selftests/mm: virtual_address_range: mmap() without PROT_WRITE

Patch series "selftests/mm: virtual_address_range: Reduce memory", v4.

The selftest started failing since commit e93d252 ("x86/vdso: Split
virtual clock pages into dedicated mapping") was merged.  While debugging
I stumbled upon some memory usage optimizations.

With these test now runs on a VM with only 60MiB of memory.


This patch (of 4):

When mapping a larger chunk than physical memory is available with
PROT_WRITE and overcommit is disabled, the mapping will fail.  This will
prevent the test from running on systems with less then ~1GiB of memory
and triggering an inscrutinable test failure.  As the mappings are never
written to anyways, the flag can be removed.

Link: https://lkml.kernel.org/r/20250114-virtual_address_range-tests-v4-0-6fd7269934a5@linutronix.de
Link: https://lkml.kernel.org/r/20250114-virtual_address_range-tests-v4-1-6fd7269934a5@linutronix.de
Fixes: 4e5ce33 ("selftests/vm: add a test for virtual address range mapping")
Signed-off-by: Thomas Weißschuh <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Acked-by: Dev Jain <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Shuah Khan (Samsung OSG) <[email protected]>
Cc: kernel test robot <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: t-8ch

tools/testing/selftests/mm/virtual_address_range.c

@@ -166,7 +166,7 @@ int main(int argc, char *argv[])
 	ksft_set_plan(1);
 
 	for (i = 0; i < NR_CHUNKS_LOW; i++) {
-		ptr[i] = mmap(NULL, MAP_CHUNK_SIZE, PROT_READ | PROT_WRITE,
+		ptr[i] = mmap(NULL, MAP_CHUNK_SIZE, PROT_READ,
 			      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
 		if (ptr[i] == MAP_FAILED) {
@@ -186,7 +186,7 @@ int main(int argc, char *argv[])
 
 	for (i = 0; i < NR_CHUNKS_HIGH; i++) {
 		hint = hint_addr();
-		hptr[i] = mmap(hint, MAP_CHUNK_SIZE, PROT_READ | PROT_WRITE,
+		hptr[i] = mmap(hint, MAP_CHUNK_SIZE, PROT_READ,
 			       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
 		if (hptr[i] == MAP_FAILED)