Avoid too-low rlimit limit for pmdabpf

On older Linux kernels (pre 5.11) running multiple BPF applications
may exceed the locked pages limit (RLIMIT_MEMLOCK) imposed in pmdabpf
and prevent additional BPF applications from starting.  The pmdabpf
has been changed to remove any locked page limit to elimitate this
arbitrary limit interferring with BPF application startup.  This patch
is based on the proposed patch from Nathan Scott in the issue.

Resolves: #1915

src/pmdas/bpf/bpf.c

@@ -127,33 +127,19 @@ int bpf_printfn(enum libbpf_print_level level, const char *out, va_list ap)
     return 0;
 }
 
-#define WANT_MEM	(100LL*1024*1024)
 /**
- * setrlimit required for BPF loading ... try for WANT_MEM, but will
- * accept whatever we can get
+ * setrlimit required for BPF loading ... try for infinite memlocking
+ * as we have no idea how much we will really need (it depends on all
+ * loaded eBPF programs).
  */
 void bpf_setrlimit()
 {
-    struct rlimit	rnew;
-    int			ret;
-    ret = getrlimit(RLIMIT_MEMLOCK, &rnew);
-    if (ret < 0) {
-        pmNotifyErr(LOG_ERR, "bpf_setrlimit: getrlimit RMLIMIT_MEMLOCK failed: %s", pmErrStr(-errno));
-	return;
-    }
-    if (rnew.rlim_max == RLIM_INFINITY)
-	rnew.rlim_cur = rnew.rlim_max = WANT_MEM;
-    else if (rnew.rlim_max > WANT_MEM)
-	rnew.rlim_cur = rnew.rlim_max = WANT_MEM;
-    else {
-	rnew.rlim_cur = rnew.rlim_max;
-        pmNotifyErr(LOG_INFO, "bpf_setrlimit: setrlimit RMLIMIT_MEMLOCK %lld not %lld", (long long)rnew.rlim_cur, WANT_MEM);
-    }
-    ret = setrlimit(RLIMIT_MEMLOCK, &rnew);
-    if (ret == 0)
-        pmNotifyErr(LOG_INFO, "setrlimit RMLIMIT_MEMLOCK ok");
+    struct rlimit      rnew = { RLIM_INFINITY, RLIM_INFINITY };
+
+    if (setrlimit(RLIMIT_MEMLOCK, &rnew) == 0)
+        pmNotifyErr(LOG_INFO, "setrlimit RLIMIT_MEMLOCK ok");
     else
-        pmNotifyErr(LOG_ERR, "setrlimit RMLIMIT_MEMLOCK (%lld,%lld) failed: %s", (long long)rnew.rlim_cur, (long long)rnew.rlim_max, pmErrStr(-errno));
+        pmNotifyErr(LOG_ERR, "setrlimit RLIMIT_MEMLOCK (infinity) failed: %s", pmErrStr(-errno));
 }
 
 /**