[S390] hvc_iucv: Limit rate of outgoing IUCV messages

This patch introduces a send buffer to limit outgoing IUCV messages up to
a maximum of 25 IUCV messages per second.

If no communication path to a IUCV HVC terminal exist, any data written to
the terminal is discarded.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 174 insertions, 37 deletions

diff --git a/drivers/char/hvc_iucv.c b/drivers/char/hvc_iucv.c
index a80d92233169..a23f7e8fba86 100644
--- a/drivers/char/hvc_iucv.c
+++ b/drivers/char/hvc_iucv.c
@@ -12,9 +12,11 @@
 
 #include <linux/types.h>
 #include <asm/ebcdic.h>
+#include <linux/delay.h>
 #include <linux/mempool.h>
 #include <linux/module.h>
 #include <linux/tty.h>
+#include <linux/wait.h>
 #include <net/iucv/iucv.h>
 
 #include "hvc_console.h"
@@ -37,7 +39,7 @@
 struct iucv_tty_msg {
         u8      version;                /* Message version */
         u8      type;                   /* Message type */
-#define MSG_MAX_DATALEN         (~(u16)0)
+#define MSG_MAX_DATALEN         ((u16)(~0))
         u16     datalen;                /* Payload length */
         u8      data[];                 /* Payload buffer */
 } __attribute__((packed));
@@ -60,6 +62,12 @@ struct hvc_iucv_private {
         enum tty_state_t        tty_state;      /* TTY status */
         struct iucv_path        *path;          /* IUCV path pointer */
         spinlock_t              lock;           /* hvc_iucv_private lock */
+#define SNDBUF_SIZE             (PAGE_SIZE)     /* must be < MSG_MAX_DATALEN */
+        void                    *sndbuf;        /* send buffer            */
+        size_t                  sndbuf_len;     /* length of send buffer  */
+#define QUEUE_SNDBUF_DELAY      (HZ / 25)
+        struct delayed_work     sndbuf_work;    /* work: send iucv msg(s) */
+        wait_queue_head_t       sndbuf_waitq;   /* wait for send completion */
         struct list_head        tty_outqueue;   /* outgoing IUCV messages */
         struct list_head        tty_inqueue;    /* incoming IUCV messages */
 };
@@ -318,57 +326,118 @@ static int hvc_iucv_get_chars(uint32_t vtermno, char *buf, int count)
 }
 
 /**
- * hvc_iucv_send() - Send an IUCV message containing terminal data.
+ * hvc_iucv_queue() - Buffer terminal data for sending.
  * @priv:       Pointer to struct hvc_iucv_private instance.
  * @buf:        Buffer containing data to send.
- * @size:       Size of buffer and amount of data to send.
+ * @count:      Size of buffer and amount of data to send.
  *
- * If an IUCV communication path is established, the function copies the buffer
- * data to a newly allocated struct iucv_tty_buffer element, sends the data and
- * puts the element to the outqueue.
+ * The function queues data for sending. To actually send the buffered data,
+ * a work queue function is * scheduled (with QUEUE_SNDBUF_DELAY).
+ * The function returns the number of data bytes that has been buffered.
  *
- * If there is no IUCV communication path established, the function returns 0.
+ * If the device is not connected, data is ignored and the function returns
+ * @count.
+ * If the buffer is full, the function returns 0.
  * If an existing IUCV communicaton path has been severed, the function returns
  * -EPIPE (can be passed to HVC layer to cause a tty hangup).
  */
-static int hvc_iucv_send(struct hvc_iucv_private *priv, const char *buf,
+static int hvc_iucv_queue(struct hvc_iucv_private *priv, const char *buf,
                          int count)
 {
+        size_t len;
+
+        if (priv->iucv_state == IUCV_DISCONN)
+                return count;                   /* ignore data */
+
+        if (priv->iucv_state == IUCV_SEVERED)
+                return -EPIPE;
+
+        len = min_t(size_t, count, SNDBUF_SIZE - priv->sndbuf_len);
+        if (!len)
+                return 0;
+
+        memcpy(priv->sndbuf + priv->sndbuf_len, buf, len);
+        priv->sndbuf_len += len;
+
+        if (priv->iucv_state == IUCV_CONNECTED)
+                schedule_delayed_work(&priv->sndbuf_work, QUEUE_SNDBUF_DELAY);
+
+        return len;
+}
+
+/**
+ * hvc_iucv_send() - Send an IUCV message containing terminal data.
+ * @priv:       Pointer to struct hvc_iucv_private instance.
+ *
+ * If an IUCV communication path has been established, the queued data
+ * for output are sent via an IUCV message.
+ *
+ * If there is no IUCV communication path established, the function returns 0.
+ * If an existing IUCV communicaton path has been severed, the function returns
+ * -EPIPE.
+ */
+static int hvc_iucv_send(struct hvc_iucv_private *priv)
+{
         struct iucv_tty_buffer *sb;
-        int rc;
-        u16 len;
+        int rc, len;
 
