Author: imp
Date: Wed Sep 20 21:19:53 2017
New Revision: 323829
URL: https://svnweb.freebsd.org/changeset/base/323829

Log:
  cam iosched: Add a handler for the quanta sysctl to enforce valid values
  
  Invalid values can result in devision-by-zero panics or other
  undefined behaviour so lets not allow them.
  
  PR: 221957
  Obtained from: ElectroBSD
  Submitted by: Fabian Keil
  Differential Revision: https://reviews.freebsd.org/D12351

Modified:
  head/sys/cam/cam_iosched.c

Modified: head/sys/cam/cam_iosched.c
==============================================================================
--- head/sys/cam/cam_iosched.c  Wed Sep 20 21:13:20 2017        (r323828)
+++ head/sys/cam/cam_iosched.c  Wed Sep 20 21:19:53 2017        (r323829)
@@ -883,6 +883,27 @@ cam_iosched_sysctl_latencies(SYSCTL_HANDLER_ARGS)
        return (error);
 }
 
+static int
+cam_iosched_quanta_sysctl(SYSCTL_HANDLER_ARGS)
+{
+       int *quanta;
+       int error, value;
+
+       quanta = (unsigned *)arg1;
+       value = *quanta;
+
+       error = sysctl_handle_int(oidp, (int *)&value, 0, req);
+       if ((error != 0) || (req->newptr == NULL))
+               return (error);
+
+       if (value < 1 || value > hz)
+               return (EINVAL);
+
+       *quanta = value;
+
+       return (0);
+}
+
 static void
 cam_iosched_iop_stats_sysctl_init(struct cam_iosched_softc *isc, struct 
iop_stats *ios, char *name)
 {
@@ -1104,9 +1125,9 @@ void cam_iosched_sysctl_init(struct cam_iosched_softc 
            &isc->read_bias, 100,
            "How biased towards read should we be independent of limits");
 
-       SYSCTL_ADD_INT(ctx, n,
-           OID_AUTO, "quanta", CTLFLAG_RW,
-           &isc->quanta, 200,
+       SYSCTL_ADD_PROC(ctx, n,
+           OID_AUTO, "quanta", CTLTYPE_UINT | CTLFLAG_RW,
+           &isc->quanta, 0, cam_iosched_quanta_sysctl, "I",
            "How many quanta per second do we slice the I/O up into");
 
        SYSCTL_ADD_INT(ctx, n,
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