[PATCH 4/5] io_uring: support nonblock try for splicing from pipe to pipe

[Hao Xu <hao.xu@linux.dev>]

From: Hao Xu <howeyxu@tencent.com>

splice() in io_uring is running in a slow way since it fully depends on
io workers. While splicing from pipe to pipe is a simpler case compared
with file to pipe and pipe to file. Let's make it support nonblock
first. This way we get a fast path for splicing fom pipe to pipe.

Signed-off-by: Hao Xu <howeyxu@tencent.com>
---
 io_uring/splice.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/io_uring/splice.c b/io_uring/splice.c
index b2cd1044c3ee..650c70e3dde1 100644
--- a/io_uring/splice.c
+++ b/io_uring/splice.c
@@ -88,6 +88,14 @@ int io_splice_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	return __io_splice_prep(req, sqe);
 }
 
+bool io_splice_support_nowait(struct file *in, struct file *out)
+{
+	if (get_pipe_info(in, true) && get_pipe_info(out, true))
+		return true;
+
+	return false;
+}
+
 int io_splice(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct io_splice *sp = io_kiocb_to_cmd(req);
@@ -100,9 +108,6 @@ int io_splice(struct io_kiocb *req, unsigned int issue_flags)
 	if (unlikely(!sp->len))
 		goto done;
 
-	if (issue_flags & IO_URING_F_NONBLOCK)
-		return -EAGAIN;
-
 	if (sp->flags & SPLICE_F_FD_IN_FIXED)
 		in = io_file_get_fixed(req, sp->splice_fd_in, issue_flags);
 	else
@@ -112,6 +117,16 @@ int io_splice(struct io_kiocb *req, unsigned int issue_flags)
 		goto done;
 	}
 
+	if (issue_flags & IO_URING_F_NONBLOCK) {
+		if (io_splice_support_nowait(in, out)) {
+			flags |= SPLICE_F_NONBLOCK;
+		} else {
+			if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
+				io_put_file(in);
+			return -EAGAIN;
+		}
+	}
+
 	poff_in = (sp->off_in == -1) ? NULL : &sp->off_in;
 	poff_out = (sp->off_out == -1) ? NULL : &sp->off_out;
 
@@ -119,6 +134,9 @@ int io_splice(struct io_kiocb *req, unsigned int issue_flags)
 
 	if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
 		io_put_file(in);
+	if (ret == -EAGAIN)
+		return ret;
+
 done:
 	if (ret != sp->len)
 		req_set_fail(req);
-- 
2.25.1