linux-kernel - [PATCH 1/3] io_uring/net: only import send

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Message-ID: <20250321184819.3847386-2-csander@purestorage.com>
Date: Fri, 21 Mar 2025 12:48:17 -0600
From: Caleb Sander Mateos <csander@...estorage.com>
To: Jens Axboe <axboe@...nel.dk>,
	Pavel Begunkov <asml.silence@...il.com>,
	Ming Lei <ming.lei@...hat.com>,
	Keith Busch <kbusch@...nel.org>,
	Christoph Hellwig <hch@....de>,
	Sagi Grimberg <sagi@...mberg.me>
Cc: Xinyu Zhang <xizhang@...estorage.com>,
	io-uring@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-nvme@...ts.infradead.org,
	Caleb Sander Mateos <csander@...estorage.com>
Subject: [PATCH 1/3] io_uring/net: only import send_zc buffer once

io_send_zc() guards its call to io_send_zc_import() with if (!done_io)
in an attempt to avoid calling it redundantly on the same req. However,
if the initial non-blocking issue returns -EAGAIN, done_io will stay 0.
This causes the subsequent issue to unnecessarily re-import the buffer.

Add an explicit flag "imported" to io_sr_msg to track if its buffer has
already been imported. Clear the flag in io_send_zc_prep(). Call
io_send_zc_import() and set the flag in io_send_zc() if it is unset.

Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
Fixes: 54cdcca05abd ("io_uring/net: switch io_send() and io_send_zc() to using io_async_msghdr")
---
 io_uring/net.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/io_uring/net.c b/io_uring/net.c
index 6d13d378358b..a29893d567b8 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -74,10 +74,11 @@ struct io_sr_msg {
 	unsigned			nr_multishot_loops;
 	u16				flags;
 	/* initialised and used only by !msg send variants */
 	u16				buf_group;
 	bool				retry;
+	bool				imported; /* only for io_send_zc */
 	void __user			*msg_control;
 	/* used only for send zerocopy */
 	struct io_kiocb 		*notif;
 };
 
@@ -1222,10 +1223,11 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_kiocb *notif;
 
 	zc->done_io = 0;
 	zc->retry = false;
+	zc->imported = false;
 	req->flags |= REQ_F_POLL_NO_LAZY;
 
 	if (unlikely(READ_ONCE(sqe->__pad2[0]) || READ_ONCE(sqe->addr3)))
 		return -EINVAL;
 	/* we don't support IOSQE_CQE_SKIP_SUCCESS just yet */
@@ -1369,11 +1371,12 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
 
 	if (!(req->flags & REQ_F_POLLED) &&
 	    (zc->flags & IORING_RECVSEND_POLL_FIRST))
 		return -EAGAIN;
 
-	if (!zc->done_io) {
+	if (!zc->imported) {
+		zc->imported = true;
 		ret = io_send_zc_import(req, issue_flags);
 		if (unlikely(ret))
 			return ret;
 	}
 
-- 
2.45.2