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Message-ID: <YvSj2h7WgV1xd2Ht@kernel.org>
Date: Thu, 11 Aug 2022 09:38:18 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Axel Rasmussen <axelrasmussen@...gle.com>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"Dmitry V . Levin" <ldv@...linux.org>,
Gleb Fotengauer-Malinovskiy <glebfm@...linux.org>,
Hugh Dickins <hughd@...gle.com>, Jan Kara <jack@...e.cz>,
Jonathan Corbet <corbet@....net>,
Mel Gorman <mgorman@...hsingularity.net>,
Mike Kravetz <mike.kravetz@...cle.com>,
Nadav Amit <namit@...are.com>, Peter Xu <peterx@...hat.com>,
Shuah Khan <shuah@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Vlastimil Babka <vbabka@...e.cz>,
zhangyi <yi.zhang@...wei.com>, linux-doc@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
linux-security-module@...r.kernel.org
Subject: Re: [PATCH v5 3/5] userfaultfd: selftests: modify selftest to use
/dev/userfaultfd
On Mon, Aug 08, 2022 at 10:56:12AM -0700, Axel Rasmussen wrote:
> We clearly want to ensure both userfaultfd(2) and /dev/userfaultfd keep
> working into the future, so just run the test twice, using each
> interface.
>
> Instead of always testing both userfaultfd(2) and /dev/userfaultfd,
> let the user choose which to test.
>
> As with other test features, change the behavior based on a new
> command line flag. Introduce the idea of "test mods", which are
> generic (not specific to a test type) modifications to the behavior of
> the test. This is sort of borrowed from this RFC patch series [1], but
> simplified a bit.
>
> The benefit is, in "typical" configurations this test is somewhat slow
> (say, 30sec or something). Testing both clearly doubles it, so it may
> not always be desirable, as users are likely to use one or the other,
> but never both, in the "real world".
>
> [1]: https://patchwork.kernel.org/project/linux-mm/patch/20201129004548.1619714-14-namit@vmware.com/
>
> Acked-by: Peter Xu <peterx@...hat.com>
> Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>
With a few nits below
Acked-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
> tools/testing/selftests/vm/userfaultfd.c | 69 ++++++++++++++++++++----
> 1 file changed, 60 insertions(+), 9 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 7c3f1b0ab468..cae72867c173 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -77,6 +77,11 @@ static int bounces;
> #define TEST_SHMEM 3
> static int test_type;
>
> +#define UFFD_FLAGS (O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY)
> +
> +/* test using /dev/userfaultfd, instead of userfaultfd(2) */
> +static bool test_dev_userfaultfd;
> +
> /* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
> #define ALARM_INTERVAL_SECS 10
> static volatile bool test_uffdio_copy_eexist = true;
> @@ -125,6 +130,8 @@ struct uffd_stats {
> const char *examples =
> "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
> "./userfaultfd anon 100 99999\n\n"
> + "# Run the same anonymous memory test, but using /dev/userfaultfd:\n"
> + "./userfaultfd anon:dev 100 99999\n\n"
> "# Run share memory test on 1GiB region with 99 bounces:\n"
> "./userfaultfd shmem 1000 99\n\n"
> "# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
> @@ -141,6 +148,14 @@ static void usage(void)
> "[hugetlbfs_file]\n\n");
> fprintf(stderr, "Supported <test type>: anon, hugetlb, "
> "hugetlb_shared, shmem\n\n");
> + fprintf(stderr, "'Test mods' can be joined to the test type string with a ':'. "
> + "Supported mods:\n");
> + fprintf(stderr, "\tsyscall - Use userfaultfd(2) (default)\n");
> + fprintf(stderr, "\tdev - Use /dev/userfaultfd instead of userfaultfd(2)\n");
> + fprintf(stderr, "\nExample test mod usage:\n");
> + fprintf(stderr, "# Run anonymous memory test with /dev/userfaultfd:\n");
> + fprintf(stderr, "./userfaultfd anon:dev 100 99999\n\n");
> +
> fprintf(stderr, "Examples:\n\n");
> fprintf(stderr, "%s", examples);
> exit(1);
> @@ -154,12 +169,14 @@ static void usage(void)
> ret, __LINE__); \
> } while (0)
>
> -#define err(fmt, ...) \
> +#define errexit(exitcode, fmt, ...) \
> do { \
> _err(fmt, ##__VA_ARGS__); \
> - exit(1); \
> + exit(exitcode); \
> } while (0)
>
> +#define err(fmt, ...) errexit(1, fmt, ##__VA_ARGS__)
> +
> static void uffd_stats_reset(struct uffd_stats *uffd_stats,
> unsigned long n_cpus)
> {
> @@ -383,13 +400,29 @@ static void assert_expected_ioctls_present(uint64_t mode, uint64_t ioctls)
> }
> }
>
> +static int __userfaultfd_open_dev(void)
> +{
> + int fd, _uffd = -1;
Nit: the initialization here is not necessary, _uffd is always set from
ioctl() return value.
