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@redhat.com --- 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@redhat.com + */ +#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); + + 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; + + 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 - 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

On Fri, May 19, 2023 at 12:27:21PM +0200, David Hildenbrand wrote:

Let's factor detection out into vm_util, to be reused by a new test.

Bit of a nit as it's hardly vitally important, but perhaps worth mentioning that you also refactor the function to accept any array (this is a requirement rather than simply refactoring a thing but still :)

Signed-off-by: David Hildenbrand david@redhat.com

tools/testing/selftests/mm/cow.c | 29 ++-------------------------- tools/testing/selftests/mm/vm_util.c | 27 ++++++++++++++++++++++++++ tools/testing/selftests/mm/vm_util.h | 1 + 3 files changed, 30 insertions(+), 27 deletions(-)

diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c index dc9d6fe86028..7f3b620d9cb7 100644 --- a/tools/testing/selftests/mm/cow.c +++ b/tools/testing/selftests/mm/cow.c @@ -14,7 +14,6 @@ #include <unistd.h> #include <errno.h> #include <fcntl.h> -#include <dirent.h> #include <assert.h> #include <sys/mman.h> #include <sys/ioctl.h> @@ -70,31 +69,6 @@ static void detect_huge_zeropage(void) close(fd); }

-static void detect_hugetlbsizes(void) -{

• DIR *dir = opendir("/sys/kernel/mm/hugepages/");
• if (!dir)

• return;
  

• while (nr_hugetlbsizes < ARRAY_SIZE(hugetlbsizes)) {

• struct dirent *entry = readdir(dir);
  

• size_t kb;
  

• if (!entry)
  

• 	break;
  

• if (entry->d_type != DT_DIR)
  

• 	continue;
  

• if (sscanf(entry->d_name, "hugepages-%zukB", &kb) != 1)
  

• 	continue;
  

• hugetlbsizes[nr_hugetlbsizes] = kb * 1024;
  

• nr_hugetlbsizes++;
  

• ksft_print_msg("[INFO] detected hugetlb size: %zu KiB\n",
  

• 	       kb);
  

• }
• closedir(dir);

-}

static bool range_is_swapped(void *addr, size_t size) { for (; size; addr += pagesize, size -= pagesize) @@ -1717,7 +1691,8 @@ int main(int argc, char **argv) if (thpsize) ksft_print_msg("[INFO] detected THP size: %zu KiB\n", thpsize / 1024);

• detect_hugetlbsizes();

• nr_hugetlbsizes = detect_hugetlb_page_sizes(hugetlbsizes,

• 				    ARRAY_SIZE(hugetlbsizes));
  

  detect_huge_zeropage();

  ksft_print_header();

diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c index 9b06a5034808..5cf84d860076 100644 --- a/tools/testing/selftests/mm/vm_util.c +++ b/tools/testing/selftests/mm/vm_util.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 #include <string.h> #include <fcntl.h> +#include <dirent.h> #include <sys/ioctl.h> #include <linux/userfaultfd.h> #include <sys/syscall.h> @@ -198,6 +199,32 @@ unsigned long default_huge_page_size(void) return hps; }

+int detect_hugetlb_page_sizes(size_t sizes[], int max) +{

• DIR *dir = opendir("/sys/kernel/mm/hugepages/");
• int count = 0;
• if (!dir)

• return 0;
  

• while (count < max) {

• struct dirent *entry = readdir(dir);
  

• size_t kb;
  

• if (!entry)
  

• 	break;
  

• if (entry->d_type != DT_DIR)
  

• 	continue;
  

• if (sscanf(entry->d_name, "hugepages-%zukB", &kb) != 1)
  

• 	continue;
  

• sizes[count++] = kb * 1024;
  

• ksft_print_msg("[INFO] detected hugetlb page size: %zu KiB\n",
  

• 	       kb);
  

• }
• closedir(dir);
• return count;

