Re: [PATCH net-next v3 10/13] 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 | 13 +++++++++++++
 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, 29 insertions(+)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index 85209e19dca9..695e0e4e0d8b 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml

@@ -125,6 +125,18 @@ name: netdev
         type: uint
         doc: |
           Amount of memory held by inflight pages.
+      -
+        name: detach-time
+        type: uint
+        doc: |
+          Seconds in CLOCK_BOOTTIME of when Page Pool was detached by
+          the driver. Once detached Page Pool can no longer be used to
+          allocate memory.
+          Page Pools wait for all the memory allocated from them to be freed
+          before truly disappearing. "Detached" Page Pools cannot be
+          "re-attached", they are just waiting to disappear.
+          Attribute is absent if Page Pool has not been detached, and
+          can still be used to allocate new memory.

 operations:
   list:

@@ -176,6 +188,7 @@ name: netdev
             - napi-id
             - inflight
             - inflight-mem
+            - detach-time
       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..ac286ea8ce2d 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 detach_time;
                u32 napi_id;
                u32 id;
        } user;

diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index 26ae5bdd3187..756410274120 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_DETACH_TIME,

        __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..a821fb5fe054 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_detached(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..90665d40f1eb 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_detached(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..f28ad2179f53 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.detach_time &&
+           nla_put_uint(rsp, NETDEV_A_PAGE_POOL_DETACH_TIME,