> +
> + fd = open("/dev/userfaultfd", O_RDWR | O_CLOEXEC);
> + if (fd < 0)
> + return -1;
> +
> + _uffd = ioctl(fd, USERFAULTFD_IOC_NEW, UFFD_FLAGS);
> + close(fd);
> + return _uffd;
> +}
> +
> static void userfaultfd_open(uint64_t *features)
> {
> struct uffdio_api uffdio_api;
>
> - uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
> + if (test_dev_userfaultfd)
> + uffd = __userfaultfd_open_dev();
> + else
> + uffd = syscall(__NR_userfaultfd, UFFD_FLAGS);
> if (uffd < 0)
> - err("userfaultfd syscall not available in this kernel");
> + errexit(KSFT_SKIP, "creating userfaultfd failed");
I'm not sure if this should be KSFT_SKIP. If creation of uffd failed
because anything except ENOSYS I'd consider the test failing.
> uffd_flags = fcntl(uffd, F_GETFD, NULL);
>
> uffdio_api.api = UFFD_API;
> @@ -1584,8 +1617,6 @@ unsigned long default_huge_page_size(void)
>
> static void set_test_type(const char *type)
> {
> - uint64_t features = UFFD_API_FEATURES;
> -
> if (!strcmp(type, "anon")) {
> test_type = TEST_ANON;
> uffd_test_ops = &anon_uffd_test_ops;
> @@ -1603,9 +1634,29 @@ static void set_test_type(const char *type)
> test_type = TEST_SHMEM;
> uffd_test_ops = &shmem_uffd_test_ops;
> test_uffdio_minor = true;
> - } else {
> - err("Unknown test type: %s", type);
> }
> +}
> +
> +static void parse_test_type_arg(const char *raw_type)
> +{
> + char *buf = strdup(raw_type);
> + uint64_t features = UFFD_API_FEATURES;
> +
> + while (buf) {
> + const char *token = strsep(&buf, ":");
> +
> + if (!test_type)
> + set_test_type(token);
> + else if (!strcmp(token, "dev"))
> + test_dev_userfaultfd = true;
> + else if (!strcmp(token, "syscall"))
> + test_dev_userfaultfd = false;
> + else
> + err("unrecognized test mod '%s'", token);
> + }
> +
> + if (!test_type)
> + err("failed to parse test type argument: '%s'", raw_type);
>
> if (test_type == TEST_HUGETLB)
> page_size = default_huge_page_size();
> @@ -1653,7 +1704,7 @@ int main(int argc, char **argv)
> err("failed to arm SIGALRM");
> alarm(ALARM_INTERVAL_SECS);
>
> - set_test_type(argv[1]);
> + parse_test_type_arg(argv[1]);
>
> nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /
> --
> 2.37.1.559.g78731f0fdb-goog
>
--
Sincerely yours,
Mike.
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