion_cma_heap.c
> index 49718c96bf9e..3fafd013d80a 100644
> --- a/drivers/staging/android/ion/ion_cma_heap.c
> +++ b/drivers/staging/android/ion/ion_cma_heap.c
> @@ -39,7 +39,7 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,
>   	if (align > CONFIG_CMA_ALIGNMENT)
>   		align = CONFIG_CMA_ALIGNMENT;
>   
> -	pages = cma_alloc(cma_heap->cma, nr_pages, align, GFP_KERNEL);
> +	pages = cma_alloc(cma_heap->cma, nr_pages, align, false);
>   	if (!pages)
>   		return -ENOMEM;
>   
> diff --git a/include/linux/cma.h b/include/linux/cma.h
> index bf90f0bb42bd..190184b5ff32 100644
> --- a/include/linux/cma.h
> +++ b/include/linux/cma.h
> @@ -33,7 +33,7 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
>   					const char *name,
>   					struct cma **res_cma);
>   extern struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
> -			      gfp_t gfp_mask);
> +			      bool no_warn);
>   extern bool cma_release(struct cma *cma, const struct page *pages, unsigned int count);
>   
>   extern int cma_for_each_area(int (*it)(struct cma *cma, void *data), void *data);
> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> index d987dcd1bd56..19ea5d70150c 100644
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -191,7 +191,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
>   	if (align > CONFIG_CMA_ALIGNMENT)
>   		align = CONFIG_CMA_ALIGNMENT;
>   
> -	return cma_alloc(dev_get_cma_area(dev), count, align, gfp_mask);
> +	return cma_alloc(dev_get_cma_area(dev), count, align,
> +			 gfp_mask & __GFP_NOWARN);
>   }
>   
>   /**
> diff --git a/mm/cma.c b/mm/cma.c
> index 5809bbe360d7..4cb76121a3ab 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -395,13 +395,13 @@ static inline void cma_debug_show_areas(struct cma *cma) { }
>    * @cma:   Contiguous memory region for which the allocation is performed.
>    * @count: Requested number of pages.
>    * @align: Requested alignment of pages (in PAGE_SIZE order).
> - * @gfp_mask:  GFP mask to use during compaction
> + * @no_warn: Avoid printing message about failed allocation
>    *
>    * This function allocates part of contiguous memory on specific
>    * contiguous memory area.
>    */
>   struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
> -		       gfp_t gfp_mask)
> +		       bool no_warn)
>   {
>   	unsigned long mask, offset;
>   	unsigned long pfn = -1;
> @@ -447,7 +447,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
>   		pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit);
>   		mutex_lock(&cma_mutex);
>   		ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA,
> -					 gfp_mask);
> +				     GFP_KERNEL | (no_warn ? __GFP_NOWARN : 0));
>   		mutex_unlock(&cma_mutex);
>   		if (ret == 0) {
>   			page = pfn_to_page(pfn);
> @@ -466,7 +466,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
>   
>   	trace_cma_alloc(pfn, page, count, align);
>   
> -	if (ret && !(gfp_mask & __GFP_NOWARN)) {
> +	if (ret && !no_warn) {
>   		pr_err("%s: alloc failed, req-size: %zu pages, ret: %d\n",
>   			__func__, count, ret);
>   		cma_debug_show_areas(cma);
> diff --git a/mm/cma_debug.c b/mm/cma_debug.c
> index f23467291cfb..ad6723e9d110 100644
> --- a/mm/cma_debug.c
> +++ b/mm/cma_debug.c
> @@ -139,7 +139,7 @@ static int cma_alloc_mem(struct cma *cma, int count)
>   	if (!mem)
>   		return -ENOMEM;
>   
> -	p = cma_alloc(cma, count, 0, GFP_KERNEL);
> +	p = cma_alloc(cma, count, 0, false);
>   	if (!p) {
>   		kfree(mem);
>   		return -ENOMEM;
> 

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Joonsoo Kim]

Hello, Marek.

2018-07-09 21:19 GMT+09:00 Marek Szyprowski <m.szyprowski@samsung.com>:
> cma_alloc() function doesn't really support gfp flags other than
> __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.

Although gfp_mask isn't used in cma_alloc() except no_warn, it can be used
in alloc_contig_range(). For example, if passed gfp mask has no __GFP_FS,
compaction(isolation) would work differently. Do you have considered
such a case?

Thanks.

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Michal Hocko]

On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
> Hello, Marek.
> 
> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <m.szyprowski@samsung.com>:
> > cma_alloc() function doesn't really support gfp flags other than
> > __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
> 
> Although gfp_mask isn't used in cma_alloc() except no_warn, it can be used
> in alloc_contig_range(). For example, if passed gfp mask has no __GFP_FS,
> compaction(isolation) would work differently. Do you have considered
> such a case?