         if (priv->iucv_state == IUCV_SEVERED)
                 return -EPIPE;
 
         if (priv->iucv_state == IUCV_DISCONN)
-                return 0;
+                return -EIO;
 
-        len = min_t(u16, MSG_MAX_DATALEN, count);
+        if (!priv->sndbuf_len)
+                return 0;
 
         /* allocate internal buffer to store msg data and also compute total
          * message length */
-        sb = alloc_tty_buffer(len, GFP_ATOMIC);
+        sb = alloc_tty_buffer(priv->sndbuf_len, GFP_ATOMIC);
         if (!sb)
                 return -ENOMEM;
 
-        sb->mbuf->datalen = len;
-        memcpy(sb->mbuf->data, buf, len);
+        memcpy(sb->mbuf->data, priv->sndbuf, priv->sndbuf_len);
+        sb->mbuf->datalen = (u16) priv->sndbuf_len;
+        sb->msg.length = MSG_SIZE(sb->mbuf->datalen);
 
         list_add_tail(&sb->list, &priv->tty_outqueue);
 
         rc = __iucv_message_send(priv->path, &sb->msg, 0, 0,
                                  (void *) sb->mbuf, sb->msg.length);
         if (rc) {
+                /* drop the message here; however we might want to handle
+                 * 0x03 (msg limit reached) by trying again... */
                 list_del(&sb->list);
                 destroy_tty_buffer(sb);
-                len = 0;
         }
+        len = priv->sndbuf_len;
+        priv->sndbuf_len = 0;
 
         return len;
 }
 
 /**
+ * hvc_iucv_sndbuf_work() - Send buffered data over IUCV
+ * @work:       Work structure.
+ *
+ * The function sends buffered output data over IUCV and, if necessary,
+ * reschedules itself if not all buffered data could be sent.
+ */
+static void hvc_iucv_sndbuf_work(struct work_struct *work)
+{
+        struct hvc_iucv_private *priv;
+
+        priv = container_of(work, struct hvc_iucv_private, sndbuf_work.work);
+
+        if (!priv)
+                return;
+
+        spin_lock_bh(&priv->lock);
+        hvc_iucv_send(priv);
+        spin_unlock_bh(&priv->lock);
+}
+
+/**
  * hvc_iucv_put_chars() - HVC put_chars operation.
  * @vtermno:    HVC virtual terminal number.
  * @buf:        Pointer to an buffer to read data from
@@ -385,7 +454,7 @@ static int hvc_iucv_send(struct hvc_iucv_private *priv, const char *buf,
 static int hvc_iucv_put_chars(uint32_t vtermno, const char *buf, int count)
 {
         struct hvc_iucv_private *priv = hvc_iucv_get_private(vtermno);
-        int sent;
+        int queued;
 
         if (count <= 0)
                 return 0;
@@ -394,10 +463,10 @@ static int hvc_iucv_put_chars(uint32_t vtermno, const char *buf, int count)
                 return -ENODEV;
 
         spin_lock(&priv->lock);
-        sent = hvc_iucv_send(priv, buf, count);
+        queued = hvc_iucv_queue(priv, buf, count);
         spin_unlock(&priv->lock);
 
