Patch "io_uring: allow re-poll if we made progress" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    io_uring: allow re-poll if we made progress

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     io_uring-allow-re-poll-if-we-made-progress.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit cb51b731674894f54045c3cd6ebab80e2a89af07
Author: Jens Axboe <axboe@xxxxxxxxx>
Date:   Sat Jan 21 10:39:22 2023 -0700

    io_uring: allow re-poll if we made progress
    
    commit 10c873334febaeea9aa0c25c10b5ac0951b77a5f upstream.
    
    We currently check REQ_F_POLLED before arming async poll for a
    notification to retry. If it's set, then we don't allow poll and will
    punt to io-wq instead. This is done to prevent a situation where a buggy
    driver will repeatedly return that there's space/data available yet we
    get -EAGAIN.
    
    However, if we already transferred data, then it should be safe to rely
    on poll again. Gate the check on whether or not REQ_F_PARTIAL_IO is
    also set.
    
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 75d833269751..cc8e13de5fa9 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -5694,7 +5694,7 @@ static int io_arm_poll_handler(struct io_kiocb *req)
 
 	if (!req->file || !file_can_poll(req->file))
 		return IO_APOLL_ABORTED;
-	if (req->flags & REQ_F_POLLED)
+	if ((req->flags & (REQ_F_POLLED|REQ_F_PARTIAL_IO)) == REQ_F_POLLED)
 		return IO_APOLL_ABORTED;
 	if (!def->pollin && !def->pollout)
 		return IO_APOLL_ABORTED;
@@ -5710,7 +5710,10 @@ static int io_arm_poll_handler(struct io_kiocb *req)
 		mask |= POLLOUT | POLLWRNORM;
 	}
 
-	apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
+	if (req->flags & REQ_F_POLLED)
+		apoll = req->apoll;
+	else
+		apoll = kmalloc(sizeof(*apoll), GFP_ATOMIC);
 	if (unlikely(!apoll))
 		return IO_APOLL_ABORTED;
 	apoll->double_poll = NULL;