Re: [PATCH v1 2/3] selftests/mm: gup_longterm: new functional test for FOLL_LONGTERM

From: Lorenzo Stoakes
Date: Sun May 28 2023 - 11:03:31 EST

Next message: Lorenzo Stoakes: "Re: [PATCH v1 3/3] selftests/mm: gup_longterm: add liburing tests"
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On Fri, May 19, 2023 at 12:27:22PM +0200, David Hildenbrand wrote:
> Let's add a new test for checking whether GUP long-term page pinning
> works as expected (R/O vs. R/W, MAP_PRIVATE vs. MAP_SHARED, GUP vs.
> GUP-fast). Note that COW handling with long-term R/O pinning in private
> mappings, and pinning of anonymous memory in general, is tested by the
> COW selftest. This test, therefore, focuses on page pinning in
> file mappings.
>
> The most interesting case is probably the "local tmpfile" case, as that
> will likely end up on a "real" filesystem such as ext4 or xfs, not on a
> virtual one like tmpfs or hugetlb where any long-term page pinning is
> always expected to succeed.
>
> For now, only add tests that use the "/sys/kernel/debug/gup_test"
> interface. We'll add tests based on liburing separately next.
>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
> tools/testing/selftests/mm/Makefile | 3 +
> tools/testing/selftests/mm/gup_longterm.c | 386 ++++++++++++++++++++++
> tools/testing/selftests/mm/run_vmtests.sh | 4 +-
> 3 files changed, 392 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/mm/gup_longterm.c
>
> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> index 23af4633f0f4..95acb099315e 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -34,6 +34,7 @@ LDLIBS = -lrt -lpthread
>
> TEST_GEN_PROGS = cow
> TEST_GEN_PROGS += compaction_test
> +TEST_GEN_PROGS += gup_longterm
> TEST_GEN_PROGS += gup_test
> TEST_GEN_PROGS += hmm-tests
> TEST_GEN_PROGS += hugetlb-madvise
> @@ -164,6 +165,8 @@ endif
> # IOURING_EXTRA_LIBS may get set in local_config.mk, or it may be left empty.
> $(OUTPUT)/cow: LDLIBS += $(IOURING_EXTRA_LIBS)
>
> +$(OUTPUT)/gup_longterm: LDLIBS += $(IOURING_EXTRA_LIBS)
> +
> $(OUTPUT)/mlock-random-test $(OUTPUT)/memfd_secret: LDLIBS += -lcap
>
> $(OUTPUT)/ksm_tests: LDLIBS += -lnuma
> diff --git a/tools/testing/selftests/mm/gup_longterm.c b/tools/testing/selftests/mm/gup_longterm.c
> new file mode 100644
> index 000000000000..44a3617fd423
> --- /dev/null
> +++ b/tools/testing/selftests/mm/gup_longterm.c
> @@ -0,0 +1,386 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * GUP long-term page pinning tests.
> + *
> + * Copyright 2023, Red Hat, Inc.
> + *
> + * Author(s): David Hildenbrand <david@xxxxxxxxxx>
