[PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[Zi Yan]

When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement
with side effect inside it is incorrect. Collect all !put_page_testzero()
results and check the sum using WARN instead after the loop. It restores
the same check in free_contig_range() before commit
e0c1326779cc ("mm: page_alloc: add alloc_contig_frozen_{range,pages}()"),
the commit prior to the Fixes one.

Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()")
Reported-by: Ron Economos <re@w6rz.net>
Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada885@w6rz.net/
Suggested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zi Yan <ziy@nvidia.com>
---
From V2:
- Collect !put_page_testzero() to get the right result.

From V1:
- Collect all put_page_testzero() results and do a single WARN after the
  loop.

 mm/cma.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/cma.c b/mm/cma.c
index 94b5da468a7d..15cc0ae76c8e 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct page *pages,
 		 unsigned long count)
 {
 	struct cma_memrange *cmr;
+	unsigned long ret = 0;
 	unsigned long i, pfn;
 
 	cmr = find_cma_memrange(cma, pages, count);
@@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct page *pages,
 
 	pfn = page_to_pfn(pages);
 	for (i = 0; i < count; i++, pfn++)
-		VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)));
+		ret += !put_page_testzero(pfn_to_page(pfn));
+
+	WARN(ret, "%lu pages are still in use!\n", ret);
 
 	__cma_release_frozen(cma, cmr, pages, count);
 
-- 
2.51.0

Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[Anshuman Khandual]

On 25/02/26 8:42 AM, Zi Yan wrote:
> When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement
> with side effect inside it is incorrect. Collect all !put_page_testzero()
> results and check the sum using WARN instead after the loop. It restores
> the same check in free_contig_range() before commit
> e0c1326779cc ("mm: page_alloc: add alloc_contig_frozen_{range,pages}()"),
> the commit prior to the Fixes one.
> 
> Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()")
> Reported-by: Ron Economos <re@w6rz.net>
> Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada885@w6rz.net/
> Suggested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
> From V2:
> - Collect !put_page_testzero() to get the right result.
> 
> From V1:
> - Collect all put_page_testzero() results and do a single WARN after the
>   loop.
> 
>  mm/cma.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index 94b5da468a7d..15cc0ae76c8e 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct page *pages,
>  		 unsigned long count)
>  {
>  	struct cma_memrange *cmr;
> +	unsigned long ret = 0;
>  	unsigned long i, pfn;
>  
>  	cmr = find_cma_memrange(cma, pages, count);
> @@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct page *pages,
>  
>  	pfn = page_to_pfn(pages);
>  	for (i = 0; i < count; i++, pfn++)
> -		VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)));
> +		ret += !put_page_testzero(pfn_to_page(pfn));
> +
> +	WARN(ret, "%lu pages are still in use!\n", ret);
>  
>  	__cma_release_frozen(cma, cmr, pages, count);
>  

Makes sense to make the above warning unconditional regardless of CONFIG_DEBUG_VM.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[Kefeng Wang]

On 2026/2/25 11:12, Zi Yan wrote:
> When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement
> with side effect inside it is incorrect. Collect all !put_page_testzero()
> results and check the sum using WARN instead after the loop. It restores
> the same check in free_contig_range() before commit
> e0c1326779cc ("mm: page_alloc: add alloc_contig_frozen_{range,pages}()"),
> the commit prior to the Fixes one.
> 
> Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()")
> Reported-by: Ron Economos <re@w6rz.net>
> Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada885@w6rz.net/
> Suggested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  From V2:
> - Collect !put_page_testzero() to get the right result.
> 
>  From V1:
> - Collect all put_page_testzero() results and do a single WARN after the
>    loop.
> 


Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>

>   mm/cma.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index 94b5da468a7d..15cc0ae76c8e 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct page *pages,
>   		 unsigned long count)
>   {
>   	struct cma_memrange *cmr;
> +	unsigned long ret = 0;
>   	unsigned long i, pfn;
>   
>   	cmr = find_cma_memrange(cma, pages, count);
> @@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct page *pages,
>   
>   	pfn = page_to_pfn(pages);
>   	for (i = 0; i < count; i++, pfn++)
> -		VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)));
> +		ret += !put_page_testzero(pfn_to_page(pfn));
> +
> +	WARN(ret, "%lu pages are still in use!\n", ret);
>   
>   	__cma_release_frozen(cma, cmr, pages, count);
>   

Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[Ron Economos]