Does any of cma_alloc users actually care about GFP_NO{FS,IO}?
-- 
Michal Hocko
SUSE Labs

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Joonsoo Kim]

2018-07-10 18:50 GMT+09:00 Michal Hocko <mhocko@kernel.org>:
> On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
>> Hello, Marek.
>>
>> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <m.szyprowski@samsung.com>:
>> > cma_alloc() function doesn't really support gfp flags other than
>> > __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
>>
>> Although gfp_mask isn't used in cma_alloc() except no_warn, it can be used
>> in alloc_contig_range(). For example, if passed gfp mask has no __GFP_FS,
>> compaction(isolation) would work differently. Do you have considered
>> such a case?
>
> Does any of cma_alloc users actually care about GFP_NO{FS,IO}?

I don't know. My guess is that cma_alloc() is used for DMA allocation so
block device would use it, too. If fs/block subsystem initiates the
request for the device,
it would be possible that cma_alloc() is called with such a flag.
Again, I don't know
much about those subsystem so I would be wrong.

Thanks.

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Michal Hocko]

On Wed 11-07-18 16:35:28, Joonsoo Kim wrote:
> 2018-07-10 18:50 GMT+09:00 Michal Hocko <mhocko@kernel.org>:
> > On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
> >> Hello, Marek.
> >>
> >> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <m.szyprowski@samsung.com>:
> >> > cma_alloc() function doesn't really support gfp flags other than
> >> > __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
> >>
> >> Although gfp_mask isn't used in cma_alloc() except no_warn, it can be used
> >> in alloc_contig_range(). For example, if passed gfp mask has no __GFP_FS,
> >> compaction(isolation) would work differently. Do you have considered
> >> such a case?
> >
> > Does any of cma_alloc users actually care about GFP_NO{FS,IO}?
> 
> I don't know. My guess is that cma_alloc() is used for DMA allocation so
> block device would use it, too. If fs/block subsystem initiates the
> request for the device,
> it would be possible that cma_alloc() is called with such a flag.
> Again, I don't know
> much about those subsystem so I would be wrong.

The patch converts existing users and none of them really tries to use
anything other than GFP_KERNEL [|__GFP_NOWARN] so this doesn't seem to
be the case. Should there be a new user requiring more restricted
gfp_mask we should carefuly re-evaluate and think how to support it.

Until then I would simply stick with the proposed approach because my
experience tells me that a wrong gfp mask usage is way too easy so the
simpler the api is the less likely we will see an abuse.
-- 
Michal Hocko
SUSE Labs

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Joonsoo Kim]

2018-07-11 17:54 GMT+09:00 Michal Hocko <mhocko@kernel.org>:
> On Wed 11-07-18 16:35:28, Joonsoo Kim wrote:
>> 2018-07-10 18:50 GMT+09:00 Michal Hocko <mhocko@kernel.org>:
>> > On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
>> >> Hello, Marek.
>> >>
>> >> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <m.szyprowski@samsung.com>:
>> >> > cma_alloc() function doesn't really support gfp flags other than
>> >> > __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
>> >>
>> >> Although gfp_mask isn't used in cma_alloc() except no_warn, it can be used
>> >> in alloc_contig_range(). For example, if passed gfp mask has no __GFP_FS,
>> >> compaction(isolation) would work differently. Do you have considered
>> >> such a case?
>> >
>> > Does any of cma_alloc users actually care about GFP_NO{FS,IO}?
>>
>> I don't know. My guess is that cma_alloc() is used for DMA allocation so
>> block device would use it, too. If fs/block subsystem initiates the
>> request for the device,
>> it would be possible that cma_alloc() is called with such a flag.
>> Again, I don't know
>> much about those subsystem so I would be wrong.
>
> The patch converts existing users and none of them really tries to use
> anything other than GFP_KERNEL [|__GFP_NOWARN] so this doesn't seem to
> be the case. Should there be a new user requiring more restricted
> gfp_mask we should carefuly re-evaluate and think how to support it.

One of existing user is general DMA layer and it takes gfp flags that is
provided by user. I don't check all the DMA allocation sites but how do
you convince that none of them try to use anything other
than GFP_KERNEL [|__GFP_NOWARN]?

Thanks.

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Christoph Hellwig]

On Thu, Jul 12, 2018 at 11:48:47AM +0900, Joonsoo Kim wrote:
> One of existing user is general DMA layer and it takes gfp flags that is
> provided by user. I don't check all the DMA allocation sites but how do
> you convince that none of them try to use anything other
> than GFP_KERNEL [|__GFP_NOWARN]?

