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>

1 files changed, 46 insertions, 36 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index a9b0b23148f9..7925b2fdde79 100644
--- 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;
         }