[PATCH v6 13/14] selftests/vm: test flag is broken

Pavel Tatashin
2021-01-20T01:48:52Z

In gup_test both gup_flags and test_flags use the same flags field.
This is broken.

Farther, in the actual gup_test.c all the passed gup_flags are erased and
unconditionally replaced with FOLL_WRITE.

Which means that test_flags are ignored, and code like this always
performs pin dump test:

155 if (gup->flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
156 nr = pin_user_pages(addr, nr, gup->flags,
157 pages + i, NULL);
158 else
159 nr = get_user_pages(addr, nr, gup->flags,
160 pages + i, NULL);
161 break;

Add a new test_flags field, to allow raw gup_flags to work.
Add a new subcommand for DUMP_USER_PAGES_TEST to specify that pin test
should be performed.
Remove unconditional overwriting of gup_flags via FOLL_WRITE. But,
preserve the previous behaviour where FOLL_WRITE was the default flag,
and add a new option "-W" to unset FOLL_WRITE.

Rename flags with gup_flags.

With the fix, dump works like this:

root@virtme:/# gup_test -c
---- page #0, starting from user virt addr: 0x7f8acb9e4000
page:00000000d3d2ee27 refcount:2 mapcount:1 mapping:0000000000000000
index:0x0 pfn:0x100bcf
anon flags: 0x300000000080016(referenced|uptodate|lru|swapbacked)
raw: 0300000000080016 ffffd0e204021608 ffffd0e208df2e88 ffff8ea04243ec61
raw: 0000000000000000 0000000000000000 0000000200000000 0000000000000000
page dumped because: gup_test: dump_pages() test
DUMP_USER_PAGES_TEST: done

root@virtme:/# gup_test -c -p
---- page #0, starting from user virt addr: 0x7fd19701b000
page:00000000baed3c7d refcount:1025 mapcount:1 mapping:0000000000000000
index:0x0 pfn:0x108008
anon flags: 0x300000000080014(uptodate|lru|swapbacked)
raw: 0300000000080014 ffffd0e204200188 ffffd0e205e09088 ffff8ea04243ee71
raw: 0000000000000000 0000000000000000 0000040100000000 0000000000000000
page dumped because: gup_test: dump_pages() test
DUMP_USER_PAGES_TEST: done

Refcount shows the difference between pin vs no-pin case.
Also change type of nr from int to long, as it counts number of pages.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
---
mm/gup_test.c | 23 ++++++++++-------------
mm/gup_test.h | 3 ++-
tools/testing/selftests/vm/gup_test.c | 15 +++++++++++----
3 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/mm/gup_test.c b/mm/gup_test.c
index e3cf78e5873e..a6ed1c877679 100644
--- a/mm/gup_test.c
+++ b/mm/gup_test.c
@@ -94,7 +94,7 @@ static int __gup_test_ioctl(unsigned int cmd,
{
ktime_t start_time, end_time;
unsigned long i, nr_pages, addr, next;
- int nr;
+ long nr;
struct page **pages;
int ret = 0;
bool needs_mmap_lock =
@@ -126,37 +126,34 @@ static int __gup_test_ioctl(unsigned int cmd,
nr = (next - addr) / PAGE_SIZE;
}

