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 <[email protected]>
---
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
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 <[email protected]>
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 <[email protected]>
> ---
> 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
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 <[email protected]>
> Signed-off-by: Marek Szyprowski <[email protected]>
> ---
> 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;
>
Hello, Marek.
2018-07-09 21:19 GMT+09:00 Marek Szyprowski <[email protected]>:
> 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.
On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
> Hello, Marek.
>
> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <[email protected]>:
> > 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
2018-07-10 18:50 GMT+09:00 Michal Hocko <[email protected]>:
> On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
>> Hello, Marek.
>>
>> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <[email protected]>:
>> > 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.
On Wed 11-07-18 16:35:28, Joonsoo Kim wrote:
> 2018-07-10 18:50 GMT+09:00 Michal Hocko <[email protected]>:
> > On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
> >> Hello, Marek.
> >>
> >> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <[email protected]>:
> >> > 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
2018-07-11 17:54 GMT+09:00 Michal Hocko <[email protected]>:
> On Wed 11-07-18 16:35:28, Joonsoo Kim wrote:
>> 2018-07-10 18:50 GMT+09:00 Michal Hocko <[email protected]>:
>> > On Tue 10-07-18 16:19:32, Joonsoo Kim wrote:
>> >> Hello, Marek.
>> >>
>> >> 2018-07-09 21:19 GMT+09:00 Marek Szyprowski <[email protected]>:
>> >> > 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.
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.
2018-07-12 16:15 GMT+09:00 Christoph Hellwig <[email protected]>:
> 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.
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 <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Looks good:
Reviewed-by: Christoph Hellwig <[email protected]>