-        return sent;
+        return queued;
 }
 
 /**
@@ -441,6 +510,46 @@ static void hvc_iucv_cleanup(struct hvc_iucv_private *priv)
 
         priv->tty_state = TTY_CLOSED;
         priv->iucv_state = IUCV_DISCONN;
+
+        priv->sndbuf_len = 0;
+}
+
+/**
+ * tty_outqueue_empty() - Test if the tty outq is empty
+ * @priv:       Pointer to struct hvc_iucv_private instance.
+ */
+static inline int tty_outqueue_empty(struct hvc_iucv_private *priv)
+{
+        int rc;
+
+        spin_lock_bh(&priv->lock);
+        rc = list_empty(&priv->tty_outqueue);
+        spin_unlock_bh(&priv->lock);
+
+        return rc;
+}
+
+/**
+ * flush_sndbuf_sync() - Flush send buffer and wait for completion
+ * @priv:       Pointer to struct hvc_iucv_private instance.
+ *
+ * The routine cancels a pending sndbuf work, calls hvc_iucv_send()
+ * to flush any buffered terminal output data and waits for completion.
+ */
+static void flush_sndbuf_sync(struct hvc_iucv_private *priv)
+{
+        int sync_wait;
+
+        cancel_delayed_work_sync(&priv->sndbuf_work);
+
+        spin_lock_bh(&priv->lock);
+        hvc_iucv_send(priv);            /* force sending buffered data */
+        sync_wait = !list_empty(&priv->tty_outqueue); /* anything queued ? */
+        spin_unlock_bh(&priv->lock);
+
+        if (sync_wait)
+                wait_event_timeout(priv->sndbuf_waitq,
+                                   tty_outqueue_empty(priv), HZ);
 }
 
 /**
@@ -471,6 +580,8 @@ static void hvc_iucv_notifier_hangup(struct hvc_struct *hp, int id)
         if (!priv)
                 return;
 
+        flush_sndbuf_sync(priv);
+
         spin_lock_bh(&priv->lock);
         /* NOTE: If the hangup was scheduled by ourself (from the iucv
          *       path_servered callback [IUCV_SEVERED]), then we have to
@@ -510,6 +621,8 @@ static void hvc_iucv_notifier_del(struct hvc_struct *hp, int id)
         if (!priv)
                 return;
 
+        flush_sndbuf_sync(priv);
+
         spin_lock_bh(&priv->lock);
         path = priv->path;              /* save reference to IUCV path */
         priv->path = NULL;
@@ -588,6 +701,9 @@ static	int hvc_iucv_path_pending(struct iucv_path *path,
         priv->path = path;
         priv->iucv_state = IUCV_CONNECTED;
 
+        /* flush buffered output data... */
+        schedule_delayed_work(&priv->sndbuf_work, 5);
+
 out_path_handled:
         spin_unlock(&priv->lock);
         return 0;
@@ -615,15 +731,18 @@ static void hvc_iucv_path_severed(struct iucv_path *path, u8 ipuser[16])
         spin_lock(&priv->lock);
         priv->iucv_state = IUCV_SEVERED;
 
-        /* NOTE: If the tty has not yet been opened by a getty program
-         *       (e.g. to see console messages), then cleanup the
-         *       hvc_iucv_private structure to allow re-connects.
+        /* If the tty has not yet been opened, clean up the hvc_iucv_private
+         * structure to allow re-connects.
          *
-         *       If the tty has been opened, the get_chars() callback returns
-         *       -EPIPE to signal the hvc console layer to hang up the tty. */
+         * If it has been opened, let get_chars() return -EPIPE to signal the
+         * HVC layer to hang up the tty.
+         * If so, we need to wake up the HVC thread to call get_chars()...
+         */
         priv->path = NULL;
         if (priv->tty_state == TTY_CLOSED)
                 hvc_iucv_cleanup(priv);
+        else
+                hvc_kick();
         spin_unlock(&priv->lock);
 
         /* finally sever path (outside of priv->lock due to lock ordering) */
@@ -648,6 +767,12 @@ static void hvc_iucv_msg_pending(struct iucv_path *path,
         struct hvc_iucv_private *priv = path->private;
         struct iucv_tty_buffer *rb;
 
+        /* reject messages that exceed max size of iucv_tty_msg->datalen */
+        if (msg->length > MSG_SIZE(MSG_MAX_DATALEN)) {
+                iucv_message_reject(path, msg);
+                return;
+        }
+
         spin_lock(&priv->lock);
 
         /* reject messages if tty has not yet been opened */
@@ -656,7 +781,7 @@ static void hvc_iucv_msg_pending(struct iucv_path *path,
                 goto unlock_return;
         }
 
-        /* allocate buffer an empty buffer element */
+        /* allocate tty buffer to save iucv msg only */
         rb = alloc_tty_buffer(0, GFP_ATOMIC);
         if (!rb) {
                 iucv_message_reject(path, msg);
@@ -666,7 +791,7 @@ static void hvc_iucv_msg_pending(struct iucv_path *path,
 
         list_add_tail(&rb->list, &priv->tty_inqueue);
 
