Re: io_uring: not good enough for release

[Jens Axboe <axboe@kernel.dk>]

On 4/23/19 4:07 PM, Jens Axboe wrote:
>>> (Also RWF_NOWAIT doesn't work in io_uring right now: IOCB_NOWAIT is
>>> always removed in the workqueue context, and I don't see an early EAGAIN
>>> completion).
>>
>> That's a case I didn't consider, that you'd want to see EAGAIN after
>> it's been punted. Once punted, we're not going to return EAGAIN since
>> we can now block. Not sure how you'd want to handle that any better...
> 
> I think I grok this one too now - what you're saying is that if the
> caller has RWF_NOWAIT set, then the EAGAIN should be returned instead of
> being punted to the workqueue? I totally agree with that, that's a bug.

This should do it for the EAGAIN part, if the user has set RWF_NOWAIT
in the sqe, then we don't do the automatic punt to workqueue. We just
return the EAGAIN instead.


diff --git a/fs/io_uring.c b/fs/io_uring.c
index 58ec6e449fd8..6c0d49c3736b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -822,7 +822,7 @@ static int io_prep_rw(struct io_kiocb *req, const struct sqe_submit *s,
 	ret = kiocb_set_rw_flags(kiocb, READ_ONCE(sqe->rw_flags));
 	if (unlikely(ret))
 		return ret;
-	if (force_nonblock) {
+	if (force_nonblock && !(kiocb->ki_flags & IOCB_NOWAIT)) {
 		kiocb->ki_flags |= IOCB_NOWAIT;
 		req->flags |= REQ_F_FORCE_NONBLOCK;
 	}
@@ -1828,7 +1828,7 @@ static int io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s,
 	}
 
 	ret = __io_submit_sqe(ctx, req, s, true);
-	if (ret == -EAGAIN) {
+	if (ret == -EAGAIN && (req->flags & REQ_F_FORCE_NONBLOCK)) {
 		struct io_uring_sqe *sqe_copy;
 
 		sqe_copy = kmalloc(sizeof(*sqe_copy), GFP_KERNEL);

-- 
Jens Axboe