* [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark
@ 2026-05-12 10:13 Hongfu Li
2026-05-12 10:33 ` David Hildenbrand (Arm)
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: Hongfu Li @ 2026-05-12 10:13 UTC (permalink / raw)
To: jgg, leon, akpm, david, ljs, vbabka, rppt, surenb, mhocko, shuah
Cc: linux-mm, linux-kselftest, linux-kernel, Hongfu Li
mmap() returns MAP_FAILED on error, not NULL. The current check uses
!buffer->ptr, which evaluates to false when mmap() fails (since
MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
---
tools/testing/selftests/mm/hmm-tests.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
index 788689497e92..d72adba5c74e 100644
--- a/tools/testing/selftests/mm/hmm-tests.c
+++ b/tools/testing/selftests/mm/hmm-tests.c
@@ -2688,7 +2688,7 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz
buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
- if (!buffer->ptr)
+ if (buffer->ptr == MAP_FAILED)
return -1;
/* Apply THP hint if requested */
--
2.25.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark
2026-05-12 10:13 [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark Hongfu Li
@ 2026-05-12 10:33 ` David Hildenbrand (Arm)
2026-05-12 11:13 ` Dev Jain
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: David Hildenbrand (Arm) @ 2026-05-12 10:33 UTC (permalink / raw)
To: Hongfu Li, jgg, leon, akpm, ljs, vbabka, rppt, surenb, mhocko,
shuah
Cc: linux-mm, linux-kselftest, linux-kernel
On 5/12/26 12:13, Hongfu Li wrote:
> mmap() returns MAP_FAILED on error, not NULL. The current check uses
> !buffer->ptr, which evaluates to false when mmap() fails (since
> MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
> ---
> tools/testing/selftests/mm/hmm-tests.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 788689497e92..d72adba5c74e 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2688,7 +2688,7 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz
> buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>
> - if (!buffer->ptr)
> + if (buffer->ptr == MAP_FAILED)
> return -1;
>
> /* Apply THP hint if requested */
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark
2026-05-12 10:13 [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark Hongfu Li
2026-05-12 10:33 ` David Hildenbrand (Arm)
@ 2026-05-12 11:13 ` Dev Jain
2026-05-12 12:21 ` Mike Rapoport
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Dev Jain @ 2026-05-12 11:13 UTC (permalink / raw)
To: Hongfu Li, jgg, leon, akpm, david, ljs, vbabka, rppt, surenb,
mhocko, shuah
Cc: linux-mm, linux-kselftest, linux-kernel
On 12/05/26 3:43 pm, Hongfu Li wrote:
> mmap() returns MAP_FAILED on error, not NULL. The current check uses
> !buffer->ptr, which evaluates to false when mmap() fails (since
> MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
> ---
Reviewed-by: Dev Jain <dev.jain@arm.com>
> tools/testing/selftests/mm/hmm-tests.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 788689497e92..d72adba5c74e 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2688,7 +2688,7 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz
> buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>
> - if (!buffer->ptr)
> + if (buffer->ptr == MAP_FAILED)
> return -1;
>
> /* Apply THP hint if requested */
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark
2026-05-12 10:13 [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark Hongfu Li
2026-05-12 10:33 ` David Hildenbrand (Arm)
2026-05-12 11:13 ` Dev Jain
@ 2026-05-12 12:21 ` Mike Rapoport
2026-05-12 12:57 ` Donet Tom
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: Mike Rapoport @ 2026-05-12 12:21 UTC (permalink / raw)
To: Hongfu Li
Cc: jgg, leon, akpm, david, ljs, vbabka, surenb, mhocko, shuah,
linux-mm, linux-kselftest, linux-kernel
On Tue, May 12, 2026 at 06:13:05PM +0800, Hongfu Li wrote:
> mmap() returns MAP_FAILED on error, not NULL. The current check uses
> !buffer->ptr, which evaluates to false when mmap() fails (since
> MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
> tools/testing/selftests/mm/hmm-tests.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 788689497e92..d72adba5c74e 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2688,7 +2688,7 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz
> buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>
> - if (!buffer->ptr)
> + if (buffer->ptr == MAP_FAILED)
> return -1;
>
> /* Apply THP hint if requested */
> --
> 2.25.1
>
--
Sincerely yours,
Mike.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark
2026-05-12 10:13 [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark Hongfu Li
` (2 preceding siblings ...)
