[PATCH net-next v5 13/15] ibmveth: Expose per-queue buffer pool details via debugfs

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

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Add a read-only buffer_pools debugfs file that lists size, buff_size,
active, and available for every RX queue and buffer pool. That is the
MQ diagnostic view (multi-line table), which does not belong in sysfs.

Keep the historical queue-0 poolN sysfs ABI unchanged:

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

Those are one-value-per-file *configuration* knobs for buffer-pool
classes on queue 0, not one directory per RX queue. With MQ, queue 0
pool geometry remains the shared template: open copies it to queues
1..N. Per-queue runtime pressure is what debugfs shows; this series
does not add per-queue pool sysfs dirs.

Unlike ibmvnic (one RX pool per RX queue, sized from firmware, almost
no pool sysfs), ibmveth historically has multiple size-class pools and
already exported poolN via sysfs. Moving only the new all-queue dump
to debugfs matches sysfs "one value per file" review feedback without
breaking that config ABI.

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

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 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 | 69 ++++++++++++++++++++++++++++++
 drivers/net/ethernet/ibm/ibmveth.h |  2 +
 2 files changed, 71 insertions(+)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index 5d4ca4b3d3d0..1b58a3c6ce77 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>
@@ -3421,6 +3422,68 @@ 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;
+
+	/*
+	 * Writers (veth_pool_store, open template copy, reset close/open)
+	 * update these fields under RTNL. Take the same lock so the dump
+	 * is not a torn scalar snapshot. Not required for
+	 * memory safety — embedded arrays only.
+	 */
+	rtnl_lock();
+
+	seq_puts(m, "Queue  Pool  Size  BuffSize  Active  Available\n");
+	seq_puts(m, "-----  ----  ----  --------  ------  ---------\n");
+	if (!adapter->opened)
+		seq_puts(m, "# down: Active/Available 0 unless allocated\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  %4u  %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)
+{
+	if (!ibmveth_dbg_root)
+		ibmveth_dbg_root =
+			debugfs_create_dir(ibmveth_driver_name, NULL);
+
+	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)
 {
@@ -3647,6 +3710,8 @@ 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;
 }
 
@@ -3656,6 +3721,8 @@ 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);
 
@@ -3891,6 +3958,8 @@ static int __init ibmveth_module_init(void)
 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 0960448f53ea..8c826d23ddf4 100644
--- a/drivers/net/ethernet/ibm/ibmveth.h
+++ b/drivers/net/ethernet/ibm/ibmveth.h
@@ -392,6 +392,8 @@ 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)