On 2/24/26 19:12, Zi Yan wrote:
> When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement
> with side effect inside it is incorrect. Collect all !put_page_testzero()
> results and check the sum using WARN instead after the loop. It restores
> the same check in free_contig_range() before commit
> e0c1326779cc ("mm: page_alloc: add alloc_contig_frozen_{range,pages}()"),
> the commit prior to the Fixes one.
>
> Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()")
> Reported-by: Ron Economos <re@w6rz.net>
> Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada885@w6rz.net/
> Suggested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  From V2:
> - Collect !put_page_testzero() to get the right result.
>
>  From V1:
> - Collect all put_page_testzero() results and do a single WARN after the
>    loop.
>
>   mm/cma.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index 94b5da468a7d..15cc0ae76c8e 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct page *pages,
>   		 unsigned long count)
>   {
>   	struct cma_memrange *cmr;
> +	unsigned long ret = 0;
>   	unsigned long i, pfn;
>   
>   	cmr = find_cma_memrange(cma, pages, count);
> @@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct page *pages,
>   
>   	pfn = page_to_pfn(pages);
>   	for (i = 0; i < count; i++, pfn++)
> -		VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)));
> +		ret += !put_page_testzero(pfn_to_page(pfn));
> +
> +	WARN(ret, "%lu pages are still in use!\n", ret);
>   
>   	__cma_release_frozen(cma, cmr, pages, count);

Tested-by: Ron Economos <re@w6rz>

Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[Ron Economos]

On 2/24/26 19:12, Zi Yan wrote:
> When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement
> with side effect inside it is incorrect. Collect all !put_page_testzero()
> results and check the sum using WARN instead after the loop. It restores
> the same check in free_contig_range() before commit
> e0c1326779cc ("mm: page_alloc: add alloc_contig_frozen_{range,pages}()"),
> the commit prior to the Fixes one.
>
> Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()")
> Reported-by: Ron Economos <re@w6rz.net>
> Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada885@w6rz.net/
> Suggested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  From V2:
> - Collect !put_page_testzero() to get the right result.
>
>  From V1:
> - Collect all put_page_testzero() results and do a single WARN after the
>    loop.
>
>   mm/cma.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index 94b5da468a7d..15cc0ae76c8e 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct page *pages,
>   		 unsigned long count)
>   {
>   	struct cma_memrange *cmr;
> +	unsigned long ret = 0;
>   	unsigned long i, pfn;
>   
>   	cmr = find_cma_memrange(cma, pages, count);
> @@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct page *pages,
>   
>   	pfn = page_to_pfn(pages);
>   	for (i = 0; i < count; i++, pfn++)
> -		VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)));
> +		ret += !put_page_testzero(pfn_to_page(pfn));
> +
> +	WARN(ret, "%lu pages are still in use!\n", ret);
>   
>   	__cma_release_frozen(cma, cmr, pages, count);

Tested-by: Ron Economos <re@w6rz.net>

Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[David Hildenbrand (Arm)]

On 2/25/26 04:12, Zi Yan wrote:
> When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement
> with side effect inside it is incorrect. Collect all !put_page_testzero()
> results and check the sum using WARN instead after the loop. It restores
> the same check in free_contig_range() before commit
> e0c1326779cc ("mm: page_alloc: add alloc_contig_frozen_{range,pages}()"),
> the commit prior to the Fixes one.
> 
> Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()")
> Reported-by: Ron Economos <re@w6rz.net>
> Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada885@w6rz.net/
> Suggested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
> From V2:
> - Collect !put_page_testzero() to get the right result.
> 
> From V1:
> - Collect all put_page_testzero() results and do a single WARN after the
>   loop.
> 
>  mm/cma.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index 94b5da468a7d..15cc0ae76c8e 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct page *pages,
>  		 unsigned long count)
>  {
>  	struct cma_memrange *cmr;
> +	unsigned long ret = 0;
>  	unsigned long i, pfn;
>  
>  	cmr = find_cma_memrange(cma, pages, count);
> @@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct page *pages,
>  
>  	pfn = page_to_pfn(pages);
>  	for (i = 0; i < count; i++, pfn++)
> -		VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn)));
> +		ret += !put_page_testzero(pfn_to_page(pfn));
> +
> +	WARN(ret, "%lu pages are still in use!\n", ret);
>  
>  	__cma_release_frozen(cma, cmr, pages, count);
>  

Thanks for taking care of the fix.

Debugged-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David

Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()

[Vishal Moola (Oracle)]

On Tue, Feb 24, 2026 at 10:12:31PM -0500, Zi Yan wrote:
> When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any statement
> with side effect inside it is incorrect. Collect all !put_page_testzero()
> results and check the sum using WARN instead after the loop. It restores
> the same check in free_contig_range() before commit
> e0c1326779cc ("mm: page_alloc: add alloc_contig_frozen_{range,pages}()"),
> the commit prior to the Fixes one.

LGTM.

Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>