Re: [Xen-devel] [PATCH net-next v2] xen-netback: Adding debugfs "io_ring_qX" files

From: Konrad Rzeszutek Wilk
Date: Wed Jul 02 2014 - 16:03:08 EST

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In reply to: Zoltan Kiss: "[PATCH net-next v2] xen-netback: Adding debugfs "io_ring_qX" files"
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On Wed, Jul 02, 2014 at 08:53:50PM +0100, Zoltan Kiss wrote:
> 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@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> ---
> v2:
> - use sequential files
> - put everything behind the right config option
> - fix error handling
>
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> index 2532ce8..a2ba1f2 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 /* CONFIG_DEBUG_FS */
> +
> /* 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 /* CONFIG_DEBUG_FS */
> +
> #endif /* __XEN_NETBACK__COMMON_H__ */
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
> index 9e97c7c..ef75b45 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 1844a47..77127ca 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 3d85acd..657884d 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -44,6 +44,164 @@ 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;
> +}
> +
> +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("kick")];

<blinks>
> +
> + /* don't allow partial writes and check the length */
> + if (*ppos != 0)
> + return 0;
> + if (count < sizeof("kick") - 1)

Um, could you just use a #define please?

> + return -ENOSPC;
> +
> + len = simple_write_to_buffer(write,
> + sizeof(write),
> + ppos,
> + buf,
> + count);
> + if (len < 0)
> + return len;
> +
> + if (!strncmp(write, "kick", sizeof("kick") - 1))
> + xenvif_interrupt(0, (void *)queue);
> + else
> + pr_warn("Unknown command to io_ring. Available: kick\n");

It is 'io_ring_q%d'? Why don't you split that back out to the user
instead of the console?

> + 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;
> +
> + 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,
> + 0600,

Pls use macros for that.
> + 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)
> +{

Could you add:

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 +404,13 @@ 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
> + if (!IS_ERR_OR_NULL(xen_netback_dbg_root))
> + xenvif_debugfs_delif(be->vif);

.. and then you can remove these 'if' here
> +#endif /* CONFIG_DEBUG_FS */
> xenvif_disconnect(be->vif);
> + }
> }
>
> static void backend_connect(struct backend_info *be)
> @@ -560,6 +723,10 @@ static void connect(struct backend_info *be)
> be->vif->num_queues = queue_index;
> goto err;
> }
> +#ifdef CONFIG_DEBUG_FS
> + if (!IS_ERR_OR_NULL(xen_netback_dbg_root))

.. and here.
> + xenvif_debugfs_addif(queue);
> +#endif /* CONFIG_DEBUG_FS */
> }
>
> /* Initialisation completed, tell core driver the number of
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
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Next message: Fabian Frederick: "[PATCH 1/1] FS/CODA: use linux/uaccess.h"
Previous message: Fabian Frederick: "[PATCH 1/1] FS/BFS: use bfs prefix for dump_imap"
In reply to: Zoltan Kiss: "[PATCH net-next v2] xen-netback: Adding debugfs "io_ring_qX" files"
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