[PATCH rdma-next v3] RDMA/nldev: add resource summary max values for usage display

[Tao Cui <cui.tao@linux.dev>]

From: Tao Cui <cuitao@kylinos.cn>

Add RDMA_NLDEV_ATTR_RES_SUMMARY_ENTRY_MAX netlink attribute to expose
device resource limits (max_qp, max_cq, max_mr, max_pd, max_srq) in
the resource summary alongside the existing current count. This allows
userspace tools like iproute2's rdma to display resource usage in
curr/max format.

Expected output from "rdma resource show":
  Before: 0: mlx5_0: qp 123  cq 45  mr 200  pd 10
  After:  0: mlx5_0: qp 123/131072  cq 45/65536  mr 200/1000000  pd 10/32768

In JSON output, both "curr" and "max" fields will be provided so that
scripts can compute percentages if needed.

The new attribute is optional and backward compatible - old userspace
tools will simply ignore it.

Signed-off-by: Tao Cui <cuitao@kylinos.cn>

--
Changes in v3:
- Omit RES_SUMMARY_ENTRY_MAX for resources without an upper bound (cm_id,
  ctx) rather than advertising 0, and leave rendering to userspace.
---
 drivers/infiniband/core/nldev.c  | 29 ++++++++++++++++++++++++++---
 include/uapi/rdma/rdma_netlink.h |  5 +++++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
index 02a0a9c0a4a6..bf6ce2b8db6a 100644
--- a/drivers/infiniband/core/nldev.c
+++ b/drivers/infiniband/core/nldev.c
@@ -188,6 +188,7 @@ static const struct nla_policy nldev_policy[RDMA_NLDEV_ATTR_MAX] = {
 	[RDMA_NLDEV_ATTR_FRMR_POOLS_AGING_PERIOD] = { .type = NLA_U32 },
 	[RDMA_NLDEV_ATTR_FRMR_POOL_PINNED_HANDLES] = { .type = NLA_U32 },
 	[RDMA_NLDEV_ATTR_FRMR_POOL_KEY_KERNEL_VENDOR_KEY] = { .type = NLA_U64 },
+	[RDMA_NLDEV_ATTR_RES_SUMMARY_ENTRY_MAX]	= { .type = NLA_U64 },
 };
 
 static int put_driver_name_print_type(struct sk_buff *msg, const char *name,
@@ -413,7 +414,7 @@ static int fill_port_info(struct sk_buff *msg,
 }
 
 static int fill_res_info_entry(struct sk_buff *msg,
-			       const char *name, u64 curr)
+			       const char *name, u64 curr, u64 max)
 {
 	struct nlattr *entry_attr;
 
@@ -427,6 +428,9 @@ static int fill_res_info_entry(struct sk_buff *msg,
 	if (nla_put_u64_64bit(msg, RDMA_NLDEV_ATTR_RES_SUMMARY_ENTRY_CURR, curr,
 			      RDMA_NLDEV_ATTR_PAD))
 		goto err;
+	if (max && nla_put_u64_64bit(msg, RDMA_NLDEV_ATTR_RES_SUMMARY_ENTRY_MAX, max,
+			      RDMA_NLDEV_ATTR_PAD))
+		goto err;
 
 	nla_nest_end(msg, entry_attr);
 	return 0;
@@ -450,7 +454,7 @@ static int fill_res_info(struct sk_buff *msg, struct ib_device *device,
 	};
 
 	struct nlattr *table_attr;
-	int ret, i, curr;
+	int ret, i, curr, max = 0;
 
 	if (fill_nldev_handle(msg, device))
 		return -EMSGSIZE;
@@ -463,7 +467,26 @@ static int fill_res_info(struct sk_buff *msg, struct ib_device *device,
 		if (!names[i])
 			continue;
 		curr = rdma_restrack_count(device, i, show_details);
-		ret = fill_res_info_entry(msg, names[i], curr);
+		switch (i) {
+		case RDMA_RESTRACK_QP:
+			max = device->attrs.max_qp;
+			break;
+		case RDMA_RESTRACK_CQ:
+			max = device->attrs.max_cq;
+			break;
+		case RDMA_RESTRACK_MR:
+			max = device->attrs.max_mr;
+			break;
+		case RDMA_RESTRACK_PD:
+			max = device->attrs.max_pd;
+			break;
+		case RDMA_RESTRACK_SRQ:
+			max = device->attrs.max_srq;
+			break;
+		default:
+			max = 0;
+		}
+		ret = fill_res_info_entry(msg, names[i], curr, max);
 		if (ret)
 			goto err;
 	}
diff --git a/include/uapi/rdma/rdma_netlink.h b/include/uapi/rdma/rdma_netlink.h
index aac9782ddc09..3af946ecbac3 100644
--- a/include/uapi/rdma/rdma_netlink.h
+++ b/include/uapi/rdma/rdma_netlink.h
@@ -604,6 +604,11 @@ enum rdma_nldev_attr {
 	RDMA_NLDEV_ATTR_FRMR_POOL_PINNED_HANDLES,	/* u32 */
 	RDMA_NLDEV_ATTR_FRMR_POOL_KEY_KERNEL_VENDOR_KEY,	/* u64 */
 
+	/*
+	 * Resource summary entry maximum value.
+	 */
+	RDMA_NLDEV_ATTR_RES_SUMMARY_ENTRY_MAX,		/* u64 */
+
 	/*
 	 * Always the end
 	 */
-- 
2.43.0