They use a few others things still like __GFP_COMP, __GPF_DMA or
GFP_HUGEPAGE.  But all these are bogus as we have various implementations
that can't respect them.  I plan to get rid of the gfp_t argument
in the dma_map_ops alloc method in a few merge windows because of that,
but it needs further implementation consolidation first.

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Joonsoo Kim]

2018-07-12 16:15 GMT+09:00 Christoph Hellwig <hch@lst.de>:
> On Thu, Jul 12, 2018 at 11:48:47AM +0900, Joonsoo Kim wrote:
>> One of existing user is general DMA layer and it takes gfp flags that is
>> provided by user. I don't check all the DMA allocation sites but how do
>> you convince that none of them try to use anything other
>> than GFP_KERNEL [|__GFP_NOWARN]?
>
> They use a few others things still like __GFP_COMP, __GPF_DMA or
> GFP_HUGEPAGE.  But all these are bogus as we have various implementations
> that can't respect them.  I plan to get rid of the gfp_t argument
> in the dma_map_ops alloc method in a few merge windows because of that,
> but it needs further implementation consolidation first.

Okay. If those flags are all, this change would be okay.

For the remind of this gfp flag introduction in cma_alloc(), see the
following link.

https://marc.info/?l=linux-mm&m=148431452118407

Thanks.

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Vlastimil Babka]

On 07/09/2018 02:19 PM, Marek Szyprowski wrote:
> cma_alloc() function doesn't really support gfp flags other than
> __GFP_NOWARN, so convert gfp_mask parameter to boolean no_warn parameter.
> 
> This will help to avoid giving false feeling that this function supports
> standard gfp flags and callers can pass __GFP_ZERO to get zeroed buffer,
> what has already been an issue: see commit dd65a941f6ba ("arm64:
> dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag").
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

[PATCH 1/2] mm/cma: remove unsupported gfp_mask parameter from cma_alloc()

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

[PATCH 2/2] dma: remove unsupported gfp_mask parameter from dma_alloc_from_contiguous()

[Marek Szyprowski]

The CMA memory allocator doesn't support standard gfp flags for memory
allocation, so there is no point having it as a parameter for
dma_alloc_from_contiguous() function. Replace it by a boolean no_warn
argument, which covers all the underlaying cma_alloc() function supports.

This will help to avoid giving false feeling that this function supports
standard gfp flags and callers can pass __GFP_ZERO to get zeroed buffer,
what has already been an issue: see commit dd65a941f6ba ("arm64:
dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag").

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
 arch/arm/mm/dma-mapping.c      | 5 +++--
 arch/arm64/mm/dma-mapping.c    | 4 ++--
 arch/xtensa/kernel/pci-dma.c   | 2 +-
 drivers/iommu/amd_iommu.c      | 2 +-
 drivers/iommu/intel-iommu.c    | 3 ++-
 include/linux/dma-contiguous.h | 4 ++--
 kernel/dma/contiguous.c        | 7 +++----
 kernel/dma/direct.c            | 3 ++-
 8 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index be0fa7e39c26..121c6c3ba9e0 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -594,7 +594,7 @@ static void *__alloc_from_contiguous(struct device *dev, size_t size,
 	struct page *page;
 	void *ptr = NULL;
 
-	page = dma_alloc_from_contiguous(dev, count, order, gfp);
+	page = dma_alloc_from_contiguous(dev, count, order, gfp & __GFP_NOWARN);
 	if (!page)
 		return NULL;
 
@@ -1294,7 +1294,8 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
 		unsigned long order = get_order(size);
 		struct page *page;
 
-		page = dma_alloc_from_contiguous(dev, count, order, gfp);
+		page = dma_alloc_from_contiguous(dev, count, order,
+						 gfp & __GFP_NOWARN);
 		if (!page)
 			goto error;
 
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 61e93f0b5482..072c51fb07d7 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -355,7 +355,7 @@ static int __init atomic_pool_init(void)
 
 	if (dev_get_cma_area(NULL))
 		page = dma_alloc_from_contiguous(NULL, nr_pages,
-						 pool_size_order, GFP_KERNEL);
+						 pool_size_order, false);
 	else
 		page = alloc_pages(GFP_DMA32, pool_size_order);
 
