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From:   Pavel Tatashin <pasha.tatashin@soleen.com>
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        linux-kselftest@vger.kernel.org
Subject: [PATCH v4 09/10] selftests/vm: test flag is broken
Date:   Thu, 17 Dec 2020 13:52:42 -0500
Message-Id: <20201217185243.3288048-10-pasha.tatashin@soleen.com>
In-Reply-To: <20201217185243.3288048-1-pasha.tatashin@soleen.com>
References: <20201217185243.3288048-1-pasha.tatashin@soleen.com>
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In gup_test both gup_flags and test_flags use the same flags field.
This is broken, because gup_flags can be passed as raw value (via -F hex),
which can overwrite all the test flags.

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.

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                         |  9 +++------
 mm/gup_test.h                         |  1 +
 tools/testing/selftests/vm/gup_test.c | 11 +++++++++--
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/mm/gup_test.c b/mm/gup_test.c
index e3cf78e5873e..24c70c5814ba 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 =
@@ -126,9 +126,6 @@ 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,
@@ -152,7 +149,7 @@ static int __gup_test_ioctl(unsigned int cmd,
 					    pages + i, NULL);
 			break;
 		case DUMP_USER_PAGES_TEST:
-			if (gup->flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
+			if (gup->test_flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
 				nr = pin_user_pages(addr, nr, gup->flags,
 						    pages + i, NULL);
 			else
@@ -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..b1b376b5d3b2 100644
--- a/mm/gup_test.h
+++ b/mm/gup_test.h
@@ -22,6 +22,7 @@ struct gup_test {
 	__u64 size;
 	__u32 nr_pages_per_call;
 	__u32 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..42c71483729f 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;
@@ -65,6 +65,10 @@ 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);
@@ -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;
-- 
2.25.1