4 files changed, 138 insertions, 7 deletions

diff --git a/drivers/s390/char/sclp.c b/drivers/s390/char/sclp.c
index bd6871bf545a..a77febeead1f 100644
--- a/drivers/s390/char/sclp.c
+++ b/drivers/s390/char/sclp.c
@@ -50,11 +50,42 @@ static char sclp_init_sccb[PAGE_SIZE] __attribute__((__aligned__(PAGE_SIZE)));
 /* Suspend request */
 static DECLARE_COMPLETION(sclp_request_queue_flushed);
 
+/* Number of console pages to allocate, used by sclp_con.c and sclp_vt220.c */
+int sclp_console_pages = SCLP_CONSOLE_PAGES;
+/* Flag to indicate if buffer pages are dropped on buffer full condition */
+int sclp_console_drop = 0;
+/* Number of times the console dropped buffer pages */
+unsigned long sclp_console_full;
+
 static void sclp_suspend_req_cb(struct sclp_req *req, void *data)
 {
         complete(&sclp_request_queue_flushed);
 }
 
+static int __init sclp_setup_console_pages(char *str)
+{
+        int pages, rc;
+
+        rc = kstrtoint(str, 0, &pages);
+        if (!rc && pages >= SCLP_CONSOLE_PAGES)
+                sclp_console_pages = pages;
+        return 1;
+}
+
+__setup("sclp_con_pages=", sclp_setup_console_pages);
+
+static int __init sclp_setup_console_drop(char *str)
+{
+        int drop, rc;
+
+        rc = kstrtoint(str, 0, &drop);
+        if (!rc && drop)
+                sclp_console_drop = 1;
+        return 1;
+}
+
+__setup("sclp_con_drop=", sclp_setup_console_drop);
+
 static struct sclp_req sclp_suspend_req;
 
 /* Timer for request retries. */
@@ -1013,11 +1044,47 @@ static const struct dev_pm_ops sclp_pm_ops = {
         .restore        = sclp_restore,
 };
 
+static ssize_t sclp_show_console_pages(struct device_driver *dev, char *buf)
+{
+        return sprintf(buf, "%i\n", sclp_console_pages);
+}
+
+static DRIVER_ATTR(con_pages, S_IRUSR, sclp_show_console_pages, NULL);
+
+static ssize_t sclp_show_con_drop(struct device_driver *dev, char *buf)
+{
+        return sprintf(buf, "%i\n", sclp_console_drop);
+}
+
+static DRIVER_ATTR(con_drop, S_IRUSR, sclp_show_con_drop, NULL);
+
+static ssize_t sclp_show_console_full(struct device_driver *dev, char *buf)
+{
+        return sprintf(buf, "%lu\n", sclp_console_full);
+}
+
+static DRIVER_ATTR(con_full, S_IRUSR, sclp_show_console_full, NULL);
+
+static struct attribute *sclp_drv_attrs[] = {
+        &driver_attr_con_pages.attr,
+        &driver_attr_con_drop.attr,
+        &driver_attr_con_full.attr,
+        NULL,
+};
+static struct attribute_group sclp_drv_attr_group = {
+        .attrs = sclp_drv_attrs,
+};
+static const struct attribute_group *sclp_drv_attr_groups[] = {
+        &sclp_drv_attr_group,
+        NULL,
+};
+
 static struct platform_driver sclp_pdrv = {
         .driver = {
                 .name   = "sclp",
                 .owner  = THIS_MODULE,
                 .pm     = &sclp_pm_ops,
+                .groups = sclp_drv_attr_groups,
         },
 };
 
@@ -1096,10 +1163,12 @@ static __init int sclp_initcall(void)
         rc = platform_driver_register(&sclp_pdrv);
         if (rc)
                 return rc;
+
         sclp_pdev = platform_device_register_simple("sclp", -1, NULL, 0);
         rc = IS_ERR(sclp_pdev) ? PTR_ERR(sclp_pdev) : 0;
         if (rc)
                 goto fail_platform_driver_unregister;
+
         rc = atomic_notifier_chain_register(&panic_notifier_list,
                                             &sclp_on_panic_nb);
         if (rc)
diff --git a/drivers/s390/char/sclp.h b/drivers/s390/char/sclp.h
index 25bcd4c0ed82..e11383f5d3d2 100644
--- a/drivers/s390/char/sclp.h
+++ b/drivers/s390/char/sclp.h
@@ -15,7 +15,7 @@
 
 /* maximum number of pages concerning our own memory management */
 #define MAX_KMEM_PAGES (sizeof(unsigned long) << 3)
-#define MAX_CONSOLE_PAGES       6
+#define SCLP_CONSOLE_PAGES      6
 
 #define EVTYP_OPCMD             0x01
 #define EVTYP_MSG               0x02
@@ -175,6 +175,10 @@ int sclp_service_call(sclp_cmdw_t command, void *sccb);
 int sclp_sdias_init(void);
 void sclp_sdias_exit(void);
 
+extern int sclp_console_pages;
+extern int sclp_console_drop;
+extern unsigned long sclp_console_full;
+
 /* useful inlines */
 