2026-05-12 12:21 ` Mike Rapoport
@ 2026-05-12 12:57 ` Donet Tom
2026-05-12 14:06 ` Lorenzo Stoakes
2026-05-13 0:42 ` SeongJae Park
5 siblings, 0 replies; 7+ messages in thread
From: Donet Tom @ 2026-05-12 12:57 UTC (permalink / raw)
To: Hongfu Li, jgg, leon, akpm, david, ljs, vbabka, rppt, surenb,
mhocko, shuah
Cc: linux-mm, linux-kselftest, linux-kernel
On 5/12/26 3:43 PM, Hongfu Li wrote:
> mmap() returns MAP_FAILED on error, not NULL. The current check uses
> !buffer->ptr, which evaluates to false when mmap() fails (since
> MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
LGTM
Reviewed-by: Donet Tom <donettom@linux.ibm.com>
> ---
> tools/testing/selftests/mm/hmm-tests.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 788689497e92..d72adba5c74e 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2688,7 +2688,7 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz
> buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>
> - if (!buffer->ptr)
> + if (buffer->ptr == MAP_FAILED)
> return -1;
>
> /* Apply THP hint if requested */
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark
2026-05-12 10:13 [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark Hongfu Li
` (3 preceding siblings ...)
2026-05-12 12:57 ` Donet Tom
@ 2026-05-12 14:06 ` Lorenzo Stoakes
2026-05-13 0:42 ` SeongJae Park
5 siblings, 0 replies; 7+ messages in thread
From: Lorenzo Stoakes @ 2026-05-12 14:06 UTC (permalink / raw)
To: Hongfu Li
Cc: jgg, leon, akpm, david, vbabka, rppt, surenb, mhocko, shuah,
linux-mm, linux-kselftest, linux-kernel
On Tue, May 12, 2026 at 06:13:05PM +0800, Hongfu Li wrote:
> mmap() returns MAP_FAILED on error, not NULL. The current check uses
> !buffer->ptr, which evaluates to false when mmap() fails (since
> MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
LGTM, so:
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
> ---
> tools/testing/selftests/mm/hmm-tests.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 788689497e92..d72adba5c74e 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2688,7 +2688,7 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz
> buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>
> - if (!buffer->ptr)
> + if (buffer->ptr == MAP_FAILED)
> return -1;
>
> /* Apply THP hint if requested */
> --
> 2.25.1
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark
2026-05-12 10:13 [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark Hongfu Li
` (4 preceding siblings ...)
2026-05-12 14:06 ` Lorenzo Stoakes
@ 2026-05-13 0:42 ` SeongJae Park
5 siblings, 0 replies; 7+ messages in thread
From: SeongJae Park @ 2026-05-13 0:42 UTC (permalink / raw)
To: Hongfu Li
Cc: SeongJae Park, jgg, leon, akpm, david, ljs, vbabka, rppt, surenb,
mhocko, shuah, linux-mm, linux-kselftest, linux-kernel
On Tue, 12 May 2026 18:13:05 +0800 Hongfu Li <lihongfu@kylinos.cn> wrote:
> mmap() returns MAP_FAILED on error, not NULL. The current check uses
> !buffer->ptr, which evaluates to false when mmap() fails (since
> MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
Good catch, thank you!
>
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Reviewed-by: SeongJae Park <sj@kernel.org>
Thanks,
SJ
[...]
^ permalink raw reply [flat|nested] 7+ messages in thread
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2026-05-12 10:13 [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark Hongfu Li
2026-05-12 10:33 ` David Hildenbrand (Arm)
2026-05-12 11:13 ` Dev Jain
2026-05-12 12:21 ` Mike Rapoport
2026-05-12 12:57 ` Donet Tom
2026-05-12 14:06 ` Lorenzo Stoakes
2026-05-13 0:42 ` SeongJae Park
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