staging: unisys: visornic - consolidate+simplify xmit watermark checks

The code that tests for high and low xmit watermarks was consolidatedand
simplified. The output behavior should be identical, with the exception
of an off-by-one error being corrected in the tests done when the counters
overflowed.

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/unisys/visornic/visornic_main.c b/drivers/staging/unisys/visornic/visornic_main.c
index 14563afb3c70b660079b8d13f63a9ccfaa9f4901..7d4602973bbb5d1b8dd7f0be3d8ea3e47dadf7a9 100644 (file)
--- a/drivers/staging/unisys/visornic/visornic_main.c
+++ b/drivers/staging/unisys/visornic/visornic_main.c
@@ -135,15 +135,16 @@ struct visornic_devdata {
        atomic_t num_rcvbuf_in_iovm;
        unsigned long alloc_failed_in_if_needed_cnt;
        unsigned long alloc_failed_in_repost_rtn_cnt;
-       int max_outstanding_net_xmits;   /* absolute max number of outstanding
-                                         * xmits - should never hit this
-                                         */
-       int upper_threshold_net_xmits;   /* high water mark for calling
-                                         * netif_stop_queue()
-                                         */
-       int lower_threshold_net_xmits;   /* high water mark for calling
-                                         * netif_wake_queue()
-                                         */
+       unsigned long max_outstanding_net_xmits; /* absolute max number of
+                                                 * outstanding xmits - should
+                                                 * never hit this
+                                                 */
+       unsigned long upper_threshold_net_xmits;  /* high water mark for
+                                                  * calling netif_stop_queue()
+                                                  */
+       unsigned long lower_threshold_net_xmits; /* high water mark for calling
+                                                 * netif_wake_queue()
+                                                 */
        struct sk_buff_head xmitbufhead; /* xmitbufhead is the head of the
                                          * xmit buffer list that have been
                                          * sent to the IOPART end
@@ -794,6 +795,53 @@ visornic_close(struct net_device *netdev)
        return 0;
 }
 
+/**
+ *     devdata_xmits_outstanding - compute outstanding xmits
+ *     @devdata: visornic_devdata for device
+ *
+ *     Return value is the number of outstanding xmits.
+ */
+static unsigned long devdata_xmits_outstanding(struct visornic_devdata *devdata)
+{
+       if (devdata->chstat.sent_xmit >= devdata->chstat.got_xmit_done)
+               return devdata->chstat.sent_xmit -
+                       devdata->chstat.got_xmit_done;
+       else
+               return (ULONG_MAX - devdata->chstat.got_xmit_done
+                       + devdata->chstat.sent_xmit + 1);
+}
+
+/**
+ *     vnic_hit_high_watermark
+ *     @devdata: indicates visornic device we are checking
+ *     @high_watermark: max num of unacked xmits we will tolerate,
+ *                       before we will start throttling
+ *
+ *      Returns true iff the number of unacked xmits sent to
+ *      the IO partition is >= high_watermark.
+ */
+static inline bool vnic_hit_high_watermark(struct visornic_devdata *devdata,
+                                          ulong high_watermark)
+{
+       return (devdata_xmits_outstanding(devdata) >= high_watermark);
+}
+
+/**
+ *     vnic_hit_low_watermark
+ *     @devdata: indicates visornic device we are checking
+ *     @low_watermark: we will wait until the num of unacked xmits
+ *                      drops to this value or lower before we start
+ *                      transmitting again
+ *
+ *      Returns true iff the number of unacked xmits sent to
+ *      the IO partition is <= low_watermark.
+ */
+static inline bool vnic_hit_low_watermark(struct visornic_devdata *devdata,
+                                         ulong low_watermark)
+{
+       return (devdata_xmits_outstanding(devdata) <= low_watermark);
+}
+
 /**
  *     visornic_xmit - send a packet to the IO Partition
  *     @skb: Packet to be sent
@@ -869,13 +917,8 @@ visornic_xmit(struct sk_buff *skb, struct net_device *netdev)
        /* save the pointer to skb -- we'll need it for completion */
        cmdrsp->net.buf = skb;
 
