[PATCH net-next v6 13/15] ibmveth: Expose per-queue buffer pool details via debugfs

[Mingming Cao <mmc@linux.ibm.com>]

With multi-queue RX each queue owns its own set of five buffer pools,
so a 16-queue adapter has 80 of them. Nothing reports their runtime
state: sysfs exposes queue 0 only, and only as configuration, and no
ethtool key is per-pool. When RX drops under load, rx%d_no_buffer_drops
names the queue but not which of its pools ran dry, nor how close the
others are.

Add a read-only buffer_pools debugfs file, one row per RX queue and
buffer pool:

  /sys/kernel/debug/ibmveth/<dev_name>/buffer_pools
  (e.g. /sys/kernel/debug/ibmveth/30000002/buffer_pools)

  Queue  Pool  Count  BuffSize  Active  Available

Active is live allocation (skbuff && free_map), not the sysfs
poolN/active configuration flag.

The root is driver-owned so each adapter directory can use its stable
vio name rather than the mutable netdev->name. It is created in
module_init() and unwound if vio_register_driver() fails.

A multi-line table does not belong in sysfs, so the historical queue-0
ABI is left alone:

  .../poolN/{active,num,size}

Those stay one-value configuration for queue-0 pool classes. Open
copies that geometry to queues 1..N. This series does not add
per-queue pool sysfs dirs.

Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com>
Tested-by: Shaik Abdulla <shaik.abdulla1@ibm.com>
---

Changes in v6:
- create the debugfs root in module_init() instead of lazily on
  first probe, which raced concurrent probes and could orphan the
  directory on ERR_PTR(-EEXIST)
- rename the pool buffer-count column from Size to Count, so the
  debugfs table stops reusing the word sysfs poolN/size spells as a
  byte length on the same pool object
- widen the down banner: geometry above queue 0 is only populated
  once open copies the queue-0 template
- scope the dump RTNL comment to geometry/pool->active; available is
  atomic_read

Changes in v5:
- debugfs buffer_pools_show walks get_num_rx_queues()
- Series renumber: mailed v4 11/14 debugfs -> tip P13 (14->15)
- Path uses stable vio dev_name under a driver-owned root (not netdev
  name - avoids rename/collide)
- rtnl_lock around dump (writers are under RTNL)
- Show Active/Available as 0 when pool !live (debugfs view; free-path
  available clear already in the buffer-submit patch)

Changes in v4:
- Move the all-queue buffer_pools diagnostic from sysfs to debugfs;
  subject updated to match.
- Keep historical queue-0 poolN/{active,num,size} sysfs as one-value
  config (template for MQ); do not add per-queue pool sysfs dirs.

 drivers/net/ethernet/ibm/ibmveth.c | 80 +++++++++++++++++++++++++++++-
 drivers/net/ethernet/ibm/ibmveth.h |  2 +
 2 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index 4f2d956b4c89..954846c9ec7b 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -31,6 +31,7 @@
 #include <linux/ipv6.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/debugfs.h>
 #include <asm/hvcall.h>
 #include <linux/atomic.h>
 #include <asm/vio.h>
@@ -3513,6 +3514,67 @@ static const struct net_device_ops ibmveth_netdev_ops = {
 #endif
 };
 
