Re: [PATCH net-next v2 12/15] net: page_pool: report when page pool was destroyed

Report when page pool was destroyed. Together with the inflight
/ memory use reporting this can serve as a replacement for the
warning about leaked page pools we currently print to dmesg.

Example output for a fake leaked page pool using some hacks
in netdevsim (one "live" pool, and one "leaked" on the same dev):

$ ./cli.py --no-schema --spec netlink/specs/netdev.yaml \
            --dump page-pool-get
[{'id': 2, 'ifindex': 3},
  {'id': 1, 'ifindex': 3, 'destroyed': 133, 'inflight': 1}]

Tested-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
  Documentation/netlink/specs/netdev.yaml |  9 +++++++++
  include/net/page_pool/types.h           |  1 +
  include/uapi/linux/netdev.h             |  1 +
  net/core/page_pool.c                    |  1 +
  net/core/page_pool_priv.h               |  1 +
  net/core/page_pool_user.c               | 12 ++++++++++++
  6 files changed, 25 insertions(+)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index 85209e19dca9..8dafa2a8a4dd 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml

@@ -125,6 +125,14 @@ name: netdev
          type: uint
          doc: |
            Amount of memory held by inflight pages.
+      -
+        name: destroyed
+        type: uint
+        doc: |
+          Seconds in CLOCK_BOOTTIME of when Page Pool was destroyed.
+          Page Pools wait for all the memory allocated from them to be freed
+          before truly disappearing.
+          Absent if Page Pool hasn't been destroyed.
  
  operations:
    list:

@@ -176,6 +184,7 @@ name: netdev
              - napi-id
              - inflight
              - inflight-mem
+            - destroyed
        dump:
          reply: *pp-reply
        config-cond: page-pool

diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
index 7e47d7bb2c1e..f0c51ef5e345 100644
--- a/include/net/page_pool/types.h
+++ b/include/net/page_pool/types.h

@@ -193,6 +193,7 @@ struct page_pool {
  	/* User-facing fields, protected by page_pools_lock */
  	struct {
  		struct hlist_node list;
+		u64 destroyed;
  		u32 napi_id;
  		u32 id;
  	} user;

diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 26ae5bdd3187..e5bf66d2aa31 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h

@@ -70,6 +70,7 @@ enum {
  	NETDEV_A_PAGE_POOL_NAPI_ID,
  	NETDEV_A_PAGE_POOL_INFLIGHT,
  	NETDEV_A_PAGE_POOL_INFLIGHT_MEM,
+	NETDEV_A_PAGE_POOL_DESTROYED,
  
  	__NETDEV_A_PAGE_POOL_MAX,
  	NETDEV_A_PAGE_POOL_MAX = (__NETDEV_A_PAGE_POOL_MAX - 1)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 566390759294..0f3f525c457a 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c

@@ -953,6 +953,7 @@ void page_pool_destroy(struct page_pool *pool)
  	if (!page_pool_release(pool))
  		return;
  
+	page_pool_destroyed(pool);

  	pool->defer_start = jiffies;
  	pool->defer_warn  = jiffies + DEFER_WARN_INTERVAL;
  

diff --git a/net/core/page_pool_priv.h b/net/core/page_pool_priv.h
index 72fb21ea1ddc..7fe6f842a270 100644
--- a/net/core/page_pool_priv.h
+++ b/net/core/page_pool_priv.h

@@ -6,6 +6,7 @@
  s32 page_pool_inflight(const struct page_pool *pool, bool strict);
  
  int page_pool_list(struct page_pool *pool);
+void page_pool_destroyed(struct page_pool *pool);
  void page_pool_unlist(struct page_pool *pool);
  
  #endif

diff --git a/net/core/page_pool_user.c b/net/core/page_pool_user.c
index d889b347f8f4..d0f778f358fc 100644
--- a/net/core/page_pool_user.c
+++ b/net/core/page_pool_user.c

@@ -134,6 +134,10 @@ page_pool_nl_fill(struct sk_buff *rsp, const struct page_pool *pool,
  	    nla_put_uint(rsp, NETDEV_A_PAGE_POOL_INFLIGHT_MEM,
  			 inflight * refsz))
  		goto err_cancel;
+	if (pool->user.destroyed &&
+	    nla_put_uint(rsp, NETDEV_A_PAGE_POOL_DESTROYED,
+			 pool->user.destroyed))
+		goto err_cancel;
  
  	genlmsg_end(rsp, hdr);
  

@@ -219,6 +223,14 @@ int page_pool_list(struct page_pool *pool)
  	return err;
  }
  
+void page_pool_destroyed(struct page_pool *pool)
+{
+	mutex_lock(&page_pools_lock);
+	pool->user.destroyed = ktime_get_boottime_seconds();
+	netdev_nl_page_pool_event(pool, NETDEV_CMD_PAGE_POOL_CHANGE_NTF);