1 files changed, 78 insertions, 48 deletions

diff --git a/drivers/usb/mon/mon_text.c b/drivers/usb/mon/mon_text.c
index f5e1bb5e5217..984f7e12a6a5 100644
--- a/drivers/usb/mon/mon_text.c
+++ b/drivers/usb/mon/mon_text.c
@@ -85,6 +85,8 @@ struct mon_reader_text {
 
         wait_queue_head_t wait;
         int printf_size;
+        size_t printf_offset;
+        size_t printf_togo;
         char *printf_buf;
         struct mutex printf_lock;
 
@@ -376,75 +378,103 @@ err_alloc:
         return rc;
 }
 
-/*
- * For simplicity, we read one record in one system call and throw out
- * what does not fit. This means that the following does not work:
- *   dd if=/dbg/usbmon/0t bs=10
- * Also, we do not allow seeks and do not bother advancing the offset.
- */
+static ssize_t mon_text_copy_to_user(struct mon_reader_text *rp,
+    char __user * const buf, const size_t nbytes)
+{
+        const size_t togo = min(nbytes, rp->printf_togo);
+
+        if (copy_to_user(buf, &rp->printf_buf[rp->printf_offset], togo))
+                return -EFAULT;
+        rp->printf_togo -= togo;
+        rp->printf_offset += togo;
+        return togo;
+}
+
+/* ppos is not advanced since the llseek operation is not permitted. */
 static ssize_t mon_text_read_t(struct file *file, char __user *buf,
-                                size_t nbytes, loff_t *ppos)
+    size_t nbytes, loff_t *ppos)
 {
         struct mon_reader_text *rp = file->private_data;
         struct mon_event_text *ep;
         struct mon_text_ptr ptr;
+        ssize_t ret;
 
-        ep = mon_text_read_wait(rp, file);
-        if (IS_ERR(ep))
-                return PTR_ERR(ep);
         mutex_lock(&rp->printf_lock);
-        ptr.cnt = 0;
-        ptr.pbuf = rp->printf_buf;
-        ptr.limit = rp->printf_size;
-
-        mon_text_read_head_t(rp, &ptr, ep);
-        mon_text_read_statset(rp, &ptr, ep);
-        ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
-            " %d", ep->length);
-        mon_text_read_data(rp, &ptr, ep);
-
-        if (copy_to_user(buf, rp->printf_buf, ptr.cnt))
-                ptr.cnt = -EFAULT;
+
+        if (rp->printf_togo == 0) {
+
+                ep = mon_text_read_wait(rp, file);
+                if (IS_ERR(ep)) {
+                        mutex_unlock(&rp->printf_lock);
+                        return PTR_ERR(ep);
+                }
+                ptr.cnt = 0;
+                ptr.pbuf = rp->printf_buf;
+                ptr.limit = rp->printf_size;
+
+                mon_text_read_head_t(rp, &ptr, ep);
+                mon_text_read_statset(rp, &ptr, ep);
+                ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
+                    " %d", ep->length);
+                mon_text_read_data(rp, &ptr, ep);
+
+                rp->printf_togo = ptr.cnt;
+                rp->printf_offset = 0;
+
+                kmem_cache_free(rp->e_slab, ep);
+        }
+
+        ret = mon_text_copy_to_user(rp, buf, nbytes);
         mutex_unlock(&rp->printf_lock);
-        kmem_cache_free(rp->e_slab, ep);
-        return ptr.cnt;
+        return ret;
 }
 
+/* ppos is not advanced since the llseek operation is not permitted. */
 static ssize_t mon_text_read_u(struct file *file, char __user *buf,
-                                size_t nbytes, loff_t *ppos)
+    size_t nbytes, loff_t *ppos)
 {
         struct mon_reader_text *rp = file->private_data;
         struct mon_event_text *ep;
         struct mon_text_ptr ptr;
+        ssize_t ret;
 
-        ep = mon_text_read_wait(rp, file);
-        if (IS_ERR(ep))
-                return PTR_ERR(ep);
         mutex_lock(&rp->printf_lock);
-        ptr.cnt = 0;
-        ptr.pbuf = rp->printf_buf;
-        ptr.limit = rp->printf_size;
 
-        mon_text_read_head_u(rp, &ptr, ep);
-        if (ep->type == 'E') {
-                mon_text_read_statset(rp, &ptr, ep);
-        } else if (ep->xfertype == USB_ENDPOINT_XFER_ISOC) {
-                mon_text_read_isostat(rp, &ptr, ep);
-                mon_text_read_isodesc(rp, &ptr, ep);
-        } else if (ep->xfertype == USB_ENDPOINT_XFER_INT) {
-                mon_text_read_intstat(rp, &ptr, ep);
-        } else {
-                mon_text_read_statset(rp, &ptr, ep);
+        if (rp->printf_togo == 0) {
+
+                ep = mon_text_read_wait(rp, file);
+                if (IS_ERR(ep)) {
+                        mutex_unlock(&rp->printf_lock);
+                        return PTR_ERR(ep);
+                }
+                ptr.cnt = 0;
+                ptr.pbuf = rp->printf_buf;
+                ptr.limit = rp->printf_size;
+
+                mon_text_read_head_u(rp, &ptr, ep);
+                if (ep->type == 'E') {
+                        mon_text_read_statset(rp, &ptr, ep);
+                } else if (ep->xfertype == USB_ENDPOINT_XFER_ISOC) {
+                        mon_text_read_isostat(rp, &ptr, ep);
+                        mon_text_read_isodesc(rp, &ptr, ep);
+                } else if (ep->xfertype == USB_ENDPOINT_XFER_INT) {
+                        mon_text_read_intstat(rp, &ptr, ep);
+                } else {
+                        mon_text_read_statset(rp, &ptr, ep);
+                }
+                ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
+                    " %d", ep->length);
+                mon_text_read_data(rp, &ptr, ep);
+
+                rp->printf_togo = ptr.cnt;
+                rp->printf_offset = 0;
+
+                kmem_cache_free(rp->e_slab, ep);
         }
-        ptr.cnt += snprintf(ptr.pbuf + ptr.cnt, ptr.limit - ptr.cnt,
-            " %d", ep->length);
-        mon_text_read_data(rp, &ptr, ep);
 
-        if (copy_to_user(buf, rp->printf_buf, ptr.cnt))
-                ptr.cnt = -EFAULT;
+        ret = mon_text_copy_to_user(rp, buf, nbytes);
         mutex_unlock(&rp->printf_lock);
-        kmem_cache_free(rp->e_slab, ep);
-        return ptr.cnt;
+        return ret;
 }
 
 static struct mon_event_text *mon_text_read_wait(struct mon_reader_text *rp,