netdev - [RFC v2 19/19] io_uring: optimise task referencing by notifiers

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Date:   Tue, 21 Dec 2021 15:35:41 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     io-uring@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Willem de Bruijn <willemb@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...nel.org>, Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [RFC v2 19/19] io_uring: optimise task referencing by notifiers

Use io_put_task()/etc. infra holding task references for notifiers, so
we can get rid of atomics there.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 fs/io_uring.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ee496b463462..0eadf4ee5402 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2008,7 +2008,7 @@ static void io_uring_tx_zerocopy_callback(struct sk_buff *skb,
 	if (unlikely(!notifier->task))
 		goto fallback;
 
-	put_task_struct(notifier->task);
+	io_put_task(notifier->task, 1);
 	notifier->task = NULL;
 
 	if (!in_interrupt()) {
@@ -2034,7 +2034,8 @@ static inline void __io_tx_kill_notification(struct io_tx_ctx *tx_ctx)
 
 static inline void io_tx_kill_notification(struct io_tx_ctx *tx_ctx)
 {
-	tx_ctx->notifier->task = get_task_struct(current);
+	tx_ctx->notifier->task = current;
+	io_get_task_refs(1);
 	__io_tx_kill_notification(tx_ctx);
 }
 
-- 
2.34.1