-        hvc_kick();     /* wakup hvc console thread */
+        hvc_kick();     /* wake up hvc console thread */
 
 unlock_return:
         spin_unlock(&priv->lock);
@@ -697,6 +822,7 @@ static void hvc_iucv_msg_complete(struct iucv_path *path,
                         list_move(&ent->list, &list_remove);
                         break;
                 }
+        wake_up(&priv->sndbuf_waitq);
         spin_unlock(&priv->lock);
         destroy_tty_buffer_list(&list_remove);
 }
@@ -732,16 +858,28 @@ static int __init hvc_iucv_alloc(int id)
         spin_lock_init(&priv->lock);
         INIT_LIST_HEAD(&priv->tty_outqueue);
         INIT_LIST_HEAD(&priv->tty_inqueue);
+        INIT_DELAYED_WORK(&priv->sndbuf_work, hvc_iucv_sndbuf_work);
+        init_waitqueue_head(&priv->sndbuf_waitq);
+
+        priv->sndbuf = (void *) get_zeroed_page(GFP_KERNEL);
+        if (!priv->sndbuf) {
+                kfree(priv);
+                return -ENOMEM;
+        }
 
         /* Finally allocate hvc */
-        priv->hvc = hvc_alloc(HVC_IUCV_MAGIC + id,
-                              HVC_IUCV_MAGIC + id, &hvc_iucv_ops, PAGE_SIZE);
+        priv->hvc = hvc_alloc(HVC_IUCV_MAGIC + id, /*             PAGE_SIZE */
+                              HVC_IUCV_MAGIC + id, &hvc_iucv_ops, 256);
         if (IS_ERR(priv->hvc)) {
                 rc = PTR_ERR(priv->hvc);
+                free_page((unsigned long) priv->sndbuf);
                 kfree(priv);
                 return rc;
         }
 
+        /* kick khvcd thread; instead of using polling */
+        priv->hvc->irq_requested = 1;
+
         /* setup iucv related information */
         snprintf(name, 9, "lnxhvc%-2d", id);
         memcpy(priv->srv_name, name, 8);
@@ -759,8 +897,8 @@ static int __init hvc_iucv_init(void)
         int rc, i;
 
         if (!MACHINE_IS_VM) {
-                pr_warning("The z/VM IUCV Hypervisor console cannot be "
-                           "used without z/VM.\n");
+                pr_info("The z/VM IUCV HVC device driver cannot "
+                           "be used without z/VM\n");
                 return -ENODEV;
         }
 
@@ -774,16 +912,14 @@ static int __init hvc_iucv_init(void)
                                            sizeof(struct iucv_tty_buffer),
                                            0, 0, NULL);
         if (!hvc_iucv_buffer_cache) {
-                pr_err("Not enough memory for driver initialization "
-                        "(rs=%d).\n", 1);
+                pr_err("Allocating memory failed with reason code=%d\n", 1);
                 return -ENOMEM;
         }
 
         hvc_iucv_mempool = mempool_create_slab_pool(MEMPOOL_MIN_NR,
                                                     hvc_iucv_buffer_cache);
         if (!hvc_iucv_mempool) {
-                pr_err("Not enough memory for driver initialization "
-                        "(rs=%d).\n", 2);
+                pr_err("Allocating memory failed with reason code=%d\n", 2);
                 kmem_cache_destroy(hvc_iucv_buffer_cache);
                 return -ENOMEM;
         }
@@ -792,8 +928,8 @@ static int __init hvc_iucv_init(void)
         for (i = 0; i < hvc_iucv_devices; i++) {
                 rc = hvc_iucv_alloc(i);
                 if (rc) {
-                        pr_err("Could not create new z/VM IUCV HVC backend "
-                                "rc=%d.\n", rc);
+                        pr_err("Creating a new HVC terminal device "
+                                "failed with error code=%d\n", rc);
                         goto out_error_hvc;
                 }
         }
@@ -801,7 +937,8 @@ static int __init hvc_iucv_init(void)
         /* register IUCV callback handler */
         rc = iucv_register(&hvc_iucv_handler, 0);
         if (rc) {
-                pr_err("Could not register iucv handler (rc=%d).\n", rc);
+                pr_err("Registering IUCV handlers failed with error code=%d\n",
+                        rc);
                 goto out_error_iucv;
         }