selftests/mm: check that PAGEMAP_SCAN returns correct categories

Right now, tests read page flags from /proc/pid/pagemap files.  With this
change, tests will check that PAGEMAP_SCAN return correct information too.

[colin.i.king@gmail.com: fix spelling mistake "succedded" -> "succeeded"]
  Link: https://lkml.kernel.org/r/20231121093104.1728332-1-colin.i.king@gmail.com
Link: https://lkml.kernel.org/r/20231106220959.296568-2-avagin@google.comSigned-off-by: Andrei Vagin <avagin@google.com>
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Michał Mirosław <mirq-linux@rere.qmqm.pl>
[avagin@google.com: allow running tests on old kernels]
  Link: https://lkml.kernel.org/r/20231117181127.2574897-1-avagin@google.comSigned-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/mm/vm_util.c

@@ -4,6 +4,7 @@
 #include <dirent.h>
 #include <sys/ioctl.h>
 #include <linux/userfaultfd.h>
+#include <linux/fs.h>
 #include <sys/syscall.h>
 #include <unistd.h>
 #include "../kselftest.h"
@@ -28,19 +29,92 @@ uint64_t pagemap_get_entry(int fd, char *start)
 	return entry;
 }
 
+static uint64_t __pagemap_scan_get_categories(int fd, char *start, struct page_region *r)
+{
+	struct pm_scan_arg arg;
+
+	arg.start = (uintptr_t)start;
+	arg.end = (uintptr_t)(start + psize());
+	arg.vec = (uintptr_t)r;
+	arg.vec_len = 1;
+	arg.flags = 0;
+	arg.size = sizeof(struct pm_scan_arg);
+	arg.max_pages = 0;
+	arg.category_inverted = 0;
+	arg.category_mask = 0;
+	arg.category_anyof_mask = PAGE_IS_WPALLOWED | PAGE_IS_WRITTEN | PAGE_IS_FILE |
+				  PAGE_IS_PRESENT | PAGE_IS_SWAPPED | PAGE_IS_PFNZERO |
+				  PAGE_IS_HUGE | PAGE_IS_SOFT_DIRTY;
+	arg.return_mask = arg.category_anyof_mask;
+
+	return ioctl(fd, PAGEMAP_SCAN, &arg);
+}
+
+static uint64_t pagemap_scan_get_categories(int fd, char *start)
+{
+	struct page_region r;
+	long ret;
+
+	ret = __pagemap_scan_get_categories(fd, start, &r);
+	if (ret < 0)
+		ksft_exit_fail_msg("PAGEMAP_SCAN failed: %s\n", strerror(errno));
+	if (ret == 0)
+		return 0;
+	return r.categories;
+}
+
+/* `start` is any valid address. */
+static bool pagemap_scan_supported(int fd, char *start)
+{
+	static int supported = -1;
+	int ret;
+
+	if (supported != -1)
+		return supported;
+
+	/* Provide an invalid address in order to trigger EFAULT. */
+	ret = __pagemap_scan_get_categories(fd, start, (struct page_region *) ~0UL);
+	if (ret == 0)
+		ksft_exit_fail_msg("PAGEMAP_SCAN succeeded unexpectedly\n");
+
+	supported = errno == EFAULT;
+
+	return supported;
+}
+
+static bool page_entry_is(int fd, char *start, char *desc,
+			  uint64_t pagemap_flags, uint64_t pagescan_flags)
+{
+	bool m = pagemap_get_entry(fd, start) & pagemap_flags;
+
+	if (pagemap_scan_supported(fd, start)) {
+		bool s = pagemap_scan_get_categories(fd, start) & pagescan_flags;
+
+		if (m == s)
+			return m;
+
+		ksft_exit_fail_msg(
+			"read and ioctl return unmatched results for %s: %d %d", desc, m, s);
+	}
+	return m;
+}
+
 bool pagemap_is_softdirty(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & PM_SOFT_DIRTY;
+	return page_entry_is(fd, start, "soft-dirty",
+				PM_SOFT_DIRTY, PAGE_IS_SOFT_DIRTY);
 }
 
 bool pagemap_is_swapped(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & PM_SWAP;
+	return page_entry_is(fd, start, "swap", PM_SWAP, PAGE_IS_SWAPPED);
 }
 
 bool pagemap_is_populated(int fd, char *start)
 {
-	return pagemap_get_entry(fd, start) & (PM_PRESENT | PM_SWAP);
+	return page_entry_is(fd, start, "populated",
+				PM_PRESENT | PM_SWAP,
+				PAGE_IS_PRESENT | PAGE_IS_SWAPPED);
 }
 
 unsigned long pagemap_get_pfn(int fd, char *start)