io_uring/net: move mm accounting to a slower path

We can also move mm accounting to the extended callbacks. It removes a
few cycles from the hot path including skipping one function call and
setting io_req_task_complete as a callback directly. For user backed I/O
it shouldn't make any difference taking into considering atomic mm
accounting and page pinning.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1062f270273ad11c1b7b45ec59a6a317533d5e64.1667557923.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/net.c

@@ -1097,6 +1097,7 @@ int io_send_zc(struct io_kiocb *req, unsigned int issue_flags)
 			return ret;
 		msg.sg_from_iter = io_sg_from_iter;
 	} else {
+		io_notif_set_extended(zc->notif);
 		ret = import_single_range(WRITE, zc->buf, zc->len, &iov,
 					  &msg.msg_iter);
 		if (unlikely(ret))
@@ -1158,6 +1159,8 @@ int io_sendmsg_zc(struct io_kiocb *req, unsigned int issue_flags)
 	unsigned flags;
 	int ret, min_ret = 0;
 
+	io_notif_set_extended(sr->notif);
+
 	sock = sock_from_file(req->file);
 	if (unlikely(!sock))
 		return -ENOTSOCK;

io_uring/notif.c

@@ -9,11 +9,14 @@
 #include "notif.h"
 #include "rsrc.h"
 
-static void __io_notif_complete_tw(struct io_kiocb *notif, bool *locked)
+static void io_notif_complete_tw_ext(struct io_kiocb *notif, bool *locked)
 {
 	struct io_notif_data *nd = io_notif_to_data(notif);
 	struct io_ring_ctx *ctx = notif->ctx;
 
+	if (nd->zc_report && (nd->zc_copied || !nd->zc_used))
+		notif->cqe.res |= IORING_NOTIF_USAGE_ZC_COPIED;
+
 	if (nd->account_pages && ctx->user) {
 		__io_unaccount_mem(ctx->user, nd->account_pages);
 		nd->account_pages = 0;
@@ -21,16 +24,6 @@ static void __io_notif_complete_tw(struct io_kiocb *notif, bool *locked)
 	io_req_task_complete(notif, locked);
 }
 
-static void io_notif_complete_tw_ext(struct io_kiocb *notif, bool *locked)
-{
-	struct io_notif_data *nd = io_notif_to_data(notif);
-
-	if (nd->zc_report && (nd->zc_copied || !nd->zc_used))
-		notif->cqe.res |= IORING_NOTIF_USAGE_ZC_COPIED;
-
-	__io_notif_complete_tw(notif, locked);
-}
-
 static void io_tx_ubuf_callback(struct sk_buff *skb, struct ubuf_info *uarg,
 				bool success)
 {
@@ -59,11 +52,14 @@ void io_notif_set_extended(struct io_kiocb *notif)
 {
 	struct io_notif_data *nd = io_notif_to_data(notif);
 
-	nd->zc_report = false;
-	nd->zc_used = false;
-	nd->zc_copied = false;
-	notif->io_task_work.func = io_notif_complete_tw_ext;
-	io_notif_to_data(notif)->uarg.callback = io_tx_ubuf_callback_ext;
+	if (nd->uarg.callback != io_tx_ubuf_callback_ext) {
+		nd->account_pages = 0;
+		nd->zc_report = false;
+		nd->zc_used = false;
+		nd->zc_copied = false;
+		nd->uarg.callback = io_tx_ubuf_callback_ext;
+		notif->io_task_work.func = io_notif_complete_tw_ext;
+	}
 }
 
 struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
@@ -81,10 +77,9 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
 	notif->task = current;
 	io_get_task_refs(1);
 	notif->rsrc_node = NULL;
-	notif->io_task_work.func = __io_notif_complete_tw;
+	notif->io_task_work.func = io_req_task_complete;
 
 	nd = io_notif_to_data(notif);
-	nd->account_pages = 0;
 	nd->uarg.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
 	nd->uarg.callback = io_tx_ubuf_callback;
 	refcount_set(&nd->uarg.refcnt, 1);