 /* VM uses EBCDIC 037, LPAR+native(SE+HMC) use EBCDIC 500 */
diff --git a/drivers/s390/char/sclp_con.c b/drivers/s390/char/sclp_con.c
index ecf45c54f8c4..5880def98fc1 100644
--- a/drivers/s390/char/sclp_con.c
+++ b/drivers/s390/char/sclp_con.c
@@ -130,6 +130,31 @@ sclp_console_timeout(unsigned long data)
 }
 
 /*
+ * Drop oldest console buffer if sclp_con_drop is set
+ */
+static int
+sclp_console_drop_buffer(void)
+{
+        struct list_head *list;
+        struct sclp_buffer *buffer;
+        void *page;
+
+        if (!sclp_console_drop)
+                return 0;
+        list = sclp_con_outqueue.next;
+        if (sclp_con_queue_running)
+                /* The first element is in I/O */
+                list = list->next;
+        if (list == &sclp_con_outqueue)
+                return 0;
+        list_del(list);
+        buffer = list_entry(list, struct sclp_buffer, list);
+        page = sclp_unmake_buffer(buffer);
+        list_add_tail((struct list_head *) page, &sclp_con_pages);
+        return 1;
+}
+
+/*
  * Writes the given message to S390 system console
  */
 static void
@@ -150,9 +175,13 @@ sclp_console_write(struct console *console, const char *message,
         do {
                 /* make sure we have a console output buffer */
                 if (sclp_conbuf == NULL) {
+                        if (list_empty(&sclp_con_pages))
+                                sclp_console_full++;
                         while (list_empty(&sclp_con_pages)) {
                                 if (sclp_con_suspended)
                                         goto out;
+                                if (sclp_console_drop_buffer())
+                                        break;
                                 spin_unlock_irqrestore(&sclp_con_lock, flags);
                                 sclp_sync_wait();
                                 spin_lock_irqsave(&sclp_con_lock, flags);
@@ -297,7 +326,7 @@ sclp_console_init(void)
                 return rc;
         /* Allocate pages for output buffering */
         INIT_LIST_HEAD(&sclp_con_pages);
-        for (i = 0; i < MAX_CONSOLE_PAGES; i++) {
+        for (i = 0; i < sclp_console_pages; i++) {
                 page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
                 list_add_tail(page, &sclp_con_pages);
         }
diff --git a/drivers/s390/char/sclp_vt220.c b/drivers/s390/char/sclp_vt220.c
index 5aaaa2ec8df4..4eed38cd0af6 100644
--- a/drivers/s390/char/sclp_vt220.c
+++ b/drivers/s390/char/sclp_vt220.c
@@ -362,6 +362,31 @@ sclp_vt220_timeout(unsigned long data)
 
 #define BUFFER_MAX_DELAY        HZ/20
 
+/*
+ * Drop oldest console buffer if sclp_con_drop is set
+ */
+static int
+sclp_vt220_drop_buffer(void)
+{
+        struct list_head *list;
+        struct sclp_vt220_request *request;
+        void *page;
+
+        if (!sclp_console_drop)
+                return 0;
+        list = sclp_vt220_outqueue.next;
+        if (sclp_vt220_queue_running)
+                /* The first element is in I/O */
+                list = list->next;
+        if (list == &sclp_vt220_outqueue)
+                return 0;
+        list_del(list);
+        request = list_entry(list, struct sclp_vt220_request, list);
+        page = request->sclp_req.sccb;
+        list_add_tail((struct list_head *) page, &sclp_vt220_empty);
+        return 1;
+}
+
 /* 
  * Internal implementation of the write function. Write COUNT bytes of data
  * from memory at BUF
@@ -390,12 +415,16 @@ __sclp_vt220_write(const unsigned char *buf, int count, int do_schedule,
         do {
                 /* Create an sclp output buffer if none exists yet */
                 if (sclp_vt220_current_request == NULL) {
+                        if (list_empty(&sclp_vt220_empty))
+                                sclp_console_full++;
                         while (list_empty(&sclp_vt220_empty)) {
-                                spin_unlock_irqrestore(&sclp_vt220_lock, flags);
                                 if (may_fail || sclp_vt220_suspended)
                                         goto out;
-                                else
-                                        sclp_sync_wait();
+                                if (sclp_vt220_drop_buffer())
+                                        break;
+                                spin_unlock_irqrestore(&sclp_vt220_lock, flags);
+
+                                sclp_sync_wait();
                                 spin_lock_irqsave(&sclp_vt220_lock, flags);
                         }
                         page = (void *) sclp_vt220_empty.next;
@@ -428,8 +457,8 @@ __sclp_vt220_write(const unsigned char *buf, int count, int do_schedule,
                 sclp_vt220_timer.expires = jiffies + BUFFER_MAX_DELAY;
                 add_timer(&sclp_vt220_timer);
         }
-        spin_unlock_irqrestore(&sclp_vt220_lock, flags);
 out:
+        spin_unlock_irqrestore(&sclp_vt220_lock, flags);
         return overall_written;
 }
 
@@ -803,7 +832,7 @@ sclp_vt220_con_init(void)
 
         if (!CONSOLE_IS_SCLP)
                 return 0;
-        rc = __sclp_vt220_init(MAX_CONSOLE_PAGES);
+        rc = __sclp_vt220_init(sclp_console_pages);
         if (rc)
                 return rc;
         /* Attach linux console */