[PATCH RFC 5/5] mm/gup_test: Verify GUP grabs same pages twice

Elliot Berman
2024-06-19T00:05:33Z

GUP'ing pages should get the same pages, test it. In case of
FOLL_EXCLUSIVE, the second pin should fail to get any pages.

Note: this change ought to be refactored to pull out the GUP'ing bits
that's duplicated between the original and the second GUP.

Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>
---
mm/gup_test.c | 86 +++++++++++++++++++++++++++++++++++
mm/gup_test.h | 1 +
tools/testing/selftests/mm/gup_test.c | 5 +-
3 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/mm/gup_test.c b/mm/gup_test.c
index 9c6b8c93e44a7..28cc422b60b78 100644
--- a/mm/gup_test.c
+++ b/mm/gup_test.c
@@ -86,6 +86,89 @@ static void verify_exclusive_pinned(unsigned int gup_flags, struct page **pages,
}
}

+static int verify_gup_twice(unsigned int cmd, struct gup_test *gup,
+ struct page **expected_pages,
+ unsigned long expected_nr_pages)
+{
+ unsigned long i, nr_pages, addr, next;
+ long nr;
+ struct page **pages __free(kfree) = NULL;
+ int ret = 0;
+
+ nr_pages = gup->size / PAGE_SIZE;
+ pages = kvcalloc(nr_pages, sizeof(void *), GFP_KERNEL);
+ if (!pages)
+ return -ENOMEM;
+
+ i = 0;
+ nr = gup->nr_pages_per_call;
+ for (addr = gup->addr; addr < gup->addr + gup->size; addr = next) {
+ if (nr != gup->nr_pages_per_call)
+ break;
+
+ next = addr + nr * PAGE_SIZE;
+ if (next > gup->addr + gup->size) {
+ next = gup->addr + gup->size;
+ nr = (next - addr) / PAGE_SIZE;
+ }
+
+ switch (cmd) {
+ case GUP_FAST_BENCHMARK:
+ nr = get_user_pages_fast(addr, nr, gup->gup_flags,
+ pages + i);
+ break;
+ case GUP_BASIC_TEST:
+ nr = get_user_pages(addr, nr, gup->gup_flags, pages + i);
+ break;
+ case PIN_FAST_BENCHMARK:
+ nr = pin_user_pages_fast(addr, nr, gup->gup_flags,
+ pages + i);
+ break;
+ case PIN_BASIC_TEST:
+ nr = pin_user_pages(addr, nr, gup->gup_flags, pages + i);
+ break;
+ case PIN_LONGTERM_BENCHMARK:
+ nr = pin_user_pages(addr, nr,
+ gup->gup_flags | FOLL_LONGTERM,
+ pages + i);
+ break;
+ default:
+ pr_err("cmd %d not supported for %s\n", cmd, __func__);
+ return -EINVAL;
+ }
+
+ if (nr <= 0)
+ break;
+ i += nr;
+ }
+
+ nr_pages = i;
+
+ if (gup->gup_flags & FOLL_EXCLUSIVE) {
+ if (WARN(nr_pages,
+ "Able to acquire exclusive pin twice for %ld of %ld pages",
+ nr_pages, expected_nr_pages)) {
+ dump_page(pages[0],
+ "gup_test: verify_gup_twice() test");
+ ret = -EIO;
+ }
+ } else if (nr_pages != expected_nr_pages) {
+ pr_err("%s: Expected %ld pages, got %ld\n", __func__,
+ expected_nr_pages, nr_pages);
+ ret = -EIO;
+ } else {
+ for (i = 0; i < nr_pages; i++) {
+ if (WARN(pages[i] != expected_pages[i],
+ "pages[%lu] mismatch\n", i))
+ break;
+ }
+ }
+
+ put_back_pages(cmd, pages, nr_pages, gup->test_flags);
+
+ return ret;
+}
+
static void dump_pages_test(struct gup_test *gup, struct page **pages,
unsigned long nr_pages)
{
@@ -210,6 +293,9 @@ static int __gup_test_ioctl(unsigned int cmd,
if (cmd == DUMP_USER_PAGES_TEST)
dump_pages_test(gup, pages, nr_pages);

+ if (gup->test_flags & GUP_TEST_FLAG_GUP_TWICE)
+ ret = verify_gup_twice(cmd, gup, pages, nr_pages);
+
start_time = ktime_get();

put_back_pages(cmd, pages, nr_pages, gup->test_flags);
diff --git a/mm/gup_test.h b/mm/gup_test.h
index 5b37b54e8bea6..fcd41919b0159 100644
--- a/mm/gup_test.h
+++ b/mm/gup_test.h
@@ -17,6 +17,7 @@
#define GUP_TEST_MAX_PAGES_TO_DUMP 8

#define GUP_TEST_FLAG_DUMP_PAGES_USE_PIN 0x1
+#define GUP_TEST_FLAG_GUP_TWICE 0x2

struct gup_test {
__u64 get_delta_usec;
diff --git a/tools/testing/selftests/mm/gup_test.c b/tools/testing/selftests/mm/gup_test.c
index bdeaac67ff9aa..b4b10c8338f80 100644
--- a/tools/testing/selftests/mm/gup_test.c
+++ b/tools/testing/selftests/mm/gup_test.c
@@ -98,7 +98,7 @@ int main(int argc, char **argv)
pthread_t *tid;
char *p;

- while ((opt = getopt(argc, argv, "m:r:n:F:f:abcj:tTLUuwWSHpz")) != -1) {
+ while ((opt = getopt(argc, argv, "m:r:n:F:f:abcj:dtTLUuwWSHpz")) != -1) {
switch (opt) {
case 'a':
cmd = PIN_FAST_BENCHMARK;
@@ -172,6 +172,9 @@ int main(int argc, char **argv)
/* fault pages in gup, do not fault in userland */
touch = 1;
break;
+ case 'd':
+ gup.test_flags |= GUP_TEST_FLAG_GUP_TWICE;
+ break;
default:
ksft_exit_fail_msg("Wrong argument\n");
}

--
2.34.1