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From: Bijan Mottahedeh <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: [RFC 1/1] io_uring: process requests completed with -EAGAIN on poll list
Date: Thu,  2 Apr 2020 11:54:25 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

A request that completes with an -EAGAIN result after it has been added
to the poll list, will not be removed from that list in io_do_iopoll()
because the f_op->iopoll() will not succeed for that request.

Maintain a retryable local list similar to the done list, and explicity
reissue requests with an -EAGAIN result.

Signed-off-by: Bijan Mottahedeh <[email protected]>
---
 fs/io_uring.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 62bd410..a3e3a4e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1738,11 +1738,24 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, unsigned int *nr_events,
 	io_free_req_many(ctx, &rb);
 }
 
+static void io_iopoll_queue(struct list_head *again)
+{
+	struct io_kiocb *req;
+
+	while (!list_empty(again)) {
+		req = list_first_entry(again, struct io_kiocb, list);
+		list_del(&req->list);
+		refcount_inc(&req->refs);
+		io_queue_async_work(req);
+	}
+}
+
 static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
 			long min)
 {
 	struct io_kiocb *req, *tmp;
 	LIST_HEAD(done);
+	LIST_HEAD(again);
 	bool spin;
 	int ret;
 
@@ -1757,9 +1770,9 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
 		struct kiocb *kiocb = &req->rw.kiocb;
 
 		/*
-		 * Move completed entries to our local list. If we find a
-		 * request that requires polling, break out and complete
-		 * the done list first, if we have entries there.
+		 * Move completed and retryable entries to our local lists.
+		 * If we find a request that requires polling, break out
+		 * and complete those lists first, if we have entries there.
 		 */
 		if (req->flags & REQ_F_IOPOLL_COMPLETED) {
 			list_move_tail(&req->list, &done);
@@ -1768,6 +1781,13 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
 		if (!list_empty(&done))
 			break;
 
+		if (req->result == -EAGAIN) {
+			list_move_tail(&req->list, &again);
+			continue;
+		}
+		if (!list_empty(&again))
+			break;
+
 		ret = kiocb->ki_filp->f_op->iopoll(kiocb, spin);
 		if (ret < 0)
 			break;
@@ -1780,6 +1800,9 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, unsigned int *nr_events,
 	if (!list_empty(&done))
 		io_iopoll_complete(ctx, nr_events, &done);
 
+	if (!list_empty(&again))
+		io_iopoll_queue(&again);
+
 	return ret;
 }
 
-- 
1.8.3.1


  reply	other threads:[~2020-04-02 18:54 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-02 18:54 [RFC 0/1] io_uring: process requests completed with -EAGAIN on poll list Bijan Mottahedeh
2020-04-02 18:54 ` Bijan Mottahedeh [this message]
2020-04-03 19:38   ` [RFC 1/1] " Jens Axboe

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