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@purestorage.com>
Fixes: 54cdcca05abd ("io_uring/net: switch io_send() and io_send_zc() to using io_async_msghdr")
Link: https://lore.kernel.org/r/20250321184819.3847386-2-csander@purestorage.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/net.c b/io_uring/net.c
index 1e36a72e4008d251f4cc62c78c60d1e409d748da..030b76e6f6f8826ab5c2a83b533a034da6622937 100644 (file)
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -77,6 +77,7 @@ struct io_sr_msg {
        /* 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;
@@ -1306,6 +1307,7 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
        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)))
@@ -1451,7 +1453,8 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
            (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;