* Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()
2026-02-25 3:12 [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release() Zi Yan
@ 2026-02-25 5:53 ` Anshuman Khandual
2026-02-25 6:27 ` Kefeng Wang
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Anshuman Khandual @ 2026-02-25 5:53 UTC (permalink / raw)
To: Zi Yan, Andrew Morton
Cc: David Hildenbrand, Lorenzo Stoakes, Liam R. Howlett,
Vlastimil Babka, Mike Rapoport, Suren Baghdasaryan, Michal Hocko,
Kefeng Wang, linux-mm, linux-kernel, SeongJae Park, Ron Economos
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>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()
2026-02-25 3:12 [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release() Zi Yan
2026-02-25 5:53 ` Anshuman Khandual
@ 2026-02-25 6:27 ` Kefeng Wang
2026-02-25 8:15 ` Ron Economos
2026-02-25 8:20 ` Ron Economos
3 siblings, 0 replies; 5+ messages in thread
From: Kefeng Wang @ 2026-02-25 6:27 UTC (permalink / raw)
To: Zi Yan, Andrew Morton
Cc: David Hildenbrand, Lorenzo Stoakes, Liam R. Howlett,
Vlastimil Babka, Mike Rapoport, Suren Baghdasaryan, Michal Hocko,
linux-mm, linux-kernel, SeongJae Park, Ron Economos
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);
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()
2026-02-25 3:12 [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release() Zi Yan
2026-02-25 5:53 ` Anshuman Khandual
2026-02-25 6:27 ` Kefeng Wang
@ 2026-02-25 8:15 ` Ron Economos
2026-02-25 8:20 ` Ron Economos
3 siblings, 0 replies; 5+ messages in thread
From: Ron Economos @ 2026-02-25 8:15 UTC (permalink / raw)
To: Zi Yan, Andrew Morton
Cc: David Hildenbrand, Lorenzo Stoakes, Liam R. Howlett,
Vlastimil Babka, Mike Rapoport, Suren Baghdasaryan, Michal Hocko,
Kefeng Wang, linux-mm, linux-kernel, SeongJae Park
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>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release()
2026-02-25 3:12 [PATCH v3] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release() Zi Yan
` (2 preceding siblings ...)
2026-02-25 8:15 ` Ron Economos
@ 2026-02-25 8:20 ` Ron Economos
3 siblings, 0 replies; 5+ messages in thread
From: Ron Economos @ 2026-02-25 8:20 UTC (permalink / raw)
To: Zi Yan, Andrew Morton
Cc: David Hildenbrand, Lorenzo Stoakes, Liam R. Howlett,
Vlastimil Babka, Mike Rapoport, Suren Baghdasaryan, Michal Hocko,
Kefeng Wang, linux-mm, linux-kernel, SeongJae Park
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>
^ permalink raw reply [flat|nested] 5+ messages in thread