io_uring/rw: add separate prep handler for readv/writev

Rather than sprinkle opcode checks in the generic read/write prep handler,
have a separate prep handler for the vectored readv/writev operation.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

io_uring/opdef.c

@@ -66,7 +66,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
 		.vectored		= 1,
-		.prep			= io_prep_rw,
+		.prep			= io_prep_rwv,
 		.issue			= io_read,
 	},
 	[IORING_OP_WRITEV] = {
@@ -80,7 +80,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
 		.vectored		= 1,
-		.prep			= io_prep_rw,
+		.prep			= io_prep_rwv,
 		.issue			= io_write,
 	},
 	[IORING_OP_FSYNC] = {

io_uring/rw.c

@@ -110,15 +110,23 @@ int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	rw->addr = READ_ONCE(sqe->addr);
 	rw->len = READ_ONCE(sqe->len);
 	rw->flags = READ_ONCE(sqe->rw_flags);
+	return 0;
+}
 
-	/* Have to do this validation here, as this is in io_read() rw->len might
-	 * have chanaged due to buffer selection
+int io_prep_rwv(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	int ret;
+
+	ret = io_prep_rw(req, sqe);
+	if (unlikely(ret))
+		return ret;
+
+	/*
+	 * Have to do this validation here, as this is in io_read() rw->len
+	 * might have chanaged due to buffer selection
 	 */
-	if (req->opcode == IORING_OP_READV && req->flags & REQ_F_BUFFER_SELECT) {
-		ret = io_iov_buffer_select_prep(req);
-		if (ret)
-			return ret;
-	}
+	if (req->flags & REQ_F_BUFFER_SELECT)
+		return io_iov_buffer_select_prep(req);
 
 	return 0;
 }

io_uring/rw.h

@@ -16,6 +16,7 @@ struct io_async_rw {
 };
 
 int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+int io_prep_rwv(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_read(struct io_kiocb *req, unsigned int issue_flags);
 int io_readv_prep_async(struct io_kiocb *req);
 int io_write(struct io_kiocb *req, unsigned int issue_flags);