- /* Filter out most gup flags: only allow a tiny subset here: */
- gup->flags &= FOLL_WRITE;
-
switch (cmd) {
case GUP_FAST_BENCHMARK:
- nr = get_user_pages_fast(addr, nr, gup->flags,
+ nr = get_user_pages_fast(addr, nr, gup->gup_flags,
pages + i);
break;
case GUP_BASIC_TEST:
- nr = get_user_pages(addr, nr, gup->flags, pages + i,
+ nr = get_user_pages(addr, nr, gup->gup_flags, pages + i,
NULL);
break;
case PIN_FAST_BENCHMARK:
- nr = pin_user_pages_fast(addr, nr, gup->flags,
+ nr = pin_user_pages_fast(addr, nr, gup->gup_flags,
pages + i);
break;
case PIN_BASIC_TEST:
- nr = pin_user_pages(addr, nr, gup->flags, pages + i,
+ nr = pin_user_pages(addr, nr, gup->gup_flags, pages + i,
NULL);
break;
case PIN_LONGTERM_BENCHMARK:
nr = pin_user_pages(addr, nr,
- gup->flags | FOLL_LONGTERM,
+ gup->gup_flags | FOLL_LONGTERM,
pages + i, NULL);
break;
case DUMP_USER_PAGES_TEST:
- if (gup->flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
- nr = pin_user_pages(addr, nr, gup->flags,
+ if (gup->test_flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
+ nr = pin_user_pages(addr, nr, gup->gup_flags,
pages + i, NULL);
else
- nr = get_user_pages(addr, nr, gup->flags,
+ nr = get_user_pages(addr, nr, gup->gup_flags,
pages + i, NULL);
break;
default:
@@ -187,7 +184,7 @@ static int __gup_test_ioctl(unsigned int cmd,

start_time = ktime_get();

- put_back_pages(cmd, pages, nr_pages, gup->flags);
+ put_back_pages(cmd, pages, nr_pages, gup->test_flags);

end_time = ktime_get();
gup->put_delta_usec = ktime_us_delta(end_time, start_time);
diff --git a/mm/gup_test.h b/mm/gup_test.h
index 90a6713d50eb..887ac1d5f5bc 100644
--- a/mm/gup_test.h
+++ b/mm/gup_test.h
@@ -21,7 +21,8 @@ struct gup_test {
__u64 addr;
__u64 size;
__u32 nr_pages_per_call;
- __u32 flags;
+ __u32 gup_flags;
+ __u32 test_flags;
/*
* Each non-zero entry is the number of the page (1-based: first page is
* page 1, so that zero entries mean "do nothing") from the .addr base.
diff --git a/tools/testing/selftests/vm/gup_test.c b/tools/testing/selftests/vm/gup_test.c
index 6c6336dd3b7f..943cc2608dc2 100644
--- a/tools/testing/selftests/vm/gup_test.c
+++ b/tools/testing/selftests/vm/gup_test.c
@@ -37,13 +37,13 @@ int main(int argc, char **argv)
{
struct gup_test gup = { 0 };
unsigned long size = 128 * MB;
- int i, fd, filed, opt, nr_pages = 1, thp = -1, repeats = 1, write = 0;
+ int i, fd, filed, opt, nr_pages = 1, thp = -1, repeats = 1, write = 1;
unsigned long cmd = GUP_FAST_BENCHMARK;
int flags = MAP_PRIVATE;
char *file = "/dev/zero";
char *p;

- while ((opt = getopt(argc, argv, "m:r:n:F:f:abctTLUuwSH")) != -1) {
+ while ((opt = getopt(argc, argv, "m:r:n:F:f:abctTLUuwWSHp")) != -1) {
switch (opt) {
case 'a':
cmd = PIN_FAST_BENCHMARK;
@@ -65,9 +65,13 @@ int main(int argc, char **argv)
*/
gup.which_pages[0] = 1;
break;
+ case 'p':
+ /* works only with DUMP_USER_PAGES_TEST */
+ gup.test_flags |= GUP_TEST_FLAG_DUMP_PAGES_USE_PIN;
+ break;
case 'F':
/* strtol, so you can pass flags in hex form */
- gup.flags = strtol(optarg, 0, 0);
+ gup.gup_flags = strtol(optarg, 0, 0);
break;
case 'm':
size = atoi(optarg) * MB;
@@ -93,6 +97,9 @@ int main(int argc, char **argv)
case 'w':
write = 1;
break;
+ case 'W':
+ write = 0;
+ break;
case 'f':
file = optarg;
break;
@@ -140,7 +147,7 @@ int main(int argc, char **argv)

gup.nr_pages_per_call = nr_pages;
if (write)
- gup.flags |= FOLL_WRITE;
+ gup.gup_flags |= FOLL_WRITE;

fd = open("/sys/kernel/debug/gup_test", O_RDWR);
if (fd == -1) {
--
2.25.1