xen-netback: Adding debugfs "io_ring_qX" files

This patch adds debugfs capabilities to netback. There used to be a similar
patch floating around for classic kernel, but it used procfs. It is based on a
very similar blkback patch.
It creates xen-netback/[vifname]/io_ring_q[queueno] files, reading them output
various ring variables etc. Writing "kick" into it imitates an interrupt
happened, it can be useful to check whether the ring is just stalled due to a
missed interrupt.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 200 insertions, 2 deletions

diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
index 2532ce85d718..28c98229e95f 100644
--- a/drivers/net/xen-netback/common.h
+++ b/drivers/net/xen-netback/common.h
@@ -44,6 +44,7 @@
 #include <xen/interface/grant_table.h>
 #include <xen/grant_table.h>
 #include <xen/xenbus.h>
+#include <linux/debugfs.h>
 
 typedef unsigned int pending_ring_idx_t;
 #define INVALID_PENDING_RING_IDX (~0U)
@@ -224,6 +225,10 @@ struct xenvif {
         struct xenvif_queue *queues;
         unsigned int num_queues; /* active queues, resource allocated */
 
+#ifdef CONFIG_DEBUG_FS
+        struct dentry *xenvif_dbg_root;
+#endif
+
         /* Miscellaneous private stuff. */
         struct net_device *dev;
 };
@@ -297,10 +302,16 @@ static inline pending_ring_idx_t nr_pending_reqs(struct xenvif_queue *queue)
 /* Callback from stack when TX packet can be released */
 void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success);
 
+irqreturn_t xenvif_interrupt(int irq, void *dev_id);
+
 extern bool separate_tx_rx_irq;
 
 extern unsigned int rx_drain_timeout_msecs;
 extern unsigned int rx_drain_timeout_jiffies;
 extern unsigned int xenvif_max_queues;
 
+#ifdef CONFIG_DEBUG_FS
+extern struct dentry *xen_netback_dbg_root;
+#endif
+
 #endif /* __XEN_NETBACK__COMMON_H__ */
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 9e97c7ca0ddd..ef75b45e5085 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -102,7 +102,7 @@ static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id)
         return IRQ_HANDLED;
 }
 
-static irqreturn_t xenvif_interrupt(int irq, void *dev_id)
+irqreturn_t xenvif_interrupt(int irq, void *dev_id)
 {
         xenvif_tx_interrupt(irq, dev_id);
         xenvif_rx_interrupt(irq, dev_id);
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 1844a47636b6..77127ca08ca4 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1987,6 +1987,13 @@ static int __init netback_init(void)
 
         rx_drain_timeout_jiffies = msecs_to_jiffies(rx_drain_timeout_msecs);
 
+#ifdef CONFIG_DEBUG_FS
+        xen_netback_dbg_root = debugfs_create_dir("xen-netback", NULL);
+        if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+                pr_warn("Init of debugfs returned %ld!\n",
+                        PTR_ERR(xen_netback_dbg_root));
+#endif /* CONFIG_DEBUG_FS */
+
         return 0;
 
 failed_init:
@@ -1997,6 +2004,10 @@ module_init(netback_init);
 
 static void __exit netback_fini(void)
 {
+#ifdef CONFIG_DEBUG_FS
+        if (!IS_ERR_OR_NULL(xen_netback_dbg_root))
+                debugfs_remove_recursive(xen_netback_dbg_root);
+#endif /* CONFIG_DEBUG_FS */
         xenvif_xenbus_fini();
 }
 module_exit(netback_fini);
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
index 3d85acd84bad..580517d857bf 100644
--- a/drivers/net/xen-netback/xenbus.c
+++ b/drivers/net/xen-netback/xenbus.c
@@ -44,6 +44,175 @@ static void unregister_hotplug_status_watch(struct backend_info *be);
 static void set_backend_state(struct backend_info *be,
                               enum xenbus_state state);
 
