mm: no more EINVAL from /proc/sys/vm/stat_refresh

EINVAL was good for drawing the refresher's attention to a warning in
dmesg, but became very tiresome when running test suites scripted with
"set -e": an underflow from a bug in one feature would cause unrelated
tests much later to fail, just because their /proc/sys/vm/stat_refresh
touch failed with that error.  Stop doing that.

Link: https://lkml.kernel.org/r/alpine.LSU.2.11.2102251510410.13363@eggly.anvilsSigned-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/vmstat.c

@@ -1862,7 +1862,6 @@ int vmstat_refresh(struct ctl_table *table, int write,
 		if (val < 0) {
 			pr_warn("%s: %s %ld\n",
 				__func__, zone_stat_name(i), val);
-			err = -EINVAL;
 		}
 	}
 #ifdef CONFIG_NUMA
@@ -1871,7 +1870,6 @@ int vmstat_refresh(struct ctl_table *table, int write,
 		if (val < 0) {
 			pr_warn("%s: %s %ld\n",
 				__func__, numa_stat_name(i), val);
-			err = -EINVAL;
 		}
 	}
 #endif
@@ -1880,11 +1878,8 @@ int vmstat_refresh(struct ctl_table *table, int write,
 		if (val < 0) {
 			pr_warn("%s: %s %ld\n",
 				__func__, node_stat_name(i), val);
-			err = -EINVAL;
 		}
 	}
-	if (err)
-		return err;
 	if (write)
 		*ppos += *lenp;
 	else