在 2021/9/6 下午11:56, Pavel Begunkov 写道:
On 9/3/21 12:00 PM, Hao Xu wrote:
For operations like accept, multishot is a useful feature, since we can
reduce a number of accept sqe. Let's integrate it to fast poll, it may
be good for other operations in the future.
__io_arm_poll_handler() |
-> vfs_poll() |
| io_async_task_func() // post CQE
| ...
| do_apoll_rewait();
-> continues after vfs_poll(),|
removing poll->head of |
the second poll attempt. |
Sorry.. a little bit confused by this case, would you mind explain a bit
more..is the right part a system-workqueue context? and is
do_apoll_rewait() io_poll_rewait() function?
One of the reasons for forbidding multiple apoll's is that it
might be racy. I haven't looked into this implementation, but
we should check if there will be problems from that.
FWIW, putting aside this patchset, the poll/apoll is not in
the best shape and can use some refactoring.
Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
---
fs/io_uring.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d6df60c4cdb9..dae7044e0c24 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5277,8 +5277,15 @@ static void io_async_task_func(struct io_kiocb *req, bool *locked)
return;
}
- hash_del(&req->hash_node);
- io_poll_remove_double(req);
+ if (READ_ONCE(apoll->poll.canceled))
+ apoll->poll.events |= EPOLLONESHOT;
+ if (apoll->poll.events & EPOLLONESHOT) {
+ hash_del(&req->hash_node);
+ io_poll_remove_double(req);
+ } else {
+ add_wait_queue(apoll->poll.head, &apoll->poll.wait);
+ }
+
spin_unlock(&ctx->completion_lock);
if (!READ_ONCE(apoll->poll.canceled))
@@ -5366,7 +5373,7 @@ static int io_arm_poll_handler(struct io_kiocb *req)
struct io_ring_ctx *ctx = req->ctx;
struct async_poll *apoll;
struct io_poll_table ipt;
- __poll_t ret, mask = EPOLLONESHOT | POLLERR | POLLPRI;
+ __poll_t ret, mask = POLLERR | POLLPRI;
int rw;
if (!req->file || !file_can_poll(req->file))
@@ -5388,6 +5395,8 @@ static int io_arm_poll_handler(struct io_kiocb *req)
rw = WRITE;
mask |= POLLOUT | POLLWRNORM;
}
+ if (!(req->flags & REQ_F_APOLL_MULTISHOT))
+ mask |= EPOLLONESHOT;
/* if we can't nonblock try, then no point in arming a poll handler */
if (!io_file_supports_nowait(req, rw))
