linux-kernel - Re: [PATCH v2 9/9] memfd-test: run fuse test on hugetlb backend memory

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Date:   Mon, 6 Nov 2017 17:41:16 -0800
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Marc-André Lureau <marcandre.lureau@...hat.com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     aarcange@...hat.com, hughd@...gle.com, nyc@...omorphy.com
Subject: Re: [PATCH v2 9/9] memfd-test: run fuse test on hugetlb backend
 memory

On 11/06/2017 06:39 AM, Marc-André Lureau wrote:
> Suggested-by: Mike Kravetz <mike.kravetz@...cle.com>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@...hat.com>
> ---
>  tools/testing/selftests/memfd/fuse_test.c      | 30 ++++++++++++++++++++++----
>  tools/testing/selftests/memfd/run_fuse_test.sh |  2 +-
>  tools/testing/selftests/memfd/run_tests.sh     |  1 +
>  3 files changed, 28 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/testing/selftests/memfd/fuse_test.c b/tools/testing/selftests/memfd/fuse_test.c
> index 795a25ba8521..0a85b34929e1 100644
> --- a/tools/testing/selftests/memfd/fuse_test.c
> +++ b/tools/testing/selftests/memfd/fuse_test.c
> @@ -38,6 +38,8 @@
>  #define MFD_DEF_SIZE 8192
>  #define STACK_SIZE 65536
>  
> +static size_t mfd_def_size = MFD_DEF_SIZE;
> +
>  static int mfd_assert_new(const char *name, loff_t sz, unsigned int flags)
>  {
>  	int r, fd;
> @@ -123,7 +125,7 @@ static void *mfd_assert_mmap_shared(int fd)
>  	void *p;
>  
>  	p = mmap(NULL,
> -		 MFD_DEF_SIZE,
> +		 mfd_def_size,
>  		 PROT_READ | PROT_WRITE,
>  		 MAP_SHARED,
>  		 fd,
> @@ -141,7 +143,7 @@ static void *mfd_assert_mmap_private(int fd)
>  	void *p;
>  
>  	p = mmap(NULL,
> -		 MFD_DEF_SIZE,
> +		 mfd_def_size,
>  		 PROT_READ | PROT_WRITE,
>  		 MAP_PRIVATE,
>  		 fd,
> @@ -174,7 +176,7 @@ static int sealing_thread_fn(void *arg)
>  	usleep(200000);
>  
>  	/* unmount mapping before sealing to avoid i_mmap_writable failures */
> -	munmap(global_p, MFD_DEF_SIZE);
> +	munmap(global_p, mfd_def_size);
>  
>  	/* Try sealing the global file; expect EBUSY or success. Current
>  	 * kernels will never succeed, but in the future, kernels might
> @@ -224,7 +226,7 @@ static void join_sealing_thread(pid_t pid)
>  
>  int main(int argc, char **argv)
>  {
> -	static const char zero[MFD_DEF_SIZE];
> +	char *zero;
>  	int fd, mfd, r;
>  	void *p;
>  	int was_sealed;
> @@ -235,6 +237,25 @@ int main(int argc, char **argv)
>  		abort();
>  	}
>  
> +	if (argc >= 3) {
> +		if (!strcmp(argv[2], "hugetlbfs")) {
> +			unsigned long hpage_size = default_huge_page_size();
> +
> +			if (!hpage_size) {
> +				printf("Unable to determine huge page size\n");
> +				abort();
> +			}
> +
> +			hugetlbfs_test = 1;
> +			mfd_def_size = hpage_size * 2;
> +		} else {
> +			printf("Unknown option: %s\n", argv[2]);
> +			abort();
> +		}
> +	}
> +
> +	zero = calloc(sizeof(*zero), mfd_def_size);
> +
>  	/* open FUSE memfd file for GUP testing */
>  	printf("opening: %s\n", argv[1]);
>  	fd = open(argv[1], O_RDONLY | O_CLOEXEC);

When ftruncate'ing the newly created file, you need to make sure length is
a multiple of huge page size for hugetlbfs files.  So, you will want to
do something like:

--- a/tools/testing/selftests/memfd/fuse_test.c
+++ b/tools/testing/selftests/memfd/fuse_test.c
@@ -265,7 +265,7 @@ int main(int argc, char **argv)
 
        /* create new memfd-object */
        mfd = mfd_assert_new("kern_memfd_fuse",
-                            MFD_DEF_SIZE,
+                            mfd_def_size,
                             MFD_CLOEXEC | MFD_ALLOW_SEALING);
 
        /* mmap memfd-object for writing */

Leaving MFD_DEF_SIZE for the size of reads and writes should be fine.

-- 
Mike Kravetz

> @@ -303,6 +324,7 @@ int main(int argc, char **argv)
>  	close(fd);
>  
>  	printf("fuse: DONE\n");
> +	free(zero);
>  
>  	return 0;
>  }
> diff --git a/tools/testing/selftests/memfd/run_fuse_test.sh b/tools/testing/selftests/memfd/run_fuse_test.sh
> index 407df68dfe27..22e572e2d66a 100755
> --- a/tools/testing/selftests/memfd/run_fuse_test.sh
> +++ b/tools/testing/selftests/memfd/run_fuse_test.sh
> @@ -10,6 +10,6 @@ set -e
>  
>  mkdir mnt
>  ./fuse_mnt ./mnt
> -./fuse_test ./mnt/memfd
> +./fuse_test ./mnt/memfd $@
>  fusermount -u ./mnt
>  rmdir ./mnt
> diff --git a/tools/testing/selftests/memfd/run_tests.sh b/tools/testing/selftests/memfd/run_tests.sh
> index daabb350697c..c2d41ed81b24 100755
> --- a/tools/testing/selftests/memfd/run_tests.sh
> +++ b/tools/testing/selftests/memfd/run_tests.sh
> @@ -60,6 +60,7 @@ fi
>  # Run the hugetlbfs test
>  #
>  ./memfd_test hugetlbfs
> +./run_fuse_test.sh hugetlbfs
>  
>  #
>  # Give back any huge pages allocated for the test
>