RDMA/uverbs: Get rid of the 'callback' scheme in the compat path

There is no reason for this. For response processing we simply need to
copy, truncate, and zero fill the response into whatever output buffer
was provided. Add a function uverbs_response() that does this
consistently.
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/core/uverbs_cmd.c

@@ -47,6 +47,35 @@
 #include "uverbs.h"
 #include "core_priv.h"
 
+/*
+ * Copy a response to userspace. If the provided 'resp' is larger than the
+ * user buffer it is silently truncated. If the user provided a larger buffer
+ * then the trailing portion is zero filled.
+ *
+ * These semantics are intended to support future extension of the output
+ * structures.
+ */
+static int uverbs_response(struct uverbs_attr_bundle *attrs, const void *resp,
+			   size_t resp_len)
+{
+	u8 __user *cur = attrs->ucore.outbuf + resp_len;
+	u8 __user *end = attrs->ucore.outbuf + attrs->ucore.outlen;
+	int ret;
+
+	if (copy_to_user(attrs->ucore.outbuf, resp,
+			 min(attrs->ucore.outlen, resp_len)))
+		return -EFAULT;
+
+	/* Zero fill any extra memory that user space might have provided */
+	for (; cur < end; cur++) {
+		ret = put_user(0, cur);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
 static struct ib_uverbs_completion_event_file *
 _ib_uverbs_lookup_comp_file(s32 fd, const struct uverbs_attr_bundle *attrs)
 {
@@ -892,12 +921,7 @@ static int ib_uverbs_create_comp_channel(struct uverbs_attr_bundle *attrs,
 
 static struct ib_ucq_object *create_cq(struct uverbs_attr_bundle *attrs,
 				       struct ib_uverbs_ex_create_cq *cmd,
-				       size_t cmd_sz,
-				       int (*cb)(struct uverbs_attr_bundle *attrs,
-						 struct ib_ucq_object *obj,
-						 struct ib_uverbs_ex_create_cq_resp *resp,
-						 void *context),
-				       void *context)
+				       size_t cmd_sz)
 {
 	struct ib_ucq_object           *obj;
 	struct ib_uverbs_completion_event_file    *ev_file = NULL;
@@ -953,14 +977,12 @@ static struct ib_ucq_object *create_cq(struct uverbs_attr_bundle *attrs,
 	memset(&resp, 0, sizeof resp);
 	resp.base.cq_handle = obj->uobject.id;
 	resp.base.cqe       = cq->cqe;
-
-	resp.response_length = offsetof(typeof(resp), response_length) +
-		sizeof(resp.response_length);
+	resp.response_length = sizeof(resp);
 
 	cq->res.type = RDMA_RESTRACK_CQ;
 	rdma_restrack_add(&cq->res);
 
-	ret = cb(attrs, obj, &resp, context);
+	ret = uverbs_response(attrs, &resp, sizeof(resp));
 	if (ret)
 		goto err_cb;
 
@@ -982,17 +1004,6 @@ static struct ib_ucq_object *create_cq(struct uverbs_attr_bundle *attrs,
 	return ERR_PTR(ret);
 }
 
-static int ib_uverbs_create_cq_cb(struct uverbs_attr_bundle *attrs,
-				  struct ib_ucq_object *obj,
-				  struct ib_uverbs_ex_create_cq_resp *resp,
-				  void *context)
-{
-	if (ib_copy_to_udata(&attrs->ucore, &resp->base, sizeof(resp->base)))
-		return -EFAULT;
-
-	return 0;
-}
-
 static int ib_uverbs_create_cq(struct uverbs_attr_bundle *attrs,
 			       const char __user *buf, int in_len, int out_len)
 {
@@ -1011,22 +1022,10 @@ static int ib_uverbs_create_cq(struct uverbs_attr_bundle *attrs,
 
 	obj = create_cq(attrs, &cmd_ex,
 			offsetof(typeof(cmd_ex), comp_channel) +
-				sizeof(cmd.comp_channel),
-			ib_uverbs_create_cq_cb, NULL);
+				sizeof(cmd.comp_channel));
 	return PTR_ERR_OR_ZERO(obj);
 }
 
-static int ib_uverbs_ex_create_cq_cb(struct uverbs_attr_bundle *attrs,
-				     struct ib_ucq_object *obj,
-				     struct ib_uverbs_ex_create_cq_resp *resp,
-				     void *context)
-{
-	if (ib_copy_to_udata(&attrs->ucore, resp, resp->response_length))
-		return -EFAULT;
-
-	return 0;
-}
-
 static int ib_uverbs_ex_create_cq(struct uverbs_attr_bundle *attrs,
 				  struct ib_udata *ucore)
 {
@@ -1052,9 +1051,7 @@ static int ib_uverbs_ex_create_cq(struct uverbs_attr_bundle *attrs,
 			     sizeof(resp.response_length)))
 		return -ENOSPC;
 
