[PATCH v3 net-next 04/14] af_unix: Bulk update unix_tot_inflight/unix_inflight when queuing skb.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

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@amazon.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 96d0b1db3638..e8fe08796d02 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -148,6 +148,7 @@ static void unix_free_vertices(struct scm_fp_list *fpl)
 }
 
 DEFINE_SPINLOCK(unix_gc_lock);
+unsigned int unix_tot_inflight;
 
 void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver)
 {
@@ -172,7 +173,10 @@ void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver)
 		unix_add_edge(fpl, edge);
 	} while (i < fpl->count_unix);
 
+	WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + fpl->count_unix);
 out:
+	WRITE_ONCE(fpl->user->unix_inflight, fpl->user->unix_inflight + fpl->count);
+
 	spin_unlock(&unix_gc_lock);
 
 	fpl->inflight = true;
@@ -195,7 +199,10 @@ void unix_del_edges(struct scm_fp_list *fpl)
 		unix_del_edge(fpl, edge);
 	} while (i < fpl->count_unix);
 
+	WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - fpl->count_unix);
 out:
+	WRITE_ONCE(fpl->user->unix_inflight, fpl->user->unix_inflight - fpl->count);
+
 	spin_unlock(&unix_gc_lock);
 
 	fpl->inflight = false;
@@ -238,7 +245,6 @@ void unix_destroy_fpl(struct scm_fp_list *fpl)
 	unix_free_vertices(fpl);
 }
 
-unsigned int unix_tot_inflight;
 static LIST_HEAD(gc_candidates);
 static LIST_HEAD(gc_inflight_list);
 
@@ -259,13 +265,8 @@ 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);
 }
 
@@ -282,13 +283,8 @@ 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