io_uring/rsrc: keep cached refs per node

We cache refs of the current node (i.e. ctx->rsrc_node) in
ctx->rsrc_cached_refs. We'll be moving away from atomics, so move the
cached refs in struct io_rsrc_node for now. It's a prep patch and
shouldn't change anything in practise.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9edc3669c1d71b06c2dca78b2b2b8bb9292738b9.1680576071.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/io_uring_types.h

@@ -240,7 +240,6 @@ struct io_ring_ctx {
 		 * uring_lock, and updated through io_uring_register(2)
 		 */
 		struct io_rsrc_node	*rsrc_node;
-		int			rsrc_cached_refs;
 		atomic_t		cancel_seq;
 		struct io_file_table	file_table;
 		unsigned		nr_user_files;

io_uring/rsrc.c

@@ -36,9 +36,11 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
 void io_rsrc_refs_drop(struct io_ring_ctx *ctx)
 	__must_hold(&ctx->uring_lock)
 {
-	if (ctx->rsrc_cached_refs) {
-		io_rsrc_put_node(ctx->rsrc_node, ctx->rsrc_cached_refs);
-		ctx->rsrc_cached_refs = 0;
+	struct io_rsrc_node *node = ctx->rsrc_node;
+
+	if (node && node->cached_refs) {
+		io_rsrc_put_node(node, node->cached_refs);
+		node->cached_refs = 0;
 	}
 }
 
@@ -151,11 +153,11 @@ static void io_buffer_unmap(struct io_ring_ctx *ctx, struct io_mapped_ubuf **slo
 	*slot = NULL;
 }
 
-void io_rsrc_refs_refill(struct io_ring_ctx *ctx)
+void io_rsrc_refs_refill(struct io_ring_ctx *ctx, struct io_rsrc_node *node)
 	__must_hold(&ctx->uring_lock)
 {
-	ctx->rsrc_cached_refs += IO_RSRC_REF_BATCH;
-	refcount_add(IO_RSRC_REF_BATCH, &ctx->rsrc_node->refs);
+	node->cached_refs += IO_RSRC_REF_BATCH;
+	refcount_add(IO_RSRC_REF_BATCH, &node->refs);
 }
 
 static void __io_rsrc_put_work(struct io_rsrc_node *ref_node)
@@ -300,6 +302,7 @@ void io_rsrc_node_switch(struct io_ring_ctx *ctx,
 	if (!ctx->rsrc_node) {
 		ctx->rsrc_node = ctx->rsrc_backup_node;
 		ctx->rsrc_backup_node = NULL;
+		ctx->rsrc_node->cached_refs = 0;
 	}
 }
 

io_uring/rsrc.h

@@ -43,6 +43,7 @@ struct io_rsrc_node {
 	struct io_rsrc_data		*rsrc_data;
 	struct llist_node		llist;
 	bool				done;
+	int				cached_refs;
 };
 
 struct io_mapped_ubuf {
@@ -56,7 +57,7 @@ struct io_mapped_ubuf {
 void io_rsrc_put_tw(struct callback_head *cb);
 void io_rsrc_node_ref_zero(struct io_rsrc_node *node);
 void io_rsrc_put_work(struct work_struct *work);
-void io_rsrc_refs_refill(struct io_ring_ctx *ctx);
+void io_rsrc_refs_refill(struct io_ring_ctx *ctx, struct io_rsrc_node *node);
 void io_wait_rsrc_data(struct io_rsrc_data *data);
 void io_rsrc_node_destroy(struct io_rsrc_node *ref_node);
 void io_rsrc_refs_drop(struct io_ring_ctx *ctx);
@@ -128,17 +129,18 @@ static inline void io_req_put_rsrc_locked(struct io_kiocb *req,
 
 	if (node) {
 		if (node == ctx->rsrc_node)
-			ctx->rsrc_cached_refs++;
+			node->cached_refs++;
 		else
 			io_rsrc_put_node(node, 1);
 	}
 }
 
-static inline void io_charge_rsrc_node(struct io_ring_ctx *ctx)
+static inline void io_charge_rsrc_node(struct io_ring_ctx *ctx,
+				       struct io_rsrc_node *node)
 {
-	ctx->rsrc_cached_refs--;
-	if (unlikely(ctx->rsrc_cached_refs < 0))
-		io_rsrc_refs_refill(ctx);
+	node->cached_refs--;
+	if (unlikely(node->cached_refs < 0))
+		io_rsrc_refs_refill(ctx, node);
 }
 
 static inline void io_req_set_rsrc_node(struct io_kiocb *req,
@@ -151,7 +153,7 @@ static inline void io_req_set_rsrc_node(struct io_kiocb *req,
 		lockdep_assert_held(&ctx->uring_lock);
 
 		req->rsrc_node = ctx->rsrc_node;
-		io_charge_rsrc_node(ctx);
+		io_charge_rsrc_node(ctx, ctx->rsrc_node);
 		io_ring_submit_unlock(ctx, issue_flags);
 	}
 }