Add an API for fetching the registered buffer associated with a
io_uring cmd. This is useful for callers who need access to the buffer
but do not have prior knowledge of the buffer's user address or length.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
---
 include/linux/io_uring/cmd.h |  3 +++
 io_uring/rsrc.c              | 14 ++++++++++++++
 io_uring/rsrc.h              |  2 ++
 io_uring/uring_cmd.c         | 13 +++++++++++++
 4 files changed, 32 insertions(+)

diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
index 7509025b4071..8c11d9a92733 100644
--- a/include/linux/io_uring/cmd.h
+++ b/include/linux/io_uring/cmd.h
@@ -43,6 +43,9 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 			      struct iov_iter *iter,
 			      struct io_uring_cmd *ioucmd,
 			      unsigned int issue_flags);
+int io_uring_cmd_import_fixed_full(int rw, struct iov_iter *iter,
+				   struct io_uring_cmd *ioucmd,
+				   unsigned int issue_flags);
 int io_uring_cmd_import_fixed_vec(struct io_uring_cmd *ioucmd,
 				  const struct iovec __user *uvec,
 				  size_t uvec_segs,
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index d787c16dc1c3..2c3d8489ae52 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1147,6 +1147,20 @@ int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,
 	return io_import_fixed(ddir, iter, node->buf, buf_addr, len);
 }
 
+int io_import_reg_buf_full(struct io_kiocb *req, struct iov_iter *iter,
+			   int ddir, unsigned issue_flags)
+{
+	struct io_rsrc_node *node;
+	struct io_mapped_ubuf *imu;
+
+	node = io_find_buf_node(req, issue_flags);
+	if (!node)
+		return -EFAULT;
+
+	imu = node->buf;
+	return io_import_fixed(ddir, iter, imu, imu->ubuf, imu->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 a3ca6ba66596..4e01eb0f277e 100644
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -64,6 +64,8 @@ struct io_rsrc_node *io_find_buf_node(struct io_kiocb *req,
 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_import_reg_buf_full(struct io_kiocb *req, struct iov_iter *iter,
+			   int ddir, unsigned issue_flags);
 int io_import_reg_vec(int ddir, struct iov_iter *iter,
 			struct io_kiocb *req, struct iou_vec *vec,
 			unsigned nr_iovs, unsigned issue_flags);
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index d1e3ba62ee8e..07730ced9449 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -292,6 +292,19 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 }
 EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);
 
+int io_uring_cmd_import_fixed_full(int rw, struct iov_iter *iter,
+				   struct io_uring_cmd *ioucmd,
+				   unsigned int issue_flags)
+{
+	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
+
+	if (WARN_ON_ONCE(!(ioucmd->flags & IORING_URING_CMD_FIXED)))
+		return -EINVAL;
+
+	return io_import_reg_buf_full(req, iter, rw, issue_flags);
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed_full);
+
 int io_uring_cmd_import_fixed_vec(struct io_uring_cmd *ioucmd,
 				  const struct iovec __user *uvec,
 				  size_t uvec_segs,
-- 
2.47.3