-	obj = create_cq(attrs, &cmd, min(ucore->inlen, sizeof(cmd)),
-			ib_uverbs_ex_create_cq_cb, NULL);
-
+	obj = create_cq(attrs, &cmd, min(ucore->inlen, sizeof(cmd)));
 	return PTR_ERR_OR_ZERO(obj);
 }
 
@@ -1219,10 +1216,7 @@ static int ib_uverbs_destroy_cq(struct uverbs_attr_bundle *attrs,
 }
 
 static int create_qp(struct uverbs_attr_bundle *attrs,
-		     struct ib_uverbs_ex_create_qp *cmd, size_t cmd_sz,
-		     int (*cb)(struct uverbs_attr_bundle *attrs,
-			       struct ib_uverbs_ex_create_qp_resp *resp),
-		     void *context)
+		     struct ib_uverbs_ex_create_qp *cmd, size_t cmd_sz)
 {
 	struct ib_uqp_object		*obj;
 	struct ib_device		*device;
@@ -1442,11 +1436,9 @@ static int create_qp(struct uverbs_attr_bundle *attrs,
 	resp.base.max_recv_wr     = attr.cap.max_recv_wr;
 	resp.base.max_send_wr     = attr.cap.max_send_wr;
 	resp.base.max_inline_data = attr.cap.max_inline_data;
+	resp.response_length = sizeof(resp);
 
-	resp.response_length = offsetof(typeof(resp), response_length) +
-			       sizeof(resp.response_length);
-
-	ret = cb(attrs, &resp);
+	ret = uverbs_response(attrs, &resp, sizeof(resp));
 	if (ret)
 		goto err_cb;
 
@@ -1490,21 +1482,11 @@ static int create_qp(struct uverbs_attr_bundle *attrs,
 	return ret;
 }
 
-static int ib_uverbs_create_qp_cb(struct uverbs_attr_bundle *attrs,
-				  struct ib_uverbs_ex_create_qp_resp *resp)
-{
-	if (ib_copy_to_udata(&attrs->ucore, &resp->base, sizeof(resp->base)))
-		return -EFAULT;
-
-	return 0;
-}
-
 static int ib_uverbs_create_qp(struct uverbs_attr_bundle *attrs,
 			       const char __user *buf, int in_len, int out_len)
 {
 	struct ib_uverbs_create_qp      cmd;
 	struct ib_uverbs_ex_create_qp	cmd_ex;
-	int				err;
 
 	if (copy_from_user(&cmd, buf, sizeof(cmd)))
 		return -EFAULT;
@@ -1524,23 +1506,8 @@ static int ib_uverbs_create_qp(struct uverbs_attr_bundle *attrs,
 	cmd_ex.qp_type = cmd.qp_type;
 	cmd_ex.is_srq = cmd.is_srq;
 
-	err = create_qp(attrs, &cmd_ex,
-			offsetof(typeof(cmd_ex), is_srq) + sizeof(cmd.is_srq),
-			ib_uverbs_create_qp_cb, NULL);
-
-	if (err)
-		return err;
-
-	return 0;
-}
-
-static int ib_uverbs_ex_create_qp_cb(struct uverbs_attr_bundle *attrs,
-				     struct ib_uverbs_ex_create_qp_resp *resp)
-{
-	if (ib_copy_to_udata(&attrs->ucore, resp, resp->response_length))
-		return -EFAULT;
-
-	return 0;
+	return create_qp(attrs, &cmd_ex,
+			 offsetof(typeof(cmd_ex), is_srq) + sizeof(cmd.is_srq));
 }
 
 static int ib_uverbs_ex_create_qp(struct uverbs_attr_bundle *attrs,
@@ -1568,14 +1535,7 @@ static int ib_uverbs_ex_create_qp(struct uverbs_attr_bundle *attrs,
 			     sizeof(resp.response_length)))
 		return -ENOSPC;
 
-	err = create_qp(attrs, &cmd,
-			min(ucore->inlen, sizeof(cmd)),
-			ib_uverbs_ex_create_qp_cb, NULL);
-
-	if (err)
-		return err;
-
-	return 0;
+	return create_qp(attrs, &cmd, min(ucore->inlen, sizeof(cmd)));
 }
 
 static int ib_uverbs_open_qp(struct uverbs_attr_bundle *attrs,