mm/gup_test: fix PIN_LONGTERM_TEST_READ with highmem

Patch series "selftests/vm: fix some tests on 32bit".

I finally had the time to run some of the selftests written by me
(especially "cow") on x86 PAE.  I found some unexpected "surprises" :)

With these changes, and with [1] on top of mm-unstable, the "cow" tests
and the "ksm_functional_tests" compile and pass as expected (expected
failures with hugetlb in the "cow" tests).  "madv_populate" has one
expected test failure -- x86 does not support softdirty tracking.

#1-#3 fix commits with stable commit ids.  #4 fixes a test that is not in
mm-stable yet.

A note that there are many other compile errors/warnings when compiling on
32bit and with older Linux headers ...  something for another day.

[1] https://lkml.kernel.org/r/[email protected]


This patch (of 4):

...  we have to kmap()/kunmap(), otherwise this won't work as expected
with highmem.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: c77369b ("mm/gup_test: start/stop/read functionality for PIN LONGTERM test")
Signed-off-by: David Hildenbrand <[email protected]>
Cc: Shuah Khan <[email protected]>,
Cc: Yang Li <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: davidhildenbrand

mm/gup_test.c

@@ -4,6 +4,7 @@
 #include <linux/uaccess.h>
 #include <linux/ktime.h>
 #include <linux/debugfs.h>
+#include <linux/highmem.h>
 #include "gup_test.h"
 
 static void put_back_pages(unsigned int cmd, struct page **pages,
@@ -297,10 +298,13 @@ static inline int pin_longterm_test_read(unsigned long arg)
 		return -EFAULT;
 
 	for (i = 0; i < pin_longterm_test_nr_pages; i++) {
-		void *addr = page_to_virt(pin_longterm_test_pages[i]);
+		void *addr = kmap_local_page(pin_longterm_test_pages[i]);
+		unsigned long ret;
 
-		if (copy_to_user((void __user *)(unsigned long)user_addr, addr,
-				 PAGE_SIZE))
+		ret = copy_to_user((void __user *)(unsigned long)user_addr, addr,
+				   PAGE_SIZE);
+		kunmap_local(addr);
+		if (ret)
 			return -EFAULT;
 		user_addr += PAGE_SIZE;
 	}