linux-kernel - [PATCH 2/2] io_uring: don't trigger timeout with another t-out

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Message-Id: <bcbbaa59d9edd2174c6d6a5303f76dba191b00c8.1587229607.git.asml.silence@gmail.com>
Date:   Sat, 18 Apr 2020 20:20:11 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] io_uring: don't trigger timeout with another t-out

When deciding whether to fire a timeout basing on number of completions,
ignore CQEs emitted by other timeouts.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 fs/io_uring.c | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index c34c5dcc90fc..d72f82c09ce3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1098,33 +1098,20 @@ static void io_kill_timeouts(struct io_ring_ctx *ctx)
 	spin_unlock_irq(&ctx->completion_lock);
 }
 
-static inline bool io_check_in_range(u32 pos, u32 start, u32 end)
-{
-	/* if @end < @start, check for [end, MAX_UINT] + [MAX_UINT, start] */
-	return (pos - start) <= (end - start);
-}
-
 static void __io_flush_timeouts(struct io_ring_ctx *ctx)
 {
-	u32 end, start;
-
-	start = end = ctx->cached_cq_tail;
 	do {
 		struct io_kiocb *req = list_first_entry(&ctx->timeout_list,
 							struct io_kiocb, list);
 
 		if (req->flags & REQ_F_TIMEOUT_NOSEQ)
 			break;
-		/*
-		 * multiple timeouts may have the same target,
-		 * check that @req is in [first_tail, cur_tail]
-		 */
-		if (!io_check_in_range(req->timeout.target_cq, start, end))
+		if (req->timeout.target_cq != ctx->cached_cq_tail
+					- atomic_read(&ctx->cq_timeouts))
 			break;
 
 		list_del_init(&req->list);
 		io_kill_timeout(req);
-		end = ctx->cached_cq_tail;
 	} while (!list_empty(&ctx->timeout_list));
 }
 
@@ -4688,7 +4675,7 @@ static int io_timeout(struct io_kiocb *req)
 		goto add;
 	}
 
-	tail = ctx->cached_cq_tail;
+	tail = ctx->cached_cq_tail - atomic_read(&ctx->cq_timeouts);
 	req->timeout.target_cq = tail + off;
 
 	/*
-- 
2.24.0