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From:   Pavel Begunkov <asml.silence@gmail.com>
To:     Jens Axboe <axboe@kernel.dk>, io-uring@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] io_uring: don't prepare DRAIN reqs twice
Date:   Sun, 17 May 2020 14:02:11 +0300
Message-Id: <bb206ef92fd1323e8adbe7fc71aca019897c9597.1589712727.git.asml.silence@gmail.com>
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If req->io is not NULL, it's already prepared. Don't do it again,
it's dangerous.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5a19120345e4..9e81781d7632 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5098,12 +5098,13 @@ static int io_req_defer(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	if (!req_need_defer(req) && list_empty_careful(&ctx->defer_list))
 		return 0;
 
-	if (!req->io && io_alloc_async_ctx(req))
-		return -EAGAIN;
-
-	ret = io_req_defer_prep(req, sqe);
-	if (ret < 0)
-		return ret;
+	if (!req->io) {
+		if (io_alloc_async_ctx(req))
+			return -EAGAIN;
+		ret = io_req_defer_prep(req, sqe);
+		if (ret < 0)
+			return ret;
+	}
 
 	spin_lock_irq(&ctx->completion_lock);
 	if (!req_need_defer(req) && list_empty(&ctx->defer_list)) {
-- 
2.24.0