Commit 97713a3a authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

selftests/vm: cow: R/O long-term pinning reliability tests for non-anon pages 

Let's test whether R/O long-term pinning is reliable for non-anonymous
memory: when R/O long-term pinning a page, the expectation is that we
break COW early before pinning, such that actual write access via the
page tables won't break COW later and end up replacing the R/O-pinned
page in the page table.

Consequently, R/O long-term pinning in private mappings would only target
exclusive anonymous pages.

For now, all tests fail:
	# [RUN] R/O longterm GUP pin ... with shared zeropage
	not ok 151 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with memfd
	not ok 152 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with tmpfile
	not ok 153 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with huge zeropage
	not ok 154 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with memfd hugetlb (2048 kB)
	not ok 155 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP pin ... with memfd hugetlb (1048576 kB)
	not ok 156 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with shared zeropage
	not ok 157 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with memfd
	not ok 158 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with tmpfile
	not ok 159 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with huge zeropage
	not ok 160 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (2048 kB)
	not ok 161 Longterm R/O pin is reliable
	# [RUN] R/O longterm GUP-fast pin ... with memfd hugetlb (1048576 kB)
	not ok 162 Longterm R/O pin is reliable

Link: https://lkml.kernel.org/r/20221116102659.70287-4-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f8664f3c

tools/testing/selftests/vm/cow.c

+27 −1
Original line number Original line Diff line number Diff line
@@ -561,6 +561,7 @@ static void test_iouring_fork(char *mem, size_t size) 
#endif /* LOCAL_CONFIG_HAVE_LIBURING */

#endif /* LOCAL_CONFIG_HAVE_LIBURING */





enum ro_pin_test {

enum ro_pin_test {

	RO_PIN_TEST,

	RO_PIN_TEST_SHARED,

	RO_PIN_TEST_SHARED,

	RO_PIN_TEST_PREVIOUSLY_SHARED,

	RO_PIN_TEST_PREVIOUSLY_SHARED,

	RO_PIN_TEST_RO_EXCLUSIVE,

	RO_PIN_TEST_RO_EXCLUSIVE,
@@ -593,6 +594,8 @@ static void do_test_ro_pin(char *mem, size_t size, enum ro_pin_test test, 
	}

	}





	switch (test) {

	switch (test) {

	case RO_PIN_TEST:

		break;

	case RO_PIN_TEST_SHARED:

	case RO_PIN_TEST_SHARED:

	case RO_PIN_TEST_PREVIOUSLY_SHARED:

	case RO_PIN_TEST_PREVIOUSLY_SHARED:

		/*

		/*
@@ -1193,6 +1196,16 @@ static void test_cow(char *mem, const char *smem, size_t size) 
	free(old);

	free(old);

}

}





static void test_ro_pin(char *mem, const char *smem, size_t size)

{

	do_test_ro_pin(mem, size, RO_PIN_TEST, false);

}



static void test_ro_fast_pin(char *mem, const char *smem, size_t size)

{

	do_test_ro_pin(mem, size, RO_PIN_TEST, true);

}



static void run_with_zeropage(non_anon_test_fn fn, const char *desc)

static void run_with_zeropage(non_anon_test_fn fn, const char *desc)

{

{

	char *mem, *smem, tmp;

	char *mem, *smem, tmp;
@@ -1433,7 +1446,7 @@ struct non_anon_test_case { 
};

};





/*

/*

 * Test cases that target any pages in private mappings that are non anonymous:

 * Test cases that target any pages in private mappings that are not anonymous:

 * pages that may get shared via COW ndependent of fork(). This includes

 * pages that may get shared via COW ndependent of fork(). This includes

 * the shared zeropage(s), pagecache pages, ...

 * the shared zeropage(s), pagecache pages, ...

 */

 */
@@ -1446,6 +1459,19 @@ static const struct non_anon_test_case non_anon_test_cases[] = { 
		"Basic COW",

		"Basic COW",

		test_cow,

		test_cow,

	},

	},

	/*

	 * Take a R/O longterm pin. When modifying the page via the page table,

	 * the page content change must be visible via the pin.

	 */

	{

		"R/O longterm GUP pin",

		test_ro_pin,

	},

	/* Same as above, but using GUP-fast. */

	{

		"R/O longterm GUP-fast pin",

		test_ro_fast_pin,

	},

};

};





static void run_non_anon_test_case(struct non_anon_test_case const *test_case)

static void run_non_anon_test_case(struct non_anon_test_case const *test_case)