rbd: define parent image request routines

Define rbd_parent_request_create() and rbd_parent_request_destroy()
to handle the creation of parent image requests submitted for
layered image objects.  For simplicity, let rbd_img_request_put()
handle dropping the reference to any image request (parent or not),
and call whichever destructor is appropriate on the last put.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

1 files changed, 55 insertions, 23 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 9c2b20a88be2..1ffdfbfbf3c4 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1359,13 +1359,18 @@ static void rbd_obj_request_put(struct rbd_obj_request *obj_request)
         kref_put(&obj_request->kref, rbd_obj_request_destroy);
 }
 
+static bool img_request_child_test(struct rbd_img_request *img_request);
+static void rbd_parent_request_destroy(struct kref *kref);
 static void rbd_img_request_destroy(struct kref *kref);
 static void rbd_img_request_put(struct rbd_img_request *img_request)
 {
         rbd_assert(img_request != NULL);
         dout("%s: img %p (was %d)\n", __func__, img_request,
                 atomic_read(&img_request->kref.refcount));
-        kref_put(&img_request->kref, rbd_img_request_destroy);
+        if (img_request_child_test(img_request))
+                kref_put(&img_request->kref, rbd_parent_request_destroy);
+        else
+                kref_put(&img_request->kref, rbd_img_request_destroy);
 }
 
 static inline void rbd_img_obj_request_add(struct rbd_img_request *img_request,
@@ -1482,6 +1487,12 @@ static void img_request_child_set(struct rbd_img_request *img_request)
         smp_mb();
 }
 
+static void img_request_child_clear(struct rbd_img_request *img_request)
+{
+        clear_bit(IMG_REQ_CHILD, &img_request->flags);
+        smp_mb();
+}
+
 static bool img_request_child_test(struct rbd_img_request *img_request)
 {
         smp_mb();
@@ -1856,8 +1867,7 @@ static void rbd_dev_unparent(struct rbd_device *rbd_dev)
 static struct rbd_img_request *rbd_img_request_create(
                                         struct rbd_device *rbd_dev,
                                         u64 offset, u64 length,
-                                        bool write_request,
-                                        bool child_request)
+                                        bool write_request)
 {
         struct rbd_img_request *img_request;
 
@@ -1882,8 +1892,6 @@ static struct rbd_img_request *rbd_img_request_create(
         } else {
                 img_request->snap_id = rbd_dev->spec->snap_id;
         }
-        if (child_request)
-                img_request_child_set(img_request);
         if (rbd_dev->parent_overlap)
                 img_request_layered_set(img_request);
         spin_lock_init(&img_request->completion_lock);
@@ -1918,12 +1926,46 @@ static void rbd_img_request_destroy(struct kref *kref)
         if (img_request_write_test(img_request))
                 ceph_put_snap_context(img_request->snapc);
 
-        if (img_request_child_test(img_request))
-                rbd_obj_request_put(img_request->obj_request);
-
         kmem_cache_free(rbd_img_request_cache, img_request);
 }
 
+static struct rbd_img_request *rbd_parent_request_create(
+                                        struct rbd_obj_request *obj_request,
+                                        u64 img_offset, u64 length)
+{
+        struct rbd_img_request *parent_request;
+        struct rbd_device *rbd_dev;
+
+        rbd_assert(obj_request->img_request);
+        rbd_dev = obj_request->img_request->rbd_dev;
+
+        parent_request = rbd_img_request_create(rbd_dev->parent,
+                                                img_offset, length, false);
+        if (!parent_request)
+                return NULL;
+
+        img_request_child_set(parent_request);
+        rbd_obj_request_get(obj_request);
+        parent_request->obj_request = obj_request;
+
+        return parent_request;
+}
+
+static void rbd_parent_request_destroy(struct kref *kref)
+{
+        struct rbd_img_request *parent_request;
+        struct rbd_obj_request *orig_request;
+
+        parent_request = container_of(kref, struct rbd_img_request, kref);
+        orig_request = parent_request->obj_request;
+
+        parent_request->obj_request = NULL;
+        rbd_obj_request_put(orig_request);
+        img_request_child_clear(parent_request);
+
+        rbd_img_request_destroy(kref);
+}
+
 static bool rbd_img_obj_end_request(struct rbd_obj_request *obj_request)
 {
         struct rbd_img_request *img_request;
@@ -2321,13 +2363,10 @@ static int rbd_img_obj_parent_read_full(struct rbd_obj_request *obj_request)
         }
 
         result = -ENOMEM;
-        parent_request = rbd_img_request_create(rbd_dev->parent,
-                                                img_offset, length,
-                                                false, true);
+        parent_request = rbd_parent_request_create(obj_request,
+                                                img_offset, length);
         if (!parent_request)
                 goto out_err;
-        rbd_obj_request_get(obj_request);
-        parent_request->obj_request = obj_request;
 
         result = rbd_img_request_fill(parent_request, OBJ_REQUEST_PAGES, pages);
         if (result)
@@ -2580,7 +2619,6 @@ out:
 
 static void rbd_img_parent_read(struct rbd_obj_request *obj_request)
 {
-        struct rbd_device *rbd_dev;
         struct rbd_img_request *img_request;
         int result;
 
@@ -2589,20 +2627,14 @@ static void rbd_img_parent_read(struct rbd_obj_request *obj_request)
         rbd_assert(obj_request->result == (s32) -ENOENT);
         rbd_assert(obj_request_type_valid(obj_request->type));
 
-        rbd_dev = obj_request->img_request->rbd_dev;
-        rbd_assert(rbd_dev->parent != NULL);
         /* rbd_read_finish(obj_request, obj_request->length); */
-        img_request = rbd_img_request_create(rbd_dev->parent,
+        img_request = rbd_parent_request_create(obj_request,
                                                 obj_request->img_offset,
-                                                obj_request->length,
-                                                false, true);
+                                                obj_request->length);
         result = -ENOMEM;
         if (!img_request)
                 goto out_err;
 
-        rbd_obj_request_get(obj_request);
-        img_request->obj_request = obj_request;
-
         if (obj_request->type == OBJ_REQUEST_BIO)
                 result = rbd_img_request_fill(img_request, OBJ_REQUEST_BIO,
                                                 obj_request->bio_list);
@@ -2913,7 +2945,7 @@ static void rbd_request_fn(struct request_queue *q)
 
                 result = -ENOMEM;
                 img_request = rbd_img_request_create(rbd_dev, offset, length,
-                                                        write_request, false);
+                                                        write_request);
                 if (!img_request)
                         goto end_request;