linux-kernel - [RFC net-next io_uring 09/11] io_uring/notif: add helper for flushing refs

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Date:   Wed, 10 Aug 2022 16:49:17 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     io-uring@...r.kernel.org, netdev@...r.kernel.org
Cc:     Jens Axboe <axboe@...nel.dk>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, kernel-team@...com,
        linux-kernel@...r.kernel.org, xen-devel@...ts.xenproject.org,
        Wei Liu <wei.liu@...nel.org>, Paul Durrant <paul@....org>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [RFC net-next io_uring 09/11] io_uring/notif: add helper for flushing refs

Add a helper for dropping notification references during flush. It's a
preparation patch, currently it's only one master ref, but we're going
to add ref caching.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 io_uring/notif.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/io_uring/notif.c b/io_uring/notif.c
index a2ba1e35a59f..5661681b3b44 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -73,6 +73,13 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx,
 	return notif;
 }
 
+static inline bool io_notif_drop_refs(struct io_notif_data *nd)
+{
+	int refs = 1;
+
+	return refcount_sub_and_test(refs, &nd->uarg.refcnt);
+}
+
 void io_notif_slot_flush(struct io_notif_slot *slot)
 	__must_hold(&ctx->uring_lock)
 {
@@ -81,8 +88,7 @@ void io_notif_slot_flush(struct io_notif_slot *slot)
 
 	slot->notif = NULL;
 
-	/* drop slot's master ref */
-	if (refcount_dec_and_test(&nd->uarg.refcnt))
+	if (io_notif_drop_refs(nd))
 		io_notif_complete(notif);
 }
 
@@ -97,13 +103,11 @@ __cold int io_notif_unregister(struct io_ring_ctx *ctx)
 	for (i = 0; i < ctx->nr_notif_slots; i++) {
 		struct io_notif_slot *slot = &ctx->notif_slots[i];
 		struct io_kiocb *notif = slot->notif;
-		struct io_notif_data *nd;
 
 		if (!notif)
 			continue;
-		nd = io_kiocb_to_cmd(notif);
 		slot->notif = NULL;
-		if (!refcount_dec_and_test(&nd->uarg.refcnt))
+		if (!io_notif_drop_refs(io_kiocb_to_cmd(notif)))
 			continue;
 		notif->io_task_work.func = __io_notif_complete_tw;
 		io_req_task_work_add(notif);
-- 
2.37.0