[PATCH v6 1/5] io_uring/zcrx: count zcrx users

[David Wei <dw@davidwei.uk>]

From: Pavel Begunkov <asml.silence@gmail.com>

zcrx tries to detach ifq / terminate page pools when the io_uring ctx
owning it is being destroyed. There will be multiple io_uring instances
attached to it in the future, so add a separate counter to track the
users. Note, refs can't be reused for this purpose as it only used to
prevent zcrx and rings destruction, and also used by page pools to keep
it alive.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: David Wei <dw@davidwei.uk>
---
 io_uring/zcrx.c | 7 +++++--
 io_uring/zcrx.h | 2 ++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 5f7a1b29842e..de4ba6e61130 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -482,6 +482,7 @@ static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
 	spin_lock_init(&ifq->rq_lock);
 	mutex_init(&ifq->pp_lock);
 	refcount_set(&ifq->refs, 1);
+	refcount_set(&ifq->user_refs, 1);
 	return ifq;
 }
 
@@ -742,8 +743,10 @@ void io_unregister_zcrx_ifqs(struct io_ring_ctx *ctx)
 		if (!ifq)
 			break;
 
-		io_close_queue(ifq);
-		io_zcrx_scrub(ifq);
+		if (refcount_dec_and_test(&ifq->user_refs)) {
+			io_close_queue(ifq);
+			io_zcrx_scrub(ifq);
+		}
 		io_put_zcrx_ifq(ifq);
 	}
 
diff --git a/io_uring/zcrx.h b/io_uring/zcrx.h
index f29edc22c91f..32ab95b2cb81 100644
--- a/io_uring/zcrx.h
+++ b/io_uring/zcrx.h
@@ -55,6 +55,8 @@ struct io_zcrx_ifq {
 	struct net_device		*netdev;
 	netdevice_tracker		netdev_tracker;
 	refcount_t			refs;
+	/* counts userspace facing users like io_uring */
+	refcount_t			user_refs;
 
 	/*
 	 * Page pool and net configuration lock, can be taken deeper in the
-- 
2.47.3