-       if (((devdata->chstat.sent_xmit >= devdata->chstat.got_xmit_done) &&
-            (devdata->chstat.sent_xmit - devdata->chstat.got_xmit_done >=
-            devdata->max_outstanding_net_xmits)) ||
-            ((devdata->chstat.sent_xmit < devdata->chstat.got_xmit_done) &&
-            (ULONG_MAX - devdata->chstat.got_xmit_done +
-             devdata->chstat.sent_xmit >=
-             devdata->max_outstanding_net_xmits))) {
+       if (vnic_hit_high_watermark(devdata,
+                                   devdata->max_outstanding_net_xmits)) {
                /* too many NET_XMITs queued over to IOVM - need to wait
                 */
                devdata->chstat.reject_count++;
@@ -957,13 +1000,8 @@ visornic_xmit(struct sk_buff *skb, struct net_device *netdev)
        /* check to see if we have hit the high watermark for
         * netif_stop_queue()
         */
-       if (((devdata->chstat.sent_xmit >= devdata->chstat.got_xmit_done) &&
-            (devdata->chstat.sent_xmit - devdata->chstat.got_xmit_done >=
-             devdata->upper_threshold_net_xmits)) ||
-           ((devdata->chstat.sent_xmit < devdata->chstat.got_xmit_done) &&
-            (ULONG_MAX - devdata->chstat.got_xmit_done +
-             devdata->chstat.sent_xmit >=
-             devdata->upper_threshold_net_xmits))) {
+       if (vnic_hit_high_watermark(devdata,
+                                   devdata->upper_threshold_net_xmits)) {
                /* too many NET_XMITs queued over to IOVM - need to wait */
                netif_stop_queue(netdev); /* calling stop queue - call
                                           * netif_wake_queue() after lower
@@ -1457,13 +1495,13 @@ static ssize_t info_debugfs_read(struct file *file, char __user *buf,
                                     " num_rcv_bufs = %d\n",
                                     devdata->num_rcv_bufs);
                str_pos += scnprintf(vbuf + str_pos, len - str_pos,
-                                    " max_oustanding_next_xmits = %d\n",
+                                    " max_oustanding_next_xmits = %lu\n",
                                    devdata->max_outstanding_net_xmits);
                str_pos += scnprintf(vbuf + str_pos, len - str_pos,
-                                    " upper_threshold_net_xmits = %d\n",
+                                    " upper_threshold_net_xmits = %lu\n",
                                     devdata->upper_threshold_net_xmits);
                str_pos += scnprintf(vbuf + str_pos, len - str_pos,
-                                    " lower_threshold_net_xmits = %d\n",
+                                    " lower_threshold_net_xmits = %lu\n",
                                     devdata->lower_threshold_net_xmits);
                str_pos += scnprintf(vbuf + str_pos, len - str_pos,
                                     " queuefullmsg_logged = %d\n",
@@ -1562,6 +1600,9 @@ static ssize_t info_debugfs_read(struct file *file, char __user *buf,
                                     " netif_queue = %s\n",
                                     netif_queue_stopped(devdata->netdev) ?
                                     "stopped" : "running");
+               str_pos += scnprintf(vbuf + str_pos, len - str_pos,
+                                    " xmits_outstanding = %lu\n",
+                                    devdata_xmits_outstanding(devdata));
        }
        rcu_read_unlock();
        bytes_read = simple_read_from_buffer(buf, len, offset, vbuf, str_pos);
@@ -1655,16 +1696,8 @@ drain_queue(struct uiscmdrsp *cmdrsp, struct visornic_devdata *devdata)
                                 * the lower watermark for
                                 * netif_wake_queue()
                                 */
-                               if (((devdata->chstat.sent_xmit >=
-                                   devdata->chstat.got_xmit_done) &&
-                                   (devdata->chstat.sent_xmit -
-                                   devdata->chstat.got_xmit_done <=
-                                   devdata->lower_threshold_net_xmits)) ||
-                                   ((devdata->chstat.sent_xmit <
-                                   devdata->chstat.got_xmit_done) &&
-                                   (ULONG_MAX - devdata->chstat.got_xmit_done
-                                   + devdata->chstat.sent_xmit <=
-                                   devdata->lower_threshold_net_xmits))) {
+                               if (vnic_hit_low_watermark(devdata,
+                                       devdata->lower_threshold_net_xmits)) {
                                        /* enough NET_XMITs completed
                                         * so can restart netif queue
                                         */
@@ -1834,12 +1867,15 @@ static int visornic_probe(struct visor_device *dev)
 
        /* set the net_xmit outstanding threshold */
        /* always leave two slots open but you should have 3 at a minimum */
+       /* note that max_outstanding_net_xmits must be > 0 */
        devdata->max_outstanding_net_xmits =
-               max(3, ((devdata->num_rcv_bufs / 3) - 2));
+               max_t(unsigned long, 3, ((devdata->num_rcv_bufs / 3) - 2));
        devdata->upper_threshold_net_xmits =
-               max(2, devdata->max_outstanding_net_xmits - 1);
+               max_t(unsigned long,
+                     2, (devdata->max_outstanding_net_xmits - 1));
        devdata->lower_threshold_net_xmits =
-               max(1, devdata->max_outstanding_net_xmits / 2);
+               max_t(unsigned long,
+                     1, (devdata->max_outstanding_net_xmits / 2));
 
        skb_queue_head_init(&devdata->xmitbufhead);