io_uring/cmd: introduce io_uring_cmd_import_fixed_vec

io_uring_cmd_import_fixed_vec() is a cmd helper around vectored
registered buffer import functions, which caches the memory under
the hood. The lifetime of the vectore and hence the iterator is bound to
the request. Furthermore, the user is not allowed to call it multiple
times for a single request.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/97487a80dec3fb8cf8aeedf1f9026ef6d503fe4b.1742579999.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/io_uring/cmd.h

@@ -43,6 +43,11 @@ 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_vec(struct io_uring_cmd *ioucmd,
+				  const struct iovec __user *uvec,
+				  size_t uvec_segs,
+				  int ddir, struct iov_iter *iter,
+				  unsigned issue_flags);
 
 /*
  * Completes the request, i.e. posts an io_uring CQE and deallocates @ioucmd
@@ -76,6 +81,14 @@ io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
 {
 	return -EOPNOTSUPP;
 }
+static inline int io_uring_cmd_import_fixed_vec(struct io_uring_cmd *ioucmd,
+						const struct iovec __user *uvec,
+						size_t uvec_segs,
+						int ddir, struct iov_iter *iter,
+						unsigned issue_flags)
+{
+	return -EOPNOTSUPP;
+}
 static inline void io_uring_cmd_done(struct io_uring_cmd *cmd, ssize_t ret,
 		u64 ret2, unsigned issue_flags)
 {

io_uring/uring_cmd.c

@@ -277,6 +277,25 @@ 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_vec(struct io_uring_cmd *ioucmd,
+				  const struct iovec __user *uvec,
+				  size_t uvec_segs,
+				  int ddir, struct iov_iter *iter,
+				  unsigned issue_flags)
+{
+	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
+	struct io_async_cmd *ac = req->async_data;
+	int ret;
+
+	ret = io_prep_reg_iovec(req, &ac->vec, uvec, uvec_segs);
+	if (ret)
+		return ret;
+
+	return io_import_reg_vec(ddir, iter, req, &ac->vec, uvec_segs,
+				 issue_flags);
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed_vec);
+
 void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd)
 {
 	struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);

io_uring/uring_cmd.h

@@ -16,3 +16,9 @@ bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
 				   struct io_uring_task *tctx, bool cancel_all);
 
 void io_cmd_cache_free(const void *entry);
+
+int io_uring_cmd_import_fixed_vec(struct io_uring_cmd *ioucmd,
+				  const struct iovec __user *uvec,
+				  size_t uvec_segs,
+				  int ddir, struct iov_iter *iter,
+				  unsigned issue_flags);