On 9/2/20 9:26 AM, Pavel Begunkov wrote: > On 02/09/2020 17:45, Jens Axboe wrote: >> On 9/2/20 4:09 AM, Norman Maurer wrote: >>> Hi there, >>> >>> We are currently working on integrating io_uring into netty and found >>> some “suprising” behaviour which seems like a bug to me. >>> >>> When a socket is marked as non blocking (accepted with O_NONBLOCK flag >>> set) and there is no data to be read IORING_OP_READ should complete >>> directly with EAGAIN or EWOULDBLOCK. This is not the case and it >>> basically blocks forever until there is some data to read. Is this >>> expected ? >>> >>> This seems to be somehow related to a bug that was fixed for >>> IO_URING_ACCEPT with non blocking sockets: >>> >>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.8&id=e697deed834de15d2322d0619d51893022c90ea2 >> >> I agree with you that this is a bug, in general it's useful (and >> expected) that we'd return -EAGAIN for that case. I'll take a look. >> > > That's I mentioned that doing retries for nonblock requests in > io_wq_submit_work() doesn't look consistent. I think killing it > off may help. Right, we should not retry those _in general_, the exception is regular files or block devices to handle IOPOLL retry where we do need it. The below is what I came up with for this one. Might not hurt to make this more explicit for 5.10. commit c78e0f02c3861b5b176b2f79552677b3604deb76 Author: Jens Axboe <axboe@xxxxxxxxx> Date: Wed Sep 2 09:30:31 2020 -0600 io_uring: no read-retry on -EAGAIN error and O_NONBLOCK marked file Actually two things that need fixing up here: - The io_rw_reissue() -EAGAIN retry is explicit to block devices and regular files, so don't ever attempt to do that on other types of files. - If we hit -EAGAIN on a nonblock marked file, don't arm poll handler for it. It should just complete with -EAGAIN. Cc: stable@xxxxxxxxxxxxxxx Reported-by: Norman Maurer <norman.maurer@xxxxxxxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> diff --git a/fs/io_uring.c b/fs/io_uring.c index b1ccd7072d93..dc27cd5b8ad6 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2300,8 +2300,11 @@ static bool io_resubmit_prep(struct io_kiocb *req, int error) static bool io_rw_reissue(struct io_kiocb *req, long res) { #ifdef CONFIG_BLOCK + umode_t mode = file_inode(req->file)->i_mode; int ret; + if (!S_ISBLK(mode) && !S_ISREG(mode)) + return false; if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker()) return false; @@ -3146,6 +3149,9 @@ static int io_read(struct io_kiocb *req, bool force_nonblock, /* IOPOLL retry should happen for io-wq threads */ if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL)) goto done; + /* no retry on NONBLOCK marked file */ + if (kiocb->ki_flags & IOCB_NOWAIT) + goto done; /* some cases will consume bytes even on error returns */ iov_iter_revert(iter, iov_count - iov_iter_count(iter)); ret = io_setup_async_rw(req, iovec, inline_vecs, iter, false); -- Jens Axboe
