rbd: replace obj_req->tried_parent with obj_req->read_state

Make rbd_obj_handle_read() look like a state machine and get rid of
the necessity to patch result in rbd_obj_handle_request(), completing
the removal of obj_req->xferred and img_req->xferred.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Dongsheng Yang <dongsheng.yang@easystack.cn>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index a9b0b23148f9263c45b2a1054b6d192ef90b6570..7925b2fdde79222e709997f3b973b62f78496807 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -219,6 +219,11 @@ enum obj_operation_type {
        OBJ_OP_ZEROOUT,
 };
 
+enum rbd_obj_read_state {
+       RBD_OBJ_READ_OBJECT = 1,
+       RBD_OBJ_READ_PARENT,
+};
+
 /*
  * Writes go through the following state machine to deal with
  * layering:
@@ -255,7 +260,7 @@ enum rbd_obj_write_state {
 struct rbd_obj_request {
        struct ceph_object_extent ex;
        union {
-               bool                    tried_parent;   /* for reads */
+               enum rbd_obj_read_state  read_state;    /* for reads */
                enum rbd_obj_write_state write_state;   /* for writes */
        };
 
@@ -1794,6 +1799,7 @@ static int rbd_obj_setup_read(struct rbd_obj_request *obj_req)
        rbd_osd_req_setup_data(obj_req, 0);
 
        rbd_osd_req_format_read(obj_req);
+       obj_req->read_state = RBD_OBJ_READ_OBJECT;
        return 0;
 }
 
@@ -2402,44 +2408,48 @@ static bool rbd_obj_handle_read(struct rbd_obj_request *obj_req, int *result)
        struct rbd_device *rbd_dev = obj_req->img_request->rbd_dev;
        int ret;
 
-       if (*result == -ENOENT &&
-           rbd_dev->parent_overlap && !obj_req->tried_parent) {
-               /* reverse map this object extent onto the parent */
-               ret = rbd_obj_calc_img_extents(obj_req, false);
-               if (ret) {
-                       *result = ret;
-                       return true;
-               }
-
-               if (obj_req->num_img_extents) {
-                       obj_req->tried_parent = true;
-                       ret = rbd_obj_read_from_parent(obj_req);
+       switch (obj_req->read_state) {
+       case RBD_OBJ_READ_OBJECT:
+               if (*result == -ENOENT && rbd_dev->parent_overlap) {
+                       /* reverse map this object extent onto the parent */
+                       ret = rbd_obj_calc_img_extents(obj_req, false);
                        if (ret) {
                                *result = ret;
                                return true;
                        }
-                       return false;
+                       if (obj_req->num_img_extents) {
+                               ret = rbd_obj_read_from_parent(obj_req);
+                               if (ret) {
+                                       *result = ret;
+                                       return true;
+                               }
+                               obj_req->read_state = RBD_OBJ_READ_PARENT;
+                               return false;
+                       }
                }
-       }
 
-       /*
-        * -ENOENT means a hole in the image -- zero-fill the entire
-        * length of the request.  A short read also implies zero-fill
-        * to the end of the request.
-        */
-       if (*result == -ENOENT) {
-               rbd_obj_zero_range(obj_req, 0, obj_req->ex.oe_len);
-               *result = 0;
-       } else if (*result >= 0) {
-               if (*result < obj_req->ex.oe_len)
-                       rbd_obj_zero_range(obj_req, *result,
-                                          obj_req->ex.oe_len - *result);
-               else
-                       rbd_assert(*result == obj_req->ex.oe_len);
-               *result = 0;
+               /*
+                * -ENOENT means a hole in the image -- zero-fill the entire
+                * length of the request.  A short read also implies zero-fill
+                * to the end of the request.
+                */
+               if (*result == -ENOENT) {
+                       rbd_obj_zero_range(obj_req, 0, obj_req->ex.oe_len);
+                       *result = 0;
+               } else if (*result >= 0) {
+                       if (*result < obj_req->ex.oe_len)
+                               rbd_obj_zero_range(obj_req, *result,
+                                               obj_req->ex.oe_len - *result);
+                       else
+                               rbd_assert(*result == obj_req->ex.oe_len);
+                       *result = 0;
+               }
+               return true;
+       case RBD_OBJ_READ_PARENT:
+               return true;
+       default:
+               BUG();
        }
-
-       return true;
 }
 
 /*
@@ -2658,11 +2668,11 @@ static bool rbd_obj_handle_write(struct rbd_obj_request *obj_req, int *result)
        case RBD_OBJ_WRITE_COPYUP_OPS:
                return true;
        case RBD_OBJ_WRITE_READ_FROM_PARENT:
-               if (*result < 0)
+               if (*result)
                        return true;
 
-               rbd_assert(*result);
-               ret = rbd_obj_issue_copyup(obj_req, *result);
+               ret = rbd_obj_issue_copyup(obj_req,
+                                          rbd_obj_img_extents_bytes(obj_req));
                if (ret) {
                        *result = ret;
                        return true;
@@ -2757,7 +2767,7 @@ again:
        rbd_assert(img_req->result <= 0);
        if (test_bit(IMG_REQ_CHILD, &img_req->flags)) {
                obj_req = img_req->obj_request;
-               result = img_req->result ?: rbd_obj_img_extents_bytes(obj_req);
+               result = img_req->result;
                rbd_img_request_put(img_req);
                goto again;
        }