io_uring: retry early for reads if we can poll

Most of the logic in io_read() deals with regular files, and in some ways
it would make sense to split the handling into S_IFREG and others. But
at least for retry, we don't need to bother setting up a bunch of state
just to abort in the loop later. In particular, don't bother forcing
setup of async data for a normal non-vectored read when we don't need it.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3d30f7b..4d8366b 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3773,6 +3773,9 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
 
        if (ret == -EAGAIN || (req->flags & REQ_F_REISSUE)) {
                req->flags &= ~REQ_F_REISSUE;
+               /* if we can poll, just do that */
+               if (req->opcode == IORING_OP_READ && file_can_poll(req->file))
+                       return -EAGAIN;
                /* IOPOLL retry should happen for io-wq threads */
                if (!force_nonblock && !(req->ctx->flags & IORING_SETUP_IOPOLL))
                        goto done;