Merge tag 'io_uring-5.7-2020-05-15' of git://git.kernel.dk/linux-block

Pull io_uring fixes from Jens Axboe:
 "Two small fixes that should go into this release:

   - Check and handle zero length splice (Pavel)

   - Fix a regression in this merge window for fixed files used with
     polled block IO"

* tag 'io_uring-5.7-2020-05-15' of git://git.kernel.dk/linux-block:
  io_uring: polled fixed file must go through free iteration
  io_uring: fix zero len do_splice()

fs/io_uring.c

@@ -1394,10 +1394,6 @@ static void io_free_req_many(struct io_ring_ctx *ctx, struct req_batch *rb)
 		for (i = 0; i < rb->to_free; i++) {
 			struct io_kiocb *req = rb->reqs[i];
 
-			if (req->flags & REQ_F_FIXED_FILE) {
-				req->file = NULL;
-				percpu_ref_put(req->fixed_file_refs);
-			}
 			if (req->flags & REQ_F_INFLIGHT)
 				inflight++;
 			__io_req_aux_free(req);
@@ -1670,7 +1666,7 @@ static inline bool io_req_multi_free(struct req_batch *rb, struct io_kiocb *req)
 	if ((req->flags & REQ_F_LINK_HEAD) || io_is_fallback_req(req))
 		return false;
 
-	if (!(req->flags & REQ_F_FIXED_FILE) || req->io)
+	if (req->file || req->io)
 		rb->need_iter++;
 
 	rb->reqs[rb->to_free++] = req;
@@ -2767,16 +2763,19 @@ static int io_splice(struct io_kiocb *req, bool force_nonblock)
 	struct file *out = sp->file_out;
 	unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
 	loff_t *poff_in, *poff_out;
-	long ret;
+	long ret = 0;
 
 	if (force_nonblock)
 		return -EAGAIN;
 
 	poff_in = (sp->off_in == -1) ? NULL : &sp->off_in;
 	poff_out = (sp->off_out == -1) ? NULL : &sp->off_out;
+
+	if (sp->len) {
 		ret = do_splice(in, poff_in, out, poff_out, sp->len, flags);
 		if (force_nonblock && ret == -EAGAIN)
 			return -EAGAIN;
+	}
 
 	io_put_file(req, in, (sp->flags & SPLICE_F_FD_IN_FIXED));
 	req->flags &= ~REQ_F_NEED_CLEANUP;