af_unix: Remove io_uring code for GC.

Since commit 705318a99a13 ("io_uring/af_unix: disable sending
io_uring over sockets"), io_uring's unix socket cannot be passed
via SCM_RIGHTS, so it does not contribute to cyclic reference and
no longer be candidate for garbage collection.

Also, commit 6e5e6d274956 ("io_uring: drop any code related to
SCM_RIGHTS") cleaned up SCM_RIGHTS code in io_uring.

Let's do it in AF_UNIX as well by reverting commit 0091bfc81741
("io_uring/af_unix: defer registered files gc to io_uring release")
and commit 10369080454d ("net: reclaim skb->scm_io_uring bit").

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20240129190435.57228-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 2 insertions, 29 deletions

diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index af676bb8fb67..ce5b5f87b16e 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -184,12 +184,10 @@ static bool gc_in_progress;
 
 static void __unix_gc(struct work_struct *work)
 {
-	struct sk_buff *next_skb, *skb;
-	struct unix_sock *u;
-	struct unix_sock *next;
 	struct sk_buff_head hitlist;
-	struct list_head cursor;
+	struct unix_sock *u, *next;
 	LIST_HEAD(not_cycle_list);
+	struct list_head cursor;
 
 	spin_lock(&unix_gc_lock);
 
@@ -269,30 +267,11 @@ static void __unix_gc(struct work_struct *work)
 
 	spin_unlock(&unix_gc_lock);
 
-	/* We need io_uring to clean its registered files, ignore all io_uring
-	 * originated skbs. It's fine as io_uring doesn't keep references to
-	 * other io_uring instances and so killing all other files in the cycle
-	 * will put all io_uring references forcing it to go through normal
-	 * release.path eventually putting registered files.
-	 */
-	skb_queue_walk_safe(&hitlist, skb, next_skb) {
-		if (skb->destructor == io_uring_destruct_scm) {
-			__skb_unlink(skb, &hitlist);
-			skb_queue_tail(&skb->sk->sk_receive_queue, skb);
-		}
-	}
-
 	/* Here we are. Hitlist is filled. Die. */
 	__skb_queue_purge(&hitlist);
 
 	spin_lock(&unix_gc_lock);
 
-	/* There could be io_uring registered files, just push them back to
-	 * the inflight list
-	 */
-	list_for_each_entry_safe(u, next, &gc_candidates, link)
-		list_move_tail(&u->link, &gc_inflight_list);
-
 	/* All candidates should have been detached by now. */
 	WARN_ON_ONCE(!list_empty(&gc_candidates));
 
diff --git a/net/unix/scm.c b/net/unix/scm.c
index 505e56cf02a2..db65b0ab5947 100644
--- a/net/unix/scm.c
+++ b/net/unix/scm.c
@@ -148,9 +148,3 @@ void unix_destruct_scm(struct sk_buff *skb)
 	sock_wfree(skb);
 }
 EXPORT_SYMBOL(unix_destruct_scm);
-
-void io_uring_destruct_scm(struct sk_buff *skb)
-{
-	unix_destruct_scm(skb);
-}
-EXPORT_SYMBOL(io_uring_destruct_scm);