3752 want more verifiable dbuf user eviction
Submitted by:   Justin Gibbs <justing@spectralogic.com>
Submitted by:   Will Andrews <willa@spectralogic.com>

@@ -519,11 +519,11 @@
 zap_leaf(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
 {
         char buf[16*1024];
         int verbose = B_FALSE;
         int four = B_FALSE;
-        zap_leaf_t l;
+        zap_leaf_t l = { 0 };
         zap_leaf_phys_t *zlp = (void *)buf;
         int i;
 
         if (mdb_getopts(argc, argv,
             'v', MDB_OPT_SETBITS, TRUE, &verbose,

@@ -1423,12 +1423,21 @@
 typedef struct mdb_spa {
         uintptr_t spa_dsl_pool;
         uintptr_t spa_root_vdev;
 } mdb_spa_t;
 
+struct mdb_dsl_dir_phys;
+typedef struct mdb_dsl_dir_dbuf {
+        uint8_t dddb_pad[offsetof(dmu_buf_t, db_data)];
+        uintptr_t dddb_data;
+} mdb_dsl_dir_dbuf_t;
+
 typedef struct mdb_dsl_dir {
-        uintptr_t dd_phys;
+        union {
+                dmu_buf_t *dd_dmu_db;
+                mdb_dsl_dir_dbuf_t *dd_db;
+        } dd_db_u;
         int64_t dd_space_towrite[TXG_SIZE];
 } mdb_dsl_dir_t;
 
 typedef struct mdb_dsl_dir_phys {
         uint64_t dd_used_bytes;