3888 zfs recv -F should destroy any snapshots created since the incremental source
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Peng Dai <peng.dai@delphix.com>

@@ -1531,31 +1531,31 @@
         *usedobjsp = ds->ds_phys->ds_bp.blk_fill;
         *availobjsp = DN_MAX_OBJECT - *usedobjsp;
 }
 
 boolean_t
-dsl_dataset_modified_since_lastsnap(dsl_dataset_t *ds)
+dsl_dataset_modified_since_snap(dsl_dataset_t *ds, dsl_dataset_t *snap)
 {
         dsl_pool_t *dp = ds->ds_dir->dd_pool;
 
         ASSERT(dsl_pool_config_held(dp));
-        if (ds->ds_prev == NULL)
+        if (snap == NULL)
                 return (B_FALSE);
         if (ds->ds_phys->ds_bp.blk_birth >
-            ds->ds_prev->ds_phys->ds_creation_txg) {
-                objset_t *os, *os_prev;
+            snap->ds_phys->ds_creation_txg) {
+                objset_t *os, *os_snap;
                 /*
                  * It may be that only the ZIL differs, because it was
                  * reset in the head.  Don't count that as being
                  * modified.
                  */
                 if (dmu_objset_from_ds(ds, &os) != 0)
                         return (B_TRUE);
-                if (dmu_objset_from_ds(ds->ds_prev, &os_prev) != 0)
+                if (dmu_objset_from_ds(snap, &os_snap) != 0)
                         return (B_TRUE);
                 return (bcmp(&os->os_phys->os_meta_dnode,
-                    &os_prev->os_phys->os_meta_dnode,
+                    &os_snap->os_phys->os_meta_dnode,
                     sizeof (os->os_phys->os_meta_dnode)) != 0);
         }
         return (B_FALSE);
 }
 

@@ -2354,27 +2354,27 @@
         /* they should both be heads */
         if (dsl_dataset_is_snapshot(clone) ||
             dsl_dataset_is_snapshot(origin_head))
                 return (SET_ERROR(EINVAL));
 
-        /* the branch point should be just before them */
-        if (clone->ds_prev != origin_head->ds_prev)
+        /* if we are not forcing, the branch point should be just before them */
+        if (!force && clone->ds_prev != origin_head->ds_prev)
                 return (SET_ERROR(EINVAL));
 
         /* clone should be the clone (unless they are unrelated) */
         if (clone->ds_prev != NULL &&
             clone->ds_prev != clone->ds_dir->dd_pool->dp_origin_snap &&
-            origin_head->ds_object !=
-            clone->ds_prev->ds_phys->ds_next_snap_obj)
+            origin_head->ds_dir != clone->ds_prev->ds_dir)
                 return (SET_ERROR(EINVAL));
 
         /* the clone should be a child of the origin */
         if (clone->ds_dir->dd_parent != origin_head->ds_dir)
                 return (SET_ERROR(EINVAL));
 
         /* origin_head shouldn't be modified unless 'force' */
-        if (!force && dsl_dataset_modified_since_lastsnap(origin_head))
+        if (!force &&
+            dsl_dataset_modified_since_snap(origin_head, origin_head->ds_prev))
                 return (SET_ERROR(ETXTBSY));
 
         /* origin_head should have no long holds (e.g. is not mounted) */
         if (dsl_dataset_handoff_check(origin_head, owner, tx))
                 return (SET_ERROR(EBUSY));

@@ -2407,10 +2407,11 @@
         int64_t unused_refres_delta;
 
         ASSERT(clone->ds_reserved == 0);
         ASSERT(origin_head->ds_quota == 0 ||
             clone->ds_phys->ds_unique_bytes <= origin_head->ds_quota);
+        ASSERT3P(clone->ds_prev, ==, origin_head->ds_prev);
 
         dmu_buf_will_dirty(clone->ds_dbuf, tx);
         dmu_buf_will_dirty(origin_head->ds_dbuf, tx);
 
         if (clone->ds_objset != NULL) {