io_uring/rw: add separate prep handler for fixed read/write

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

@@ -98,7 +98,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.ioprio			= 1,
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
-		.prep			= io_prep_rw,
+		.prep			= io_prep_rw_fixed,
 		.issue			= io_read,
 	},
 	[IORING_OP_WRITE_FIXED] = {
@@ -111,7 +111,7 @@ const struct io_issue_def io_issue_defs[] = {
 		.ioprio			= 1,
 		.iopoll			= 1,
 		.iopoll_queue		= 1,
-		.prep			= io_prep_rw,
+		.prep			= io_prep_rw_fixed,
 		.issue			= io_write,
 	},
 	[IORING_OP_POLL_ADD] = {

io_uring/rw.c

@@ -83,18 +83,6 @@ int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	/* used for fixed read/write too - just read unconditionally */
 	req->buf_index = READ_ONCE(sqe->buf_index);
 
-	if (req->opcode == IORING_OP_READ_FIXED ||
-	    req->opcode == IORING_OP_WRITE_FIXED) {
-		struct io_ring_ctx *ctx = req->ctx;
-		u16 index;
-
-		if (unlikely(req->buf_index >= ctx->nr_user_bufs))
-			return -EFAULT;
-		index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
-		req->imu = ctx->user_bufs[index];
-		io_req_set_rsrc_node(req, ctx, 0);
-	}
-
 	ioprio = READ_ONCE(sqe->ioprio);
 	if (ioprio) {
 		ret = ioprio_check_cap(ioprio);
@@ -131,6 +119,24 @@ int io_prep_rwv(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	return 0;
 }
 
+int io_prep_rw_fixed(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	u16 index;
+	int ret;
+
+	ret = io_prep_rw(req, sqe);
+	if (unlikely(ret))
+		return ret;
+
+	if (unlikely(req->buf_index >= ctx->nr_user_bufs))
+		return -EFAULT;
+	index = array_index_nospec(req->buf_index, ctx->nr_user_bufs);
+	req->imu = ctx->user_bufs[index];
+	io_req_set_rsrc_node(req, ctx, 0);
+	return 0;
+}
+
 /*
  * Multishot read is prepared just like a normal read/write request, only
  * difference is that we set the MULTISHOT flag.

io_uring/rw.h

@@ -17,6 +17,7 @@ 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_prep_rw_fixed(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);