@@ -573,7 +573,7 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
 		struct page *page;
 
 		page = dma_alloc_from_contiguous(dev, size >> PAGE_SHIFT,
-						 get_order(size), gfp);
+					get_order(size), gfp & __GFP_NOWARN);
 		if (!page)
 			return NULL;
 
diff --git a/arch/xtensa/kernel/pci-dma.c b/arch/xtensa/kernel/pci-dma.c
index ba4640cc0093..b2c7ba91fb08 100644
--- a/arch/xtensa/kernel/pci-dma.c
+++ b/arch/xtensa/kernel/pci-dma.c
@@ -137,7 +137,7 @@ static void *xtensa_dma_alloc(struct device *dev, size_t size,
 
 	if (gfpflags_allow_blocking(flag))
 		page = dma_alloc_from_contiguous(dev, count, get_order(size),
-						 flag);
+						 flag & __GFP_NOWARN);
 
 	if (!page)
 		page = alloc_pages(flag, get_order(size));
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 64cfe854e0f5..5ec97ffb561a 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2622,7 +2622,7 @@ static void *alloc_coherent(struct device *dev, size_t size,
 			return NULL;
 
 		page = dma_alloc_from_contiguous(dev, size >> PAGE_SHIFT,
-						 get_order(size), flag);
+					get_order(size), flag & __GFP_NOWARN);
 		if (!page)
 			return NULL;
 	}
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 869321c594e2..dd2d343428ab 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3746,7 +3746,8 @@ static void *intel_alloc_coherent(struct device *dev, size_t size,
 	if (gfpflags_allow_blocking(flags)) {
 		unsigned int count = size >> PAGE_SHIFT;
 
-		page = dma_alloc_from_contiguous(dev, count, order, flags);
+		page = dma_alloc_from_contiguous(dev, count, order,
+						 flags & __GFP_NOWARN);
 		if (page && iommu_no_mapping(dev) &&
 		    page_to_phys(page) + size > dev->coherent_dma_mask) {
 			dma_release_from_contiguous(dev, page, count);
diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
index 3c5a4cb3eb95..f247e8aa5e3d 100644
--- a/include/linux/dma-contiguous.h
+++ b/include/linux/dma-contiguous.h
@@ -112,7 +112,7 @@ static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size,
 }
 
 struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
-				       unsigned int order, gfp_t gfp_mask);
+				       unsigned int order, bool no_warn);
 bool dma_release_from_contiguous(struct device *dev, struct page *pages,
 				 int count);
 
@@ -145,7 +145,7 @@ int dma_declare_contiguous(struct device *dev, phys_addr_t size,
 
 static inline
 struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
-				       unsigned int order, gfp_t gfp_mask)
+				       unsigned int order, bool no_warn)
 {
 	return NULL;
 }
diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 19ea5d70150c..286d82329eb0 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c
@@ -178,7 +178,7 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
  * @dev:   Pointer to device for which the allocation is performed.
  * @count: Requested number of pages.
  * @align: Requested alignment of pages (in PAGE_SIZE order).
- * @gfp_mask: GFP flags to use for this allocation.
+ * @no_warn: Avoid printing message about failed allocation.
  *
  * This function allocates memory buffer for specified device. It uses
  * device specific contiguous memory area if available or the default
@@ -186,13 +186,12 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
  * function.
  */
 struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
-				       unsigned int align, gfp_t gfp_mask)
+				       unsigned int align, bool no_warn)
 {
 	if (align > CONFIG_CMA_ALIGNMENT)
 		align = CONFIG_CMA_ALIGNMENT;
 
-	return cma_alloc(dev_get_cma_area(dev), count, align,
-			 gfp_mask & __GFP_NOWARN);
+	return cma_alloc(dev_get_cma_area(dev), count, align, no_warn);
 }
 
 /**
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 8be8106270c2..e0241beeb645 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -78,7 +78,8 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 again:
 	/* CMA can be used only in the context which permits sleeping */
 	if (gfpflags_allow_blocking(gfp)) {
-		page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
+		page = dma_alloc_from_contiguous(dev, count, page_order,
+						 gfp & __GFP_NOWARN);
 		if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
 			dma_release_from_contiguous(dev, page, count);
 			page = NULL;
-- 
2.17.1

[PATCH 2/2] dma: remove unsupported gfp_mask parameter from dma_alloc_from_contiguous()

[Vlastimil Babka]

On 07/09/2018 02:19 PM, Marek Szyprowski wrote:
> The CMA memory allocator doesn't support standard gfp flags for memory
> allocation, so there is no point having it as a parameter for
> dma_alloc_from_contiguous() function. Replace it by a boolean no_warn
> argument, which covers all the underlaying cma_alloc() function supports.
> 
> This will help to avoid giving false feeling that this function supports
> standard gfp flags and callers can pass __GFP_ZERO to get zeroed buffer,
> what has already been an issue: see commit dd65a941f6ba ("arm64:
> dma-mapping: clear buffers allocated with FORCE_CONTIGUOUS flag").
> 
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

[PATCH 2/2] dma: remove unsupported gfp_mask parameter from dma_alloc_from_contiguous()

[Christoph Hellwig]

Looks good,

Reviewed-by: Christoph Hellwig <hch@lst.de>