+static int ibmveth_buffer_pools_show(struct seq_file *m, void *v)
+{
+	struct ibmveth_adapter *adapter = m->private;
+	int i, j;
+
+	/*
+	 * size / buff_size / pool->active are written under RTNL
+	 * (veth_pool_store, open template copy). Take the same lock so
+	 * those columns are not a torn snapshot. available is updated
+	 * from NAPI/softirq; only atomic_read() keeps it from tearing.
+	 * Not required for memory safety; embedded arrays only.
+	 */
+	rtnl_lock();
+
+	seq_puts(m, "Queue  Pool  Count  BuffSize  Active  Available\n");
+	seq_puts(m, "-----  ----  -----  --------  ------  ---------\n");
+	if (!adapter->opened) {
+		seq_puts(m, "# down: Active/Available 0 unless allocated\n");
+		seq_puts(m, "# down: geometry above queue 0 set at open\n");
+	}
+
+	for (i = 0; i < ibmveth_get_num_rx_queues(adapter); i++) {
+		for (j = 0; j < IBMVETH_NUM_BUFF_POOLS; j++) {
+			struct ibmveth_buff_pool *pool =
+				&adapter->rx_buff_pool[i][j];
+			bool live = pool->skbuff && pool->free_map;
+			int active = live ? pool->active : 0;
+			int available = live ? atomic_read(&pool->available)
+					     : 0;
+
+			seq_printf(m, "%5d  %4d  %5u  %8u  %6d  %9d\n",
+				   i, j, pool->size, pool->buff_size,
+				   active, available);
+		}
+	}
+
+	rtnl_unlock();
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(ibmveth_buffer_pools);
+
+/* Driver-owned root so per-adapter dirs use a stable vio name, not the
+ * mutable netdev->name (avoids stale names / eth0 collisions after rename).
+ */
+static struct dentry *ibmveth_dbg_root;
+
+static void ibmveth_debugfs_init(struct ibmveth_adapter *adapter)
+{
+	adapter->debugfs_dir =
+		debugfs_create_dir(dev_name(&adapter->vdev->dev),
+				   ibmveth_dbg_root);
+	debugfs_create_file("buffer_pools", 0400, adapter->debugfs_dir,
+			    adapter, &ibmveth_buffer_pools_fops);
+}
+
+static void ibmveth_debugfs_exit(struct ibmveth_adapter *adapter)
+{
+	debugfs_remove_recursive(adapter->debugfs_dir);
+	adapter->debugfs_dir = NULL;
+}
+
 static void ibmveth_put_pool_kobjs(struct ibmveth_adapter *adapter,
 				   int pools_ready)
 {
@@ -3751,6 +3813,8 @@ static int ibmveth_probe(struct vio_dev *dev, const struct vio_device_id *id)
 
 	netdev_dbg(netdev, "registered\n");
 
+	ibmveth_debugfs_init(adapter);
+
 	return 0;
 }
 
@@ -3760,6 +3824,8 @@ static void ibmveth_remove(struct vio_dev *dev)
 	struct ibmveth_adapter *adapter = netdev_priv(netdev);
 	int i;
 
+	ibmveth_debugfs_exit(adapter);
+
 	for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++)
 		kobject_put(&adapter->rx_buff_pool[0][i].kobj);
 
@@ -3986,15 +4052,27 @@ static struct vio_driver ibmveth_driver = {
 
 static int __init ibmveth_module_init(void)
 {
+	int rc;
+
 	printk(KERN_DEBUG "%s: %s %s\n", ibmveth_driver_name,
 	       ibmveth_driver_string, ibmveth_driver_version);
 
-	return vio_register_driver(&ibmveth_driver);
+	ibmveth_dbg_root = debugfs_create_dir(ibmveth_driver_name, NULL);
+
+	rc = vio_register_driver(&ibmveth_driver);
+	if (rc) {
+		debugfs_remove_recursive(ibmveth_dbg_root);
+		ibmveth_dbg_root = NULL;
+	}
+
+	return rc;
 }
 
 static void __exit ibmveth_module_exit(void)
 {
 	vio_unregister_driver(&ibmveth_driver);
+	debugfs_remove_recursive(ibmveth_dbg_root);
+	ibmveth_dbg_root = NULL;
 }
 
 module_init(ibmveth_module_init);
diff --git a/drivers/net/ethernet/ibm/ibmveth.h b/drivers/net/ethernet/ibm/ibmveth.h
index 0f2971c8627a..1276b3669f2c 100644
--- a/drivers/net/ethernet/ibm/ibmveth.h
+++ b/drivers/net/ethernet/ibm/ibmveth.h
@@ -381,6 +381,8 @@ struct ibmveth_adapter {
 	struct ibmveth_rx_queue_stats *rx_qstats;
 	struct ibmveth_tx_queue_stats *tx_qstats;
 
+	struct dentry *debugfs_dir;
+
 	/* Ethtool settings */
 	u8 duplex;
 	u32 speed;
-- 
2.50.1 (Apple Git-155)