selftests: vm: check numa_available() before operating "merge_across_nodes" in ksm_tests

Patch series "selftests: vm: a few fixup patches".

This series contains three fixup patches for vm selftests.  They are
independent.  Please see the patches.


This patch (of 3):

Currently, ksm_tests operates "merge_across_nodes" with NUMA either
enabled or disabled.  In a system with NUMA disabled, these operations
will fail and output a misleading report given "merge_across_nodes" does
not exist in sysfs:

  ----------------------------
  running ./ksm_tests -M -p 10
  ----------------------------
  f /sys/kernel/mm/ksm/merge_across_nodes
  fopen: No such file or directory
  Cannot save default tunables
  [FAIL]
  ----------------------

So check numa_available() before those operations to skip them if NUMA is
disabled.

Link: https://lkml.kernel.org/r/20220521083825.319654-1-patrick.wang.shcn@gmail.com
Link: https://lkml.kernel.org/r/20220521083825.319654-2-patrick.wang.shcn@gmail.comSigned-off-by: Patrick Wang <patrick.wang.shcn@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/vm/ksm_tests.c

@@ -221,7 +221,8 @@ static bool assert_ksm_pages_count(long dupl_page_count)
 static int ksm_save_def(struct ksm_sysfs *ksm_sysfs)
 {
 	if (ksm_read_sysfs(KSM_FP("max_page_sharing"), &ksm_sysfs->max_page_sharing) ||
-	    ksm_read_sysfs(KSM_FP("merge_across_nodes"), &ksm_sysfs->merge_across_nodes) ||
+	    numa_available() ? 0 :
+		ksm_read_sysfs(KSM_FP("merge_across_nodes"), &ksm_sysfs->merge_across_nodes) ||
 	    ksm_read_sysfs(KSM_FP("sleep_millisecs"), &ksm_sysfs->sleep_millisecs) ||
 	    ksm_read_sysfs(KSM_FP("pages_to_scan"), &ksm_sysfs->pages_to_scan) ||
 	    ksm_read_sysfs(KSM_FP("run"), &ksm_sysfs->run) ||
@@ -236,7 +237,8 @@ static int ksm_save_def(struct ksm_sysfs *ksm_sysfs)
 static int ksm_restore(struct ksm_sysfs *ksm_sysfs)
 {
 	if (ksm_write_sysfs(KSM_FP("max_page_sharing"), ksm_sysfs->max_page_sharing) ||
-	    ksm_write_sysfs(KSM_FP("merge_across_nodes"), ksm_sysfs->merge_across_nodes) ||
+	    numa_available() ? 0 :
+		ksm_write_sysfs(KSM_FP("merge_across_nodes"), ksm_sysfs->merge_across_nodes) ||
 	    ksm_write_sysfs(KSM_FP("pages_to_scan"), ksm_sysfs->pages_to_scan) ||
 	    ksm_write_sysfs(KSM_FP("run"), ksm_sysfs->run) ||
 	    ksm_write_sysfs(KSM_FP("sleep_millisecs"), ksm_sysfs->sleep_millisecs) ||
@@ -720,7 +722,8 @@ int main(int argc, char *argv[])
 
 	if (ksm_write_sysfs(KSM_FP("run"), 2) ||
 	    ksm_write_sysfs(KSM_FP("sleep_millisecs"), 0) ||
-	    ksm_write_sysfs(KSM_FP("merge_across_nodes"), 1) ||
+	    numa_available() ? 0 :
+		ksm_write_sysfs(KSM_FP("merge_across_nodes"), 1) ||
 	    ksm_write_sysfs(KSM_FP("pages_to_scan"), page_count))
 		return KSFT_FAIL;