+#ifdef CONFIG_DEBUG_FS
+struct dentry *xen_netback_dbg_root = NULL;
+
+static int xenvif_read_io_ring(struct seq_file *m, void *v)
+{
+        struct xenvif_queue *queue = m->private;
+        struct xen_netif_tx_back_ring *tx_ring = &queue->tx;
+        struct xen_netif_rx_back_ring *rx_ring = &queue->rx;
+
+        if (tx_ring->sring) {
+                struct xen_netif_tx_sring *sring = tx_ring->sring;
+
+                seq_printf(m, "Queue %d\nTX: nr_ents %u\n", queue->id,
+                           tx_ring->nr_ents);
+                seq_printf(m, "req prod %u (%d) cons %u (%d) event %u (%d)\n",
+                           sring->req_prod,
+                           sring->req_prod - sring->rsp_prod,
+                           tx_ring->req_cons,
+                           tx_ring->req_cons - sring->rsp_prod,
+                           sring->req_event,
+                           sring->req_event - sring->rsp_prod);
+                seq_printf(m, "rsp prod %u (base) pvt %u (%d) event %u (%d)\n",
+                           sring->rsp_prod,
+                           tx_ring->rsp_prod_pvt,
+                           tx_ring->rsp_prod_pvt - sring->rsp_prod,
+                           sring->rsp_event,
+                           sring->rsp_event - sring->rsp_prod);
+                seq_printf(m, "pending prod %u pending cons %u nr_pending_reqs %u\n",
+                           queue->pending_prod,
+                           queue->pending_cons,
+                           nr_pending_reqs(queue));
+                seq_printf(m, "dealloc prod %u dealloc cons %u dealloc_queue %u\n\n",
+                           queue->dealloc_prod,
+                           queue->dealloc_cons,
+                           queue->dealloc_prod - queue->dealloc_cons);
+        }
+
+        if (rx_ring->sring) {
+                struct xen_netif_rx_sring *sring = rx_ring->sring;
+
+                seq_printf(m, "RX: nr_ents %u\n", rx_ring->nr_ents);
+                seq_printf(m, "req prod %u (%d) cons %u (%d) event %u (%d)\n",
+                           sring->req_prod,
+                           sring->req_prod - sring->rsp_prod,
+                           rx_ring->req_cons,
+                           rx_ring->req_cons - sring->rsp_prod,
+                           sring->req_event,
+                           sring->req_event - sring->rsp_prod);
+                seq_printf(m, "rsp prod %u (base) pvt %u (%d) event %u (%d)\n\n",
+                           sring->rsp_prod,
+                           rx_ring->rsp_prod_pvt,
+                           rx_ring->rsp_prod_pvt - sring->rsp_prod,
+                           sring->rsp_event,
+                           sring->rsp_event - sring->rsp_prod);
+        }
+
+        seq_printf(m, "NAPI state: %lx NAPI weight: %d TX queue len %u\n"
+                   "Credit timer_pending: %d, credit: %lu, usec: %lu\n"
+                   "remaining: %lu, expires: %lu, now: %lu\n",
+                   queue->napi.state, queue->napi.weight,
+                   skb_queue_len(&queue->tx_queue),
+                   timer_pending(&queue->credit_timeout),
+                   queue->credit_bytes,
+                   queue->credit_usec,
+                   queue->remaining_credit,
+                   queue->credit_timeout.expires,
+                   jiffies);
+
+        return 0;
+}
+
+#define XENVIF_KICK_STR "kick"
+
+static ssize_t
+xenvif_write_io_ring(struct file *filp, const char __user *buf, size_t count,
+                     loff_t *ppos)
+{
+        struct xenvif_queue *queue =
+                ((struct seq_file *)filp->private_data)->private;
+        int len;
+        char write[sizeof(XENVIF_KICK_STR)];
+
+        /* don't allow partial writes and check the length */
+        if (*ppos != 0)
+                return 0;
+        if (count < sizeof(XENVIF_KICK_STR) - 1)
