Re: [PATCH v5 11/14] selftests/mm: remove READ_ONLY_THP_FOR_FS in khugepaged

["David Hildenbrand (Arm)" <david@kernel.org>]

On 4/29/26 17:35, Zi Yan wrote:
> Change the requirement to a file system with large folio support and the
> supported order needs to include PMD_ORDER.
> 
> Also add tests of opening a file with read write permission and populating
> folios with writes. Reuse the XFS image from split_huge_page_test.
> 
> Signed-off-by: Zi Yan <ziy@nvidia.com>
> ---
>  tools/testing/selftests/mm/khugepaged.c   | 131 +++++++++++++++-------
>  tools/testing/selftests/mm/run_vmtests.sh |  12 +-
>  2 files changed, 102 insertions(+), 41 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
> index a6bb9d50363d2..80b913185c643 100644
> --- a/tools/testing/selftests/mm/khugepaged.c
> +++ b/tools/testing/selftests/mm/khugepaged.c
> @@ -49,7 +49,8 @@ struct mem_ops {
>  	const char *name;
>  };
>  
> -static struct mem_ops *file_ops;
> +static struct mem_ops *read_only_file_ops;
> +static struct mem_ops *read_write_file_ops;
>  static struct mem_ops *anon_ops;
>  static struct mem_ops *shmem_ops;
>  
> @@ -112,7 +113,8 @@ static void restore_settings(int sig)
>  static void save_settings(void)
>  {
>  	printf("Save THP and khugepaged settings...");
> -	if (file_ops && finfo.type == VMA_FILE)
> +	if ((read_only_file_ops || read_write_file_ops) &&
> +	    finfo.type == VMA_FILE)
>  		thp_set_read_ahead_path(finfo.dev_queue_read_ahead_path);
>  	thp_save_settings();
>  
> @@ -364,11 +366,14 @@ static bool anon_check_huge(void *addr, int nr_hpages)
>  	return check_huge_anon(addr, nr_hpages, hpage_pmd_size);
>  }
>  
> -static void *file_setup_area(int nr_hpages)
> +static void *file_setup_area_common(int nr_hpages, bool read_only)
>  {
>  	int fd;
>  	void *p;
>  	unsigned long size;
> +	int open_opt = read_only ? O_RDONLY : O_RDWR;
> +	int mmap_prot = read_only ? PROT_READ : (PROT_READ | PROT_WRITE);
> +	int mmap_opt = read_only ? MAP_PRIVATE : MAP_SHARED;

Can all be const and read better at the very top of the list.

Why do we go from private->shared depending on "read_only" parameter? I'd assume
we'd want to test MAP_SHARED for both (read-only + read-write)?


>  
>  	unlink(finfo.path);  /* Cleanup from previous failed tests */
>  	printf("Creating %s for collapse%s...", finfo.path,
> @@ -399,14 +404,15 @@ static void *file_setup_area(int nr_hpages)
>  	munmap(p, size);
>  	success("OK");
>  
> -	printf("Opening %s read only for collapse...", finfo.path);
> -	finfo.fd = open(finfo.path, O_RDONLY, 777);
> +	printf("Opening %s %s for collapse...", finfo.path,
> +	       read_only ? "read only" : "read-write");

"read-only" ?

> +	finfo.fd = open(finfo.path, open_opt, 777);
>  	if (finfo.fd < 0) {
>  		perror("open()");
>  		exit(EXIT_FAILURE);
>  	}
> -	p = mmap(BASE_ADDR, size, PROT_READ,
> -		 MAP_PRIVATE, finfo.fd, 0);
> +	p = mmap(BASE_ADDR, size, mmap_prot,
> +		 mmap_opt, finfo.fd, 0);

While at it, can fit that into a single line.

>  	if (p == MAP_FAILED || p != BASE_ADDR) {
>  		perror("mmap()");
>  		exit(EXIT_FAILURE);
> @@ -418,6 +424,16 @@ static void *file_setup_area(int nr_hpages)
>  	return p;
>  }
>  
> +static void *file_setup_read_only_area(int nr_hpages)
> +{
> +	return file_setup_area_common(nr_hpages, /* read_only= */ true);
> +}
> +
> +static void *file_setup_read_write_area(int nr_hpages)
> +{
> +	return file_setup_area_common(nr_hpages, /* read_only= */ false);
> +}
> +
>  static void file_cleanup_area(void *p, unsigned long size)
>  {
>  	munmap(p, size);
> @@ -425,14 +441,25 @@ static void file_cleanup_area(void *p, unsigned long size)
>  	unlink(finfo.path);
>  }
>  
> -static void file_fault(void *p, unsigned long start, unsigned long end)
> +static void file_fault_common(void *p, unsigned long start, unsigned long end,
> +		int madv_ops)
>  {
> -	if (madvise(((char *)p) + start, end - start, MADV_POPULATE_READ)) {
> +	if (madvise(((char *)p) + start, end - start, madv_ops)) {
>  		perror("madvise(MADV_POPULATE_READ");
>  		exit(EXIT_FAILURE);
>  	}
>  }
>  
> +static void file_fault_read(void *p, unsigned long start, unsigned long end)
> +{
> +	file_fault_common(p, start, end, MADV_POPULATE_READ);

Do we really want file_fault_common()? I'd say, just inline it. In particular
avoids checking the madv_ops to figure out the error message ...

> +}
> +
> +static void file_fault_write(void *p, unsigned long start, unsigned long end)
> +{
> +	file_fault_common(p, start, end, MADV_POPULATE_WRITE);
> +}
> +
>  static bool file_check_huge(void *addr, int nr_hpages)
>  {
>  	switch (finfo.type) {
> @@ -488,10 +515,18 @@ static struct mem_ops __anon_ops = {
>  	.name = "anon",
>  };

[...]

>  };
>  
> +static bool is_tmpfs(struct mem_ops *ops)
> +{
> +	return (ops == &__read_only_file_ops ||
> +		ops == &__read_write_file_ops) &&

Can't this fit into two lines?

> +	       finfo.type == VMA_SHMEM;
> +}
> +
> +static bool is_anon(struct mem_ops *ops)
> +{
> +	return ops == &__anon_ops;
> +}
> +
>  static void __madvise_collapse(const char *msg, char *p, int nr_hpages,
>  			       struct mem_ops *ops, bool expect)
>  {

> -
>  static void alloc_at_fault(void)
>  {
>  	struct thp_settings settings = *thp_current_settings();
> @@ -1097,8 +1142,8 @@ static void usage(void)
>  	fprintf(stderr, "\t<context>\t: [all|khugepaged|madvise]\n");
>  	fprintf(stderr, "\t<mem_type>\t: [all|anon|file|shmem]\n");
>  	fprintf(stderr, "\n\t\"file,all\" mem_type requires [dir] argument\n");
> -	fprintf(stderr, "\n\t\"file,all\" mem_type requires kernel built with\n");
> -	fprintf(stderr,	"\tCONFIG_READ_ONLY_THP_FOR_FS=y\n");
> +	fprintf(stderr, "\n\t\"file,all\" mem_type requires a file system\n");
> +	fprintf(stderr,	"\twith large folio support (order >= PMD order)\n");

"with PMD-sized large folio support"?

>  	fprintf(stderr, "\n\tif [dir] is a (sub)directory of a tmpfs mount, tmpfs must be\n");
>  	fprintf(stderr,	"\tmounted with huge=advise option for khugepaged tests to work\n");
>  	fprintf(stderr,	"\n\tSupported Options:\n");
> @@ -1154,20 +1199,22 @@ static void parse_test_type(int argc, char **argv)
>  		usage();
-- 
Cheers,

David