[PATCH 2/7] io_uring/notif: count pending zerocopy notifications per ring

[Jens Axboe <axboe@kernel.dk>]

SEND_ZC notifications are io_kiocbs like any other as far as request
and task accounting goes, but they are special in that they cannot be
canceled and only complete once the network stack is done with the
data. With an unresponsive peer, that can take a while.

The exit and release paths are about to start waiting for requests to
finish so that the files they pin get released in a timely manner, and
notifications neither pin files nor finish in a timely manner. Keep a
per-ring count of them so those paths can leave them out.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 include/linux/io_uring_types.h | 2 ++
 io_uring/notif.c               | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 39629ee77b91..90fea94ad202 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -522,6 +522,8 @@ struct io_ring_ctx {
 
 	/* protected by ->completion_lock */
 	unsigned			nr_req_allocated;
+	/* pending SEND_ZC notifications, protected by ->uring_lock */
+	unsigned			nr_notifs;
 
 #ifdef CONFIG_NET_RX_BUSY_POLL
 	struct list_head	napi_list;	/* track busy poll napi_id */
diff --git a/io_uring/notif.c b/io_uring/notif.c
index efce8ae12eaa..6c49aff515df 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -36,6 +36,7 @@ static void io_notif_tw_complete(struct io_tw_req tw_req, io_tw_token_t tw)
 		}
 
 		nd = nd->next;
+		ctx->nr_notifs--;
 		io_req_task_complete((struct io_tw_req){notif}, tw);
 	} while (nd);
 }
@@ -119,6 +120,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
 
 	if (unlikely(!io_alloc_req(ctx, &notif)))
 		return NULL;
+	ctx->nr_notifs++;
 	notif->ctx = ctx;
 	notif->opcode = IORING_OP_NOP;
 	notif->flags = 0;
-- 
2.55.0