MDEV-25506 (2 of 3): Kill during DDL leaves orphan .ibd file

dict_drop_index_tree(): Even if SYS_INDEXES.PAGE contains the
special value FIL_NULL, the tablespace identified by SYS_INDEXES.SPACE
may exist and may need to be dropped. This would definitely be the case
if the server had been killed right after a FILE_CREATE record was
persistently written during CREATE TABLE, but before the transaction
was committed.

btr_free_if_exists(): Simplify the interface, to avoid repeated
tablespace lookup.

One more scenario is known to be broken: If the server is killed
during DROP TABLE (or table-rebuilding ALTER TABLE) right after a
FILE_DELETE record has been persistently written but before the
file was deleted, then we could end up recovering no tablespace
at all, and failing to delete the file, in either of fil_name_process()
or dict_drop_index_tree().

Thanks to Elena Stepanova for providing "rr replay" and data directories
of these scenarios.

storage/innobase/btr/btr0btr.cc

@@ -1225,23 +1225,20 @@ void dict_index_t::clear(que_thr_t *thr)
 }
 
 /** Free a persistent index tree if it exists.
-@param[in]	page_id		root page id
-@param[in]	zip_size	ROW_FORMAT=COMPRESSED page size, or 0
+@param[in,out]	space		tablespce
+@param[in]	page		root page number
 @param[in]	index_id	PAGE_INDEX_ID contents
 @param[in,out]	mtr		mini-transaction */
-void btr_free_if_exists(const page_id_t page_id, ulint zip_size,
+void btr_free_if_exists(fil_space_t *space, uint32_t page,
                         index_id_t index_id, mtr_t *mtr)
 {
-  if (fil_space_t *space= fil_space_t::get(page_id.space()))
+  if (buf_block_t *root= btr_free_root_check(page_id_t(space->id, page),
+					     space->zip_size(),
+					     index_id, mtr))
   {
-    if (buf_block_t *root= btr_free_root_check(page_id, zip_size, index_id,
-                                               mtr))
-    {
-      btr_free_but_not_root(root, mtr->get_log_mode());
-      mtr->set_named_space(space);
-      btr_free_root(root, mtr);
-    }
-    space->release();
+    btr_free_but_not_root(root, mtr->get_log_mode());
+    mtr->set_named_space(space);
+    btr_free_root(root, mtr);
   }
 }
 

storage/innobase/dict/dict0crea.cc

@@ -871,17 +871,8 @@ void dict_drop_index_tree(btr_pcur_t *pcur, trx_t *trx, dict_table_t *table,
   if (len != 4)
     goto rec_corrupted;
 
-  if (root_page_no == FIL_NULL)
-    /* The tree has already