> + */
> +#define _GNU_SOURCE
> +#include <stdlib.h>
> +#include <string.h>
> +#include <stdbool.h>
> +#include <stdint.h>
> +#include <unistd.h>
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <assert.h>
> +#include <sys/mman.h>
> +#include <sys/ioctl.h>
> +#include <sys/vfs.h>
> +#include <linux/magic.h>
> +#include <linux/memfd.h>
> +
> +#include "local_config.h"
> +
> +#include "../../../../mm/gup_test.h"
> +#include "../kselftest.h"
> +#include "vm_util.h"
> +
> +static size_t pagesize;
> +static int nr_hugetlbsizes;
> +static size_t hugetlbsizes[10];
> +static int gup_fd;
> +
> +static __fsword_t get_fs_type(int fd)
> +{
> + struct statfs fs;
> + int ret;
> +
> + do {
> + ret = fstatfs(fd, &fs);
> + } while (ret && errno == EINTR);
> +
> + return ret ? 0 : fs.f_type;
> +}
> +
> +static bool fs_is_unknown(__fsword_t fs_type)
> +{
> + /*
> + * We only support some filesystems in our tests when dealing with
> + * R/W long-term pinning. For these filesystems, we can be fairly sure
> + * whether they support it or not.
> + */
> + switch (fs_type) {
> + case TMPFS_MAGIC:
> + case HUGETLBFS_MAGIC:
> + case BTRFS_SUPER_MAGIC:
> + case EXT4_SUPER_MAGIC:
> + case XFS_SUPER_MAGIC:
> + return false;
> + default:
> + return true;
> + }
> +}
> +
> +static bool fs_supports_writable_longterm_pinning(__fsword_t fs_type)
> +{
> + assert(!fs_is_unknown(fs_type));
> + switch (fs_type) {
> + case TMPFS_MAGIC:
> + case HUGETLBFS_MAGIC:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> +enum test_type {
> + TEST_TYPE_RO,
> + TEST_TYPE_RO_FAST,
> + TEST_TYPE_RW,
> + TEST_TYPE_RW_FAST,
> +};
> +
> +static void do_test(int fd, size_t size, enum test_type type, bool shared)
> +{
> + __fsword_t fs_type = get_fs_type(fd);
> + bool should_work;
> + char *mem;
> + int ret;
> +
> + if (ftruncate(fd, size)) {
> + ksft_test_result_fail("ftruncate() failed\n");
> + return;
> + }
> +
> + if (fallocate(fd, 0, 0, size)) {
> + if (size == pagesize)
> + ksft_test_result_fail("fallocate() failed\n");
> + else
> + ksft_test_result_skip("need more free huge pages\n");
> + return;
> + }
> +
> + mem = mmap(NULL, size, PROT_READ | PROT_WRITE,
> + shared ? MAP_SHARED : MAP_PRIVATE, fd, 0);
> + if (mem == MAP_FAILED) {
> + if (size == pagesize || shared)
> + ksft_test_result_fail("mmap() failed\n");
> + else
> + ksft_test_result_skip("need more free huge pages\n");
> + return;
> + }
> +
> + /*
> + * Fault in the page writable such that GUP-fast can eventually pin
> + * it immediately.
> + */
> + memset(mem, 0, size);

