netdev - [PATCH v2 net-next 06/14] af_unix: Bulk update unix_tot_inflight/unix

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Date: Fri, 16 Feb 2024 13:05:48 -0800
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
	<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v2 net-next 06/14] af_unix: Bulk update unix_tot_inflight/unix_inflight when queuing skb.

Currently, we track the number of inflight sockets in two variables.
unix_tot_inflight is the total number of inflight AF_UNIX sockets on
the host, and user->unix_inflight is the number of inflight fds per
user.

We update them one by one in unix_inflight(), which can be done once
in batch.  Also, sendmsg() could fail even after unix_inflight(), then
we need to acquire unix_gc_lock only to decrement the counters.

Let's bulk update the counters in unix_add_edges() and unix_del_edges(),
which is called only for successfully passed fds.

Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/unix/garbage.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 97a43f8ec5a5..93d7760e4ab1 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -111,6 +111,7 @@ void unix_init_vertex(struct unix_sock *u)
 
 DEFINE_SPINLOCK(unix_gc_lock);
 static LIST_HEAD(unix_unvisited_vertices);
+unsigned int unix_tot_inflight;
 
 void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver)
 {
@@ -144,6 +145,9 @@ void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver)
 			list_add_tail(&edge->embryo_entry, &receiver->vertex.edges);
 	}
 
+	WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + fpl->count_unix);
+	WRITE_ONCE(fpl->user->unix_inflight, fpl->user->unix_inflight + fpl->count);
+
 	spin_unlock(&unix_gc_lock);
 
 	fpl->inflight = true;
@@ -164,6 +168,9 @@ void unix_del_edges(struct scm_fp_list *fpl)
 			list_del_init(&edge->predecessor->entry);
 	}
 
+	WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - fpl->count_unix);
+	WRITE_ONCE(fpl->user->unix_inflight, fpl->user->unix_inflight - fpl->count);
+
 	spin_unlock(&unix_gc_lock);
 
 	fpl->inflight = false;
@@ -206,7 +213,6 @@ void unix_free_edges(struct scm_fp_list *fpl)
 	kvfree(fpl->edges);
 }
 
-unsigned int unix_tot_inflight;
 static LIST_HEAD(gc_candidates);
 static LIST_HEAD(gc_inflight_list);
 
@@ -227,13 +233,8 @@ void unix_inflight(struct user_struct *user, struct file *filp)
 			WARN_ON_ONCE(list_empty(&u->link));
 		}
 		u->inflight++;
-
-		/* Paired with READ_ONCE() in wait_for_unix_gc() */
-		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
 	}
 
-	WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
-
 	spin_unlock(&unix_gc_lock);
 }
 
@@ -250,13 +251,8 @@ void unix_notinflight(struct user_struct *user, struct file *filp)
 		u->inflight--;
 		if (!u->inflight)
 			list_del_init(&u->link);
-
-		/* Paired with READ_ONCE() in wait_for_unix_gc() */
-		WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
 	}
 
-	WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
-
 	spin_unlock(&unix_gc_lock);
 }
 
-- 
2.30.2