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From:   Pavel Begunkov <asml.silence@gmail.com>
To:     io-uring@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     "David S . Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        Willem de Bruijn <willemb@google.com>,
        Jens Axboe <axboe@kernel.dk>, David Ahern <dsahern@kernel.org>,
        kernel-team@fb.com, Pavel Begunkov <asml.silence@gmail.com>
Subject: [PATCH net-next v4 17/27] io_uring: add rsrc referencing for notifiers
Date:   Thu,  7 Jul 2022 12:49:48 +0100
Message-Id: <f9d58e980c64be93300fc345c7714f1e50ab9eae.1657194434.git.asml.silence@gmail.com>
In-Reply-To: <cover.1657194434.git.asml.silence@gmail.com>
References: <cover.1657194434.git.asml.silence@gmail.com>
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In preparation to zerocopy sends with fixed buffers make notifiers to
reference the rsrc node to protect the used fixed buffers. We can't just
grab it for a send request as notifiers can likely outlive requests that
used it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/notif.c |  5 +++++
 io_uring/notif.h |  1 +
 io_uring/rsrc.h  | 12 +++++++++---
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/io_uring/notif.c b/io_uring/notif.c
index aec74f88fc33..0a2e98bd74f6 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -7,10 +7,12 @@
 
 #include "io_uring.h"
 #include "notif.h"
+#include "rsrc.h"
 
 static void __io_notif_complete_tw(struct callback_head *cb)
 {
 	struct io_notif *notif = container_of(cb, struct io_notif, task_work);
+	struct io_rsrc_node *rsrc_node = notif->rsrc_node;
 	struct io_ring_ctx *ctx = notif->ctx;
 
 	if (likely(notif->task)) {
@@ -25,6 +27,7 @@ static void __io_notif_complete_tw(struct callback_head *cb)
 	ctx->notif_locked_nr++;
 	io_cq_unlock_post(ctx);
 
+	io_rsrc_put_node(rsrc_node, 1);
 	percpu_ref_put(&ctx->refs);
 }
 
@@ -119,6 +122,8 @@ struct io_notif *io_alloc_notif(struct io_ring_ctx *ctx,
 	/* master ref owned by io_notif_slot, will be dropped on flush */
 	refcount_set(&notif->uarg.refcnt, 1);
 	percpu_ref_get(&ctx->refs);
+	notif->rsrc_node = ctx->rsrc_node;
+	io_charge_rsrc_node(ctx);
 	return notif;
 }
 
diff --git a/io_uring/notif.h b/io_uring/notif.h
index 23ca7620fff9..1dd48efb7744 100644
--- a/io_uring/notif.h
+++ b/io_uring/notif.h
@@ -10,6 +10,7 @@
 struct io_notif {
 	struct ubuf_info	uarg;
 	struct io_ring_ctx	*ctx;
+	struct io_rsrc_node	*rsrc_node;
 
 	/* complete via tw if ->task is non-NULL, fallback to wq otherwise */
 	struct task_struct	*task;
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index 87f58315b247..af342fd239d0 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -135,6 +135,13 @@ static inline void io_req_put_rsrc_locked(struct io_kiocb *req,
 	}
 }
 
+static inline void io_charge_rsrc_node(struct io_ring_ctx *ctx)
+{
+	ctx->rsrc_cached_refs--;
+	if (unlikely(ctx->rsrc_cached_refs < 0))
+		io_rsrc_refs_refill(ctx);
+}
+
 static inline void io_req_set_rsrc_node(struct io_kiocb *req,
 					struct io_ring_ctx *ctx,
 					unsigned int issue_flags)
@@ -144,9 +151,8 @@ static inline void io_req_set_rsrc_node(struct io_kiocb *req,
 
 		if (!(issue_flags & IO_URING_F_UNLOCKED)) {
 			lockdep_assert_held(&ctx->uring_lock);
-			ctx->rsrc_cached_refs--;
-			if (unlikely(ctx->rsrc_cached_refs < 0))
-				io_rsrc_refs_refill(ctx);
+
+			io_charge_rsrc_node(ctx);
 		} else {
 			percpu_ref_get(&req->rsrc_node->refs);
 		}
-- 
2.36.1