io_uring: fix req->apoll_events

apoll_events should be set once in the beginning of poll arming just as
poll->events and not change after. However, currently io_uring resets it
on each __io_poll_execute() for no clear reason. There is also a place
in __io_arm_poll_handler() where we add EPOLLONESHOT to downgrade a
multishot, but forget to do the same thing with ->apoll_events, which is
buggy.

Fixes: 81459350d581e ("io_uring: cache req->apoll->events in req->cflags")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Hao Xu <howeyxu@tencent.com>
Link: https://lore.kernel.org/r/0aef40399ba75b1a4d2c2e85e6e8fd93c02fc6e4.1655814213.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 05508fe..dffa85d 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6950,7 +6950,8 @@ static void io_apoll_task_func(struct io_kiocb *req, bool *locked)
                io_req_complete_failed(req, ret);
 }
 
-static void __io_poll_execute(struct io_kiocb *req, int mask, __poll_t events)
+static void __io_poll_execute(struct io_kiocb *req, int mask,
+                             __poll_t __maybe_unused events)
 {
        req->cqe.res = mask;
        /*
@@ -6959,7 +6960,6 @@ static void __io_poll_execute(struct io_kiocb *req, int mask, __poll_t events)
         * CPU. We want to avoid pulling in req->apoll->events for that
         * case.
         */
-       req->apoll_events = events;
        if (req->opcode == IORING_OP_POLL_ADD)
                req->io_task_work.func = io_poll_task_func;
        else
@@ -7110,6 +7110,8 @@ static int __io_arm_poll_handler(struct io_kiocb *req,
        io_init_poll_iocb(poll, mask, io_poll_wake);
        poll->file = req->file;
 
+       req->apoll_events = poll->events;
+
        ipt->pt._key = mask;
        ipt->req = req;
        ipt->error = 0;
@@ -7140,8 +7142,10 @@ static int __io_arm_poll_handler(struct io_kiocb *req,
 
        if (mask) {
                /* can't multishot if failed, just queue the event we've got */
-               if (unlikely(ipt->error || !ipt->nr_entries))
+               if (unlikely(ipt->error || !ipt->nr_entries)) {
                        poll->events |= EPOLLONESHOT;
+                       req->apoll_events |= EPOLLONESHOT;
+               }
                __io_poll_execute(req, mask, poll->events);
                return 0;
        }
@@ -7388,7 +7392,7 @@ static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
                return -EINVAL;
 
        io_req_set_refcount(req);
-       req->apoll_events = poll->events = io_poll_parse_events(sqe, flags);
+       poll->events = io_poll_parse_events(sqe, flags);
        return 0;
 }