diff mbox

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

Message ID 20180709122019eucas1p2340da484acfcc932537e6014f4fd2c29~-sqTPJKij2939229392eucas1p2j@eucas1p2.samsung.com (mailing list archive)
State New, archived
Headers show

Commit Message

Marek Szyprowski July 9, 2018, 12:19 p.m. UTC
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(-)

Comments

Michal Hocko July 9, 2018, 1:09 p.m. UTC | #1
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
>
Michał Nazarewicz July 9, 2018, 2:23 p.m. UTC | #2
On Mon, 9 Jul 2018 13:20 Marek Szyprowski, <m.szyprowski@samsung.com> 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: Michał Nazarewicz <mina86@mina86.com>

(Adding Acked-by on a phone is surprisingly hard).

---
>  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(-)
>
Laura Abbott July 9, 2018, 5:27 p.m. UTC | #3
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;
>
Joonsoo Kim July 10, 2018, 7:19 a.m. UTC | #4
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.
Michal Hocko July 10, 2018, 9:50 a.m. UTC | #5
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}?
Joonsoo Kim July 11, 2018, 7:35 a.m. UTC | #6
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.
Michal Hocko July 11, 2018, 8:54 a.m. UTC | #7
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.
Joonsoo Kim July 12, 2018, 2:48 a.m. UTC | #8
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.
Christoph Hellwig July 12, 2018, 7:15 a.m. UTC | #9
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.
Joonsoo Kim July 13, 2018, 6:29 a.m. UTC | #10
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.
Vlastimil Babka July 16, 2018, 7:45 a.m. UTC | #11
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>
Christoph Hellwig July 17, 2018, 3:08 p.m. UTC | #12
Looks good:

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

Patch

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;