Re: [PATCH RFC v3 5/7] mm: selftests: Add shmem into memory failure test

[Miaohe Lin <linmiaohe@huawei.com>]

On 2026/4/9 1:24, Lisa Wang wrote:
> Add a shmem memory failure selftest to test the shmem memory failure is
> correct after modifying shmem return value.
> 
> Test that
> + madvise() call returns 0 when the poisoned shmem page is clean
> + trigger a SIGBUS when the poisoned shmem page is dirty
> + trigger another SIGBUS when the poisoned shmem page is fault-in again.
> 
> Signed-off-by: Lisa Wang <wyihan@google.com>

Thanks for your patch. Two questions below.

> ---
>  tools/testing/selftests/mm/memory-failure.c | 109 +++++++++++++++++++++++++++-
>  1 file changed, 106 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/memory-failure.c b/tools/testing/selftests/mm/memory-failure.c
> index 3d9e0b9ffb41..eb3f8d98f6c9 100644
> --- a/tools/testing/selftests/mm/memory-failure.c
> +++ b/tools/testing/selftests/mm/memory-failure.c
> @@ -30,9 +30,14 @@ enum result_type {
>  	MADV_HARD_ANON,
>  	MADV_HARD_CLEAN_PAGECACHE,
>  	MADV_HARD_DIRTY_PAGECACHE,
> +	MADV_HARD_CLEAN_SHMEM,
> +	MADV_HARD_DIRTY_SHMEM,
>  	MADV_SOFT_ANON,
>  	MADV_SOFT_CLEAN_PAGECACHE,
>  	MADV_SOFT_DIRTY_PAGECACHE,
> +	MADV_SOFT_CLEAN_SHMEM,
> +	MADV_SOFT_DIRTY_SHMEM,
> +	READ_ERROR,
>  };
>  
>  static jmp_buf signal_jmp_buf;
> @@ -165,17 +170,21 @@ static void check(struct __test_metadata *_metadata, FIXTURE_DATA(memory_failure
>  	case MADV_HARD_CLEAN_PAGECACHE:
>  	case MADV_SOFT_CLEAN_PAGECACHE:
>  	case MADV_SOFT_DIRTY_PAGECACHE:
> -		/* It is not expected to receive a SIGBUS signal. */
> -		ASSERT_EQ(setjmp, 0);
> -
> +	case MADV_SOFT_DIRTY_SHMEM:
>  		/* The page content should remain unchanged. */
>  		ASSERT_TRUE(check_memory(vaddr, self->page_size));

Why we skip check_memory() for case MADV_SOFT_CLEAN_SHMEM?

> +	case MADV_HARD_CLEAN_SHMEM:
> +	case MADV_SOFT_CLEAN_SHMEM:
> +		/* It is not expected to receive a SIGBUS signal. */
> +		ASSERT_EQ(setjmp, 0);
>  
>  		/* The backing pfn of addr should have changed. */
>  		ASSERT_NE(pagemap_get_pfn(self->pagemap_fd, vaddr), self->pfn);
>  		break;
>  	case MADV_HARD_ANON:
>  	case MADV_HARD_DIRTY_PAGECACHE:
> +	case MADV_HARD_DIRTY_SHMEM:
> +	case READ_ERROR:
>  		/* The SIGBUS signal should have been received. */
>  		ASSERT_EQ(setjmp, 1);
>  
> @@ -260,6 +269,20 @@ static int prepare_file(const char *fname, unsigned long size)
>  	return fd;
>  }
>  
> +static int prepare_shmem(const char *fname, unsigned long size)
> +{
> +	int fd;
> +
> +	fd = memfd_create(fname, 0);
> +	if (fd < 0)
> +		return -1;
> +	if (ftruncate(fd, size) < 0) {
> +		close(fd);
> +		return -1;
> +	}
> +	return fd;
> +}
> +
>  /* Borrowed from mm/gup_longterm.c. */
>  static int get_fs_type(int fd)
>  {
> @@ -356,4 +379,84 @@ TEST_F(memory_failure, dirty_pagecache)
>  	ASSERT_EQ(close(fd), 0);
>  }
>  
> +TEST_F(memory_failure, dirty_shmem)
> +{
> +	int fd;
> +	char *addr;
> +	int ret;
> +
> +	fd = prepare_shmem("shmem-file", self->page_size);
> +	if (fd < 0)
> +		SKIP(return, "failed to open test shmem-file.\n");
> +
> +	addr = mmap(0, self->page_size, PROT_READ | PROT_WRITE,
> +		    MAP_SHARED, fd, 0);
> +	if (addr == MAP_FAILED) {
> +		close(fd);
> +		SKIP(return, "mmap failed, not enough memory.\n");
> +	}
> +	memset(addr, 0xce, self->page_size);
> +
> +	prepare(_metadata, self, addr);
> +
> +	ret = sigsetjmp(signal_jmp_buf, 1);
> +	if (ret == 0)
> +		ASSERT_EQ(variant->inject(self, addr), 0);
> +
> +	if (variant->type == MADV_HARD) {
> +		check(_metadata, self, addr, MADV_HARD_DIRTY_SHMEM, ret);
> +		ret = sigsetjmp(signal_jmp_buf, 1);
> +		if (ret == 0)
> +			FORCE_READ(*addr);
> +		check(_metadata, self, addr, READ_ERROR, ret);
> +	} else {

Should we always add a FORCE_READ() just after variant->inject to verify the accessibility
to the addr for soft-offline case ?

Thanks.
.

> +		check(_metadata, self, addr, MADV_SOFT_DIRTY_SHMEM, ret);> +	}
> +
> +	ASSERT_EQ(munmap(addr, self->page_size), 0);
> +
> +	ASSERT_EQ(close(fd), 0);
> +	cleanup(_metadata, self, addr);
> +}
> +
> +TEST_F(memory_failure, clean_shmem)
> +{
> +	int fd;
> +	char *addr;
> +	int ret;
> +
> +	fd = prepare_shmem("shmem-file", self->page_size);
> +	if (fd < 0)
> +		SKIP(return, "failed to open test shmem-file.\n");
> +
> +	addr = mmap(0, self->page_size, PROT_READ | PROT_WRITE,
> +		    MAP_SHARED, fd, 0);
> +	if (addr == MAP_FAILED) {
> +		close(fd);
> +		SKIP(return, "mmap failed, not enough memory.\n");
> +	}
> +	FORCE_READ(*addr);
> +
> +	prepare(_metadata, self, addr);
> +
> +	ret = sigsetjmp(signal_jmp_buf, 1);
> +	if (ret == 0)
> +		ASSERT_EQ(variant->inject(self, addr), 0);
> +
> +	if (variant->type == MADV_HARD) {
> +		check(_metadata, self, addr, MADV_HARD_CLEAN_SHMEM, ret);
> +		ret = sigsetjmp(signal_jmp_buf, 1);
> +		if (ret == 0)
> +			FORCE_READ(*addr);
> +		check(_metadata, self, addr, READ_ERROR, ret);
> +	} else {
> +		check(_metadata, self, addr, MADV_SOFT_CLEAN_SHMEM, ret);
> +	}
> +
> +	ASSERT_EQ(munmap(addr, self->page_size), 0);
> +
> +	ASSERT_EQ(close(fd), 0);
> +	cleanup(_metadata, self, addr);
> +}
> +
>  TEST_HARNESS_MAIN
>