+}

/* If `ioctls' non-NULL, the allowed ioctls will be returned into the var */ int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len, bool miss, bool wp, bool minor, uint64_t *ioctls) diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h index b950bd16083a..99b795528716 100644 --- a/tools/testing/selftests/mm/vm_util.h +++ b/tools/testing/selftests/mm/vm_util.h @@ -44,6 +44,7 @@ bool check_huge_file(void *addr, int nr_hpages, uint64_t hpage_size); bool check_huge_shmem(void *addr, int nr_hpages, uint64_t hpage_size); int64_t allocate_transhuge(void *ptr, int pagemap_fd); unsigned long default_huge_page_size(void); +int detect_hugetlb_page_sizes(size_t sizes[], int max);

int uffd_register(int uffd, void *addr, uint64_t len, bool miss, bool wp, bool minor); -- 2.40.1

Looks good to me,

Reviewed-by: Lorenzo Stoakes lstoakes@gmail.com

On Fri, May 19, 2023 at 12:27:23PM +0200, David Hildenbrand wrote:

Similar to the COW selftests, also use io_uring fixed buffers to test if long-term page pinning works as expected.

Signed-off-by: David Hildenbrand david@redhat.com

tools/testing/selftests/mm/gup_longterm.c | 73 +++++++++++++++++++++++ 1 file changed, 73 insertions(+)

diff --git a/tools/testing/selftests/mm/gup_longterm.c b/tools/testing/selftests/mm/gup_longterm.c index 44a3617fd423..d33d3e68ffab 100644 --- a/tools/testing/selftests/mm/gup_longterm.c +++ b/tools/testing/selftests/mm/gup_longterm.c @@ -22,6 +22,9 @@ #include <linux/memfd.h>

#include "local_config.h" +#ifdef LOCAL_CONFIG_HAVE_LIBURING +#include <liburing.h> +#endif /* LOCAL_CONFIG_HAVE_LIBURING */

#include "../../../../mm/gup_test.h" #include "../kselftest.h" @@ -80,6 +83,9 @@ enum test_type { TEST_TYPE_RO_FAST, TEST_TYPE_RW, TEST_TYPE_RW_FAST, +#ifdef LOCAL_CONFIG_HAVE_LIBURING

• TEST_TYPE_IOURING,

+#endif /* LOCAL_CONFIG_HAVE_LIBURING */ };

static void do_test(int fd, size_t size, enum test_type type, bool shared) @@ -173,6 +179,51 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared) ksft_test_result(should_work, "Should have worked\n"); break; } +#ifdef LOCAL_CONFIG_HAVE_LIBURING

• case TEST_TYPE_IOURING: {

• struct io_uring ring;
  

• struct iovec iov;
  

• /* io_uring always pins pages writable. */
  

• if (shared && fs_is_unknown(fs_type)) {
  

• 	ksft_test_result_skip("Unknown filesystem\n");
  

• 	return;
  

• }
  

• should_work = !shared ||
  

• 	      fs_supports_writable_longterm_pinning(fs_type);
  

• /* Skip on errors, as we might just lack kernel support. */
  

• ret = io_uring_queue_init(1, &ring, 0);
  

• if (ret < 0) {
  

• 	ksft_test_result_skip("io_uring_queue_init() failed\n");
  

• 	break;
  

• }
  

• /*
  

•  * Register the range as a fixed buffer. This will FOLL_WRITE |
  

•  * FOLL_PIN | FOLL_LONGTERM the range.
  

•  */
  

• iov.iov_base = mem;
  

• iov.iov_len = size;
  

• ret = io_uring_register_buffers(&ring, &iov, 1);
  

• /* Only new kernels return EFAULT. */
  

• if (ret && (errno == ENOSPC || errno == EOPNOTSUPP ||
  

• 	    errno == EFAULT)) {
  

• 	ksft_test_result(!should_work, "Should have failed\n");
  

• } else if (ret) {
  

• 	/*
  

• 	 * We might just lack support or have insufficient
  

• 	 * MEMLOCK limits.
  

