linux-kernel - [PATCH v6.6 10/26] af_unix: Bulk update unix_tot_inflight/unix

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Message-ID: <20250521144803.2050504-11-lee@kernel.org>
Date: Wed, 21 May 2025 14:45:18 +0000
From: Lee Jones <lee@...nel.org>
To: lee@...nel.org,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Kuniyuki Iwashima <kuniyu@...zon.com>,
	Jens Axboe <axboe@...nel.dk>,
	Sasha Levin <sashal@...nel.org>,
	Michal Luczaj <mhal@...x.co>,
	Rao Shoaib <Rao.Shoaib@...cle.com>,
	Pavel Begunkov <asml.silence@...il.com>,
	linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Cc: stable@...r.kernel.org
Subject: [PATCH v6.6 10/26] af_unix: Bulk update unix_tot_inflight/unix_inflight when queuing skb.

From: Kuniyuki Iwashima <kuniyu@...zon.com>

[ Upstream commit 22c3c0c52d32f41cc38cd936ea0c93f22ced3315 ]

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>
Acked-by: Paolo Abeni <pabeni@...hat.com>
Link: https://lore.kernel.org/r/20240325202425.60930-5-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
(cherry picked from commit 22c3c0c52d32f41cc38cd936ea0c93f22ced3315)
Signed-off-by: Lee Jones <lee@...nel.org>
---
 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 b5b4a200dbf3b..f7041fc230008 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -144,6 +144,7 @@ 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)
 {
@@ -168,7 +169,10 @@ 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;
@@ -191,7 +195,10 @@ 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;
@@ -234,7 +241,6 @@ 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);
 
@@ -255,13 +261,8 @@ 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);
 }
 
@@ -278,13 +279,8 @@ 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);
 }
 
-- 
2.49.0.1112.g889b7c5bd8-goog