linux-kernel - [PATCH AUTOSEL 5.5 23/41] io-wq: fix IO_WQ_WORK_NO

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Date:   Sun, 15 Mar 2020 22:33:01 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>,
        io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.5 23/41] io-wq: fix IO_WQ_WORK_NO_CANCEL cancellation

From: Pavel Begunkov <asml.silence@...il.com>

[ Upstream commit fc04c39bae01a607454f7619665309870c60937a ]

To cancel a work, io-wq sets IO_WQ_WORK_CANCEL and executes the
callback. However, IO_WQ_WORK_NO_CANCEL works will just execute and may
return next work, which will be ignored and lost.

Cancel the whole link.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io-wq.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 25ffb6685baea..1f46fe663b287 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -733,6 +733,17 @@ static bool io_wq_can_queue(struct io_wqe *wqe, struct io_wqe_acct *acct,
 	return true;
 }
 
+static void io_run_cancel(struct io_wq_work *work)
+{
+	do {
+		struct io_wq_work *old_work = work;
+
+		work->flags |= IO_WQ_WORK_CANCEL;
+		work->func(&work);
+		work = (work == old_work) ? NULL : work;
+	} while (work);
+}
+
 static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
 {
 	struct io_wqe_acct *acct = io_work_get_acct(wqe, work);
@@ -745,8 +756,7 @@ static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work)
 	 * It's close enough to not be an issue, fork() has the same delay.
 	 */
 	if (unlikely(!io_wq_can_queue(wqe, acct, work))) {
-		work->flags |= IO_WQ_WORK_CANCEL;
-		work->func(&work);
+		io_run_cancel(work);
 		return;
 	}
 
@@ -882,8 +892,7 @@ static enum io_wq_cancel io_wqe_cancel_cb_work(struct io_wqe *wqe,
 	spin_unlock_irqrestore(&wqe->lock, flags);
 
 	if (found) {
-		work->flags |= IO_WQ_WORK_CANCEL;
-		work->func(&work);
+		io_run_cancel(work);
 		return IO_WQ_CANCEL_OK;
 	}
 
@@ -957,8 +966,7 @@ static enum io_wq_cancel io_wqe_cancel_work(struct io_wqe *wqe,
 	spin_unlock_irqrestore(&wqe->lock, flags);
 
 	if (found) {
-		work->flags |= IO_WQ_WORK_CANCEL;
-		work->func(&work);
+		io_run_cancel(work);
 		return IO_WQ_CANCEL_OK;
 	}
 
-- 
2.20.1