Nitty but why not just MAP_POPULATE?

> +
> + switch (type) {
> + case TEST_TYPE_RO:
> + case TEST_TYPE_RO_FAST:
> + case TEST_TYPE_RW:
> + case TEST_TYPE_RW_FAST: {
> + struct pin_longterm_test args;
> + const bool fast = type == TEST_TYPE_RO_FAST ||
> + type == TEST_TYPE_RW_FAST;
+ const bool rw = type == TEST_TYPE_RW ||
> + type == TEST_TYPE_RW_FAST;
> +
> + if (gup_fd < 0) {
> + ksft_test_result_skip("gup_test not available\n");
> + break;
> + }
> +
> + if (rw && shared && fs_is_unknown(fs_type)) {
> + ksft_test_result_skip("Unknown filesystem\n");
> + return;
> + }
> + /*
> + * R/O pinning or pinning in a private mapping is always
> + * expected to work. Otherwise, we expect long-term R/W pinning
> + * to only succeed for special fielesystems.
> + */
> + should_work = !shared || !rw ||
> + fs_supports_writable_longterm_pinning(fs_type);
> +
> + args.addr = (__u64)(uintptr_t)mem;
> + args.size = size;
> + args.flags = fast ? PIN_LONGTERM_TEST_FLAG_USE_FAST : 0;
> + args.flags |= rw ? PIN_LONGTERM_TEST_FLAG_USE_WRITE : 0;
> + ret = ioctl(gup_fd, PIN_LONGTERM_TEST_START, &args);
> + if (ret && errno == EINVAL) {
> + ksft_test_result_skip("PIN_LONGTERM_TEST_START failed\n");
> + break;
> + } else if (ret && errno == EFAULT) {
> + ksft_test_result(!should_work, "Should have failed\n");
> + break;
> + } else if (ret) {
> + ksft_test_result_fail("PIN_LONGTERM_TEST_START failed\n");
> + break;
> + }
> +
> + if (ioctl(gup_fd, PIN_LONGTERM_TEST_STOP))
> + ksft_print_msg("[INFO] PIN_LONGTERM_TEST_STOP failed\n");
> +
> + /*
> + * TODO: if the kernel ever supports long-term R/W pinning on
> + * some previously unsupported filesystems, we might want to
> + * perform some additional tests for possible data corruptions.
> + */
> + ksft_test_result(should_work, "Should have worked\n");
> + break;
> + }
> + default:
> + assert(false);
> + }
> +
> + munmap(mem, size);
> +}
> +
> +typedef void (*test_fn)(int fd, size_t size);
> +
> +static void run_with_memfd(test_fn fn, const char *desc)
> +{
> + int fd;
> +
> + ksft_print_msg("[RUN] %s ... with memfd\n", desc);
> +
> + fd = memfd_create("test", 0);
> + if (fd < 0) {
> + ksft_test_result_fail("memfd_create() failed\n");
> + return;
> + }
> +
> + fn(fd, pagesize);
> + close(fd);
> +}
> +
> +static void run_with_tmpfile(test_fn fn, const char *desc)
> +{
> + FILE *file;
> + int fd;
> +
> + ksft_print_msg("[RUN] %s ... with tmpfile\n", desc);
> +
> + file = tmpfile();
> + if (!file) {
> + ksft_test_result_fail("tmpfile() failed\n");
> + return;
> + }
> +
> + fd = fileno(file);
> + if (fd < 0) {
> + ksft_test_result_fail("fileno() failed\n");
> + return;
> + }
> +
> + fn(fd, pagesize);
> + fclose(file);
> +}
> +
> +static void run_with_local_tmpfile(test_fn fn, const char *desc)
> +{
> + char filename[] = __FILE__"_tmpfile_XXXXXX";
> + int fd;
> +
> + ksft_print_msg("[RUN] %s ... with local tmpfile\n", desc);
> +
> + fd = mkstemp(filename);
> + if (fd < 0) {
> + ksft_test_result_fail("mkstemp() failed\n");
> + return;
> + }
> +
> + if (unlink(filename)) {
> + ksft_test_result_fail("unlink() failed\n");
> + goto close;
> + }
> +
> + fn(fd, pagesize);
> +close:
> + close(fd);
> +}
> +
> +static void run_with_memfd_hugetlb(test_fn fn, const char *desc,
> + size_t hugetlbsize)
> +{
> + int flags = MFD_HUGETLB;
> + int fd;
> +
> + ksft_print_msg("[RUN] %s ... with memfd hugetlb (%zu kB)\n", desc,
> + hugetlbsize / 1024);
> +
> + flags |= __builtin_ctzll(hugetlbsize) << MFD_HUGE_SHIFT;

Hm this feels a little cute :)

