io_uring: combine buffer lookup and import

Registered buffer are currently imported in two steps, first we lookup
a rsrc node and then use it to set up the iterator. The first part is
usually done at the prep stage, and import happens whenever it's needed.
As we want to defer binding to a node so that it works with linked
requests, combine both steps into a single helper.

Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250224213116.3509093-6-kbusch@meta.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

5 files changed, 42 insertions, 51 deletions

diff --git a/io_uring/net.c b/io_uring/net.c
index 22fa1664a6b1..3d93af98967a 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1357,24 +1357,10 @@ static int io_send_zc_import(struct io_kiocb *req, unsigned int issue_flags)
 	int ret;
 
 	if (sr->flags & IORING_RECVSEND_FIXED_BUF) {
-		struct io_ring_ctx *ctx = req->ctx;
-		struct io_rsrc_node *node;
-
-		ret = -EFAULT;
-		io_ring_submit_lock(ctx, issue_flags);
-		node = io_rsrc_node_lookup(&ctx->buf_table, req->buf_index);
-		if (node) {
-			io_req_assign_buf_node(sr->notif, node);
-			ret = 0;
-		}
-		io_ring_submit_unlock(ctx, issue_flags);
-
-		if (unlikely(ret))
-			return ret;
-
-		ret = io_import_fixed(ITER_SOURCE, &kmsg->msg.msg_iter,
-					node->buf, (u64)(uintptr_t)sr->buf,
-					sr->len);
+		sr->notif->buf_index = req->buf_index;
+		ret = io_import_reg_buf(sr->notif, &kmsg->msg.msg_iter,
+					(u64)(uintptr_t)sr->buf, sr->len,
+					ITER_SOURCE, issue_flags);
 		if (unlikely(ret))
 			return ret;
 		kmsg->msg.sg_from_iter = io_sg_from_iter;
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index f3a41132a966..6cf7dba44d5b 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -857,7 +857,7 @@ int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
 	return ret;
 }
 
-int io_import_fixed(int ddir, struct iov_iter *iter,
+static int io_import_fixed(int ddir, struct iov_iter *iter,
 			   struct io_mapped_ubuf *imu,
 			   u64 buf_addr, size_t len)
 {
@@ -916,6 +916,35 @@ int io_import_fixed(int ddir, struct iov_iter *iter,
 	return 0;
 }
 
+static inline struct io_rsrc_node *io_find_buf_node(struct io_kiocb *req,
+						    unsigned issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_rsrc_node *node;
+
+	if (req->flags & REQ_F_BUF_NODE)
+		return req->buf_node;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	node = io_rsrc_node_lookup(&ctx->buf_table, req->buf_index);
+	if (node)
+		io_req_assign_buf_node(req, node);
+	io_ring_submit_unlock(ctx, issue_flags);
+	return node;
+}
+
+int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,
+			u64 buf_addr, size_t len, int ddir,
+			unsigned issue_flags)
+{
+	struct io_rsrc_node *node;
+
+	node = io_find_buf_node(req, issue_flags);
+	if (!node)
+		return -EFAULT;
+	return io_import_fixed(ddir, iter, node->buf, buf_addr, len);
+}
+
 /* Lock two rings at once. The rings must be different! */
 static void lock_two_rings(struct io_ring_ctx *ctx1, struct io_ring_ctx *ctx2)
 {
diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index a6d883c62b22..ce199eb0ac9f 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -50,9 +50,9 @@ void io_free_rsrc_node(struct io_ring_ctx *ctx, struct io_rsrc_node *node);
 void io_rsrc_data_free(struct io_ring_ctx *ctx, struct io_rsrc_data *data);
 int io_rsrc_data_alloc(struct io_rsrc_data *data, unsigned nr);
 
-int io_import_fixed(int ddir, struct iov_iter *iter,
-			   struct io_mapped_ubuf *imu,
-			   u64 buf_addr, size_t len);
+int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,
+			u64 buf_addr, size_t len, int ddir,
+			unsigned issue_flags);
 
 int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg);
 int io_sqe_buffers_unregister(struct io_ring_ctx *ctx);
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 10a4a95ada02..ae44d7e5d200 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -342,8 +342,6 @@ static int io_prep_rw_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe
 			    int ddir)
 {
 	struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
-	struct io_ring_ctx *ctx = req->ctx;
-	struct io_rsrc_node *node;
 	struct io_async_rw *io;
 	int ret;
 
@@ -351,13 +349,8 @@ static int io_prep_rw_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe
 	if (unlikely(ret))
 		return ret;
 
-	node = io_rsrc_node_lookup(&ctx->buf_table, req->buf_index);
-	if (!node)
-		return -EFAULT;
-	io_req_assign_buf_node(req, node);
-
 	io = req->async_data;
-	ret = io_import_fixed(ddir, &io->iter, node->buf, rw->addr, rw->len);
+	ret = io_import_reg_buf(req, &io->iter, rw->addr, rw->len, ddir, 0);
 	iov_iter_save_state(&io->iter, &io->iter_state);
 	return ret;
 }
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index 28ed69c40756..31d5e0948af1 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -199,21 +199,9 @@ int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	if (ioucmd->flags & ~IORING_URING_CMD_MASK)
 		return -EINVAL;
 
-	if (ioucmd->flags & IORING_URING_CMD_FIXED) {
-		struct io_ring_ctx *ctx = req->ctx;
-		struct io_rsrc_node *node;
-		u16 index = READ_ONCE(sqe->buf_index);
-
-		node = io_rsrc_node_lookup(&ctx->buf_table, index);
-		if (unlikely(!node))
-			return -EFAULT;
-		/*
-		 * Pi node upfront, prior to io_uring_cmd_import_fixed()
-		 * being called. This prevents destruction of the mapped buffer
-		 * we'll need at actual import time.
-		 */
-		io_req_assign_buf_node(req, node);
-	}
+	if (ioucmd->flags & IORING_URING_CMD_FIXED)
+		req->buf_index = READ_ONCE(sqe->buf_index);
+
 	ioucmd->cmd_op = READ_ONCE(sqe->cmd_op);
 
 	return io_uring_cmd_prep_setup(req, sqe);
@@ -261,13 +249,8 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      unsigned int issue_flags)
 {
 	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
-	struct io_rsrc_node *node = req->buf_node;
-
-	/* Must have had rsrc_node assigned at prep time */
-	if (node)
-		return io_import_fixed(rw, iter, node->buf, ubuf, len);
 
-	return -EFAULT;
+	return io_import_reg_buf(req, iter, ubuf, len, rw, issue_flags);
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);