• 	 */
  

• 	ksft_test_result_skip("io_uring_register_buffers() failed\n");
  

• } else {
  

• 	ksft_test_result(should_work, "Should have worked\n");
  

• 	io_uring_unregister_buffers(&ring);
  

• }
  

• io_uring_queue_exit(&ring);
  

• break;
  

• }

+#endif /* LOCAL_CONFIG_HAVE_LIBURING */ default: assert(false); } @@ -310,6 +361,18 @@ static void test_private_ro_fast_pin(int fd, size_t size) do_test(fd, size, TEST_TYPE_RO_FAST, false); }

+#ifdef LOCAL_CONFIG_HAVE_LIBURING +static void test_shared_iouring(int fd, size_t size) +{

• do_test(fd, size, TEST_TYPE_IOURING, true);

+}

+static void test_private_iouring(int fd, size_t size) +{

• do_test(fd, size, TEST_TYPE_IOURING, false);

+} +#endif /* LOCAL_CONFIG_HAVE_LIBURING */

static const struct test_case test_cases[] = { { "R/W longterm GUP pin in MAP_SHARED file mapping", @@ -343,6 +406,16 @@ static const struct test_case test_cases[] = { "R/O longterm GUP-fast pin in MAP_PRIVATE file mapping", test_private_ro_fast_pin, }, +#ifdef LOCAL_CONFIG_HAVE_LIBURING

• {

• "io_uring fixed buffer with MAP_SHARED file mapping",
  

• test_shared_iouring,
  

• },
• {

• "io_uring fixed buffer with MAP_PRIVATE file mapping",
  

• test_private_iouring,
  

• },

+#endif /* LOCAL_CONFIG_HAVE_LIBURING */ };

static void run_test_case(struct test_case const *test_case)

2.40.1

All good,

Reviewed-by: Lorenzo Stoakes lstoakes@gmail.com

On 28.05.23 17:03, Lorenzo Stoakes wrote:

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@redhat.com

[...]

...

+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);

For shared mappings, MAP_POPULATE will not fault-in the pages writable. See mm/gup.c:populate_vma_page_range().

[There is also the case that mmap() doesn't fail if populate fails, but that's only a side note regarding weird semantics of MAP_POPULATE]

[...]

...

• 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 :)

It's a weird interfacing, having to specify the desired size via flags ... see the man page of memfd_create, which links to the man page of mmap: "the desired huge page size can be configured by encoding the base-2 logarithm of the desired page size in the six bits at the offset MAP_HUGE_SHIFT".

FWIW, we're using the same approach in cow.c already [and other memfd users like QEMU do it just like that, using ctz].

[...]

...

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?

With this patch, agreed. But not longer with the next patch -- guess I simplified when splitting it up. If there are no strong feelings I'll leave it in this patch.

[...]

...

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@gmail.com

Thanks for the review! My selftest patches rarely get that much attention, so highly appreciated :)

On 5/19/23 03:27, David Hildenbrand wrote: ...

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

Hi David,

Peter Xu just pointed out that we need a .gitignore entry for gup_longterm [1]. That logically belongs in this patch, I think.

[1] https://lore.kernel.org/all/ZH4FFa4FV9KGwBZo@x1n

thanks,

On Tue, 6 Jun 2023 09:10:22 +0200 David Hildenbrand david@redhat.com wrote:

On 06.06.23 08:23, John Hubbard wrote:

...

On 5/19/23 03:27, David Hildenbrand wrote: ...

...

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

Hi David,

Peter Xu just pointed out that we need a .gitignore entry for gup_longterm [1]. That logically belongs in this patch, I think.

Yes, although I don't care if it's in a follow-up patch (we're talking testcases after all).

@Andrew can you include that hunk in that patch or do you want a resend?

I added this:

From: Andrew Morton akpm@linux-foundation.org Subject: selftests-mm-gup_longterm-new-functional-test-for-foll_longterm-fix Date: Tue Jun 6 07:41:28 PM PDT 2023

update .gitignore for gup_longterm, per Peter

Cc: David Hildenbrand david@redhat.com Cc: Jan Kara jack@suse.cz Cc: Jason Gunthorpe jgg@nvidia.com Cc: Jens Axboe axboe@kernel.dk Cc: John Hubbard jhubbard@nvidia.com Cc: Lorenzo Stoakes lstoakes@gmail.com Cc: Peter Xu peterx@redhat.com Cc: Shuah Khan shuah@kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

tools/testing/selftests/mm/.gitignore | 1 + 1 file changed, 1 insertion(+)

--- a/tools/testing/selftests/mm/.gitignore~selftests-mm-gup_longterm-new-functional-test-for-foll_longterm-fix +++ a/tools/testing/selftests/mm/.gitignore @@ -39,3 +39,4 @@ local_config.h local_config.mk ksm_functional_tests mdwe_test +gup_longterm _