+                return -ENOSPC;
+
+        len = simple_write_to_buffer(write,
+                                     sizeof(write),
+                                     ppos,
+                                     buf,
+                                     count);
+        if (len < 0)
+                return len;
+
+        if (!strncmp(write, XENVIF_KICK_STR, sizeof(XENVIF_KICK_STR) - 1))
+                xenvif_interrupt(0, (void *)queue);
+        else {
+                pr_warn("Unknown command to io_ring_q%d. Available: kick\n",
+                        queue->id);
+                count = -EINVAL;
+        }
+        return count;
+}
+
+static int xenvif_dump_open(struct inode *inode, struct file *filp)
+{
+        int ret;
+        void *queue = NULL;
+
+        if (inode->i_private)
+                queue = inode->i_private;
+        ret = single_open(filp, xenvif_read_io_ring, queue);
+        filp->f_mode |= FMODE_PWRITE;
+        return ret;
+}
+
+static const struct file_operations xenvif_dbg_io_ring_ops_fops = {
+        .owner = THIS_MODULE,
+        .open = xenvif_dump_open,
+        .read = seq_read,
+        .llseek = seq_lseek,
+        .release = single_release,
+        .write = xenvif_write_io_ring,
+};
+
+static void xenvif_debugfs_addif(struct xenvif_queue *queue)
+{
+        struct dentry *pfile;
+        struct xenvif *vif = queue->vif;
+        int i;
+
+        if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+                return;
+
+        vif->xenvif_dbg_root = debugfs_create_dir(vif->dev->name,
+                                                  xen_netback_dbg_root);
+        if (!IS_ERR_OR_NULL(vif->xenvif_dbg_root)) {
+                for (i = 0; i < vif->num_queues; ++i) {
+                        char filename[sizeof("io_ring_q") + 4];
+
+                        snprintf(filename, sizeof(filename), "io_ring_q%d", i);
+                        pfile = debugfs_create_file(filename,
+                                                    S_IRUSR | S_IWUSR,
+                                                    vif->xenvif_dbg_root,
+                                                    &vif->queues[i],
+                                                    &xenvif_dbg_io_ring_ops_fops);
+                        if (IS_ERR_OR_NULL(pfile))
+                                pr_warn("Creation of io_ring file returned %ld!\n",
+                                        PTR_ERR(pfile));
+                }
+        } else
+                netdev_warn(vif->dev,
+                            "Creation of vif debugfs dir returned %ld!\n",
+                            PTR_ERR(vif->xenvif_dbg_root));
+}
+
+static void xenvif_debugfs_delif(struct xenvif *vif)
+{
+        if (IS_ERR_OR_NULL(xen_netback_dbg_root))
+                return;
+
+        if (!IS_ERR_OR_NULL(vif->xenvif_dbg_root))
+                debugfs_remove_recursive(vif->xenvif_dbg_root);
+        vif->xenvif_dbg_root = NULL;
+}
+#endif /* CONFIG_DEBUG_FS */
+
 static int netback_remove(struct xenbus_device *dev)
 {
         struct backend_info *be = dev_get_drvdata(&dev->dev);
@@ -246,8 +415,12 @@ static void backend_create_xenvif(struct backend_info *be)
 
 static void backend_disconnect(struct backend_info *be)
 {
-        if (be->vif)
+        if (be->vif) {
+#ifdef CONFIG_DEBUG_FS
+                xenvif_debugfs_delif(be->vif);
+#endif /* CONFIG_DEBUG_FS */
                 xenvif_disconnect(be->vif);
+        }
 }
 
 static void backend_connect(struct backend_info *be)
@@ -560,6 +733,9 @@ static void connect(struct backend_info *be)
                         be->vif->num_queues = queue_index;
                         goto err;
                 }
+#ifdef CONFIG_DEBUG_FS
+                xenvif_debugfs_addif(queue);
+#endif /* CONFIG_DEBUG_FS */
         }
 
         /* Initialisation completed, tell core driver the number of