> +
> + fd = memfd_create("test", flags);
> + if (fd < 0) {
> + ksft_test_result_skip("memfd_create() failed\n");
> + return;
> + }
> +
> + fn(fd, hugetlbsize);
> + close(fd);
> +}
> +
> +struct test_case {
> + const char *desc;
> + test_fn fn;
> +};
> +
> +static void test_shared_rw_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RW, true);
> +}
> +
> +static void test_shared_rw_fast_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RW_FAST, true);
> +}
> +
> +static void test_shared_ro_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RO, true);
> +}
> +
> +static void test_shared_ro_fast_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RO_FAST, true);
> +}
> +
> +static void test_private_rw_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RW, false);
> +}
> +
> +static void test_private_rw_fast_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RW_FAST, false);
> +}
> +
> +static void test_private_ro_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RO, false);
> +}
> +
> +static void test_private_ro_fast_pin(int fd, size_t size)
> +{
> + do_test(fd, size, TEST_TYPE_RO_FAST, false);
> +}
> +
> +static const struct test_case test_cases[] = {
> + {
> + "R/W longterm GUP pin in MAP_SHARED file mapping",
> + test_shared_rw_pin,
> + },
> + {
> + "R/W longterm GUP-fast pin in MAP_SHARED file mapping",
> + test_shared_rw_fast_pin,
> + },
> + {
> + "R/O longterm GUP pin in MAP_SHARED file mapping",
> + test_shared_ro_pin,
> + },
> + {
> + "R/O longterm GUP-fast pin in MAP_SHARED file mapping",
> + test_shared_ro_fast_pin,
> + },
> + {
> + "R/W longterm GUP pin in MAP_PRIVATE file mapping",
> + test_private_rw_pin,
> + },
> + {
> + "R/W longterm GUP-fast pin in MAP_PRIVATE file mapping",
> + test_private_rw_fast_pin,
> + },
> + {
> + "R/O longterm GUP pin in MAP_PRIVATE file mapping",
> + test_private_ro_pin,
> + },
> + {
> + "R/O longterm GUP-fast pin in MAP_PRIVATE file mapping",
> + test_private_ro_fast_pin,
> + },
> +};
> +
> +static void run_test_case(struct test_case const *test_case)
> +{
> + int i;
> +
> + run_with_memfd(test_case->fn, test_case->desc);
> + run_with_tmpfile(test_case->fn, test_case->desc);
> + run_with_local_tmpfile(test_case->fn, test_case->desc);
> + for (i = 0; i < nr_hugetlbsizes; i++)
> + run_with_memfd_hugetlb(test_case->fn, test_case->desc,
> + hugetlbsizes[i]);
> +}
> +
> +static int tests_per_test_case(void)
> +{
> + return 3 + nr_hugetlbsizes;
> +}
> +
> +int main(int argc, char **argv)
> +{
> + int i, err;
> +
> + pagesize = getpagesize();
> + nr_hugetlbsizes = detect_hugetlb_page_sizes(hugetlbsizes,
> + ARRAY_SIZE(hugetlbsizes));
> +
> + ksft_print_header();
> + ksft_set_plan(ARRAY_SIZE(test_cases) * tests_per_test_case());
> +
> + gup_fd = open("/sys/kernel/debug/gup_test", O_RDWR);
> +
> + for (i = 0; i < ARRAY_SIZE(test_cases); i++)
> + run_test_case(&test_cases[i]);
> +
> + err = ksft_get_fail_cnt();
> + if (err)
> + ksft_exit_fail_msg("%d out of %d tests failed\n",
> + err, ksft_test_num());
> + return ksft_exit_pass();
> +}
> diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
> index 4893eb60d96d..b6b1eb6a8a6b 100644
> --- a/tools/testing/selftests/mm/run_vmtests.sh
> +++ b/tools/testing/selftests/mm/run_vmtests.sh
> @@ -24,7 +24,7 @@ separated by spaces:
> - mmap
> tests for mmap(2)
> - gup_test
> - tests for gup using gup_test interface
> + tests for gup

Super nitty again, but I'm guessing this means the CONFIG_GUP_TEST
interface, perhaps worth keeping?

> - userfaultfd
> tests for userfaultfd(2)
> - compaction
> @@ -196,6 +196,8 @@ CATEGORY="gup_test" run_test ./gup_test -a
> # Dump pages 0, 19, and 4096, using pin_user_pages:
> CATEGORY="gup_test" run_test ./gup_test -ct -F 0x1 0 19 0x1000
>
> +CATEGORY="gup_test" run_test ./gup_longterm
> +
> CATEGORY="userfaultfd" run_test ./uffd-unit-tests
> uffd_stress_bin=./uffd-stress
> CATEGORY="userfaultfd" run_test ${uffd_stress_bin} anon 20 16
> --
> 2.40.1
>

OK this patch is really nice + well implemented, I can only point out a
couple EXTREMELY nitty comments :) Thanks very much for adding a test for
this, it's super useful!

Therefore,

Reviewed-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>

Next message: Lorenzo Stoakes: "Re: [PATCH v1 3/3] selftests/mm: gup_longterm: add liburing tests"
Previous message: andy . shevchenko: "Re: [PATCH v2] pinctrl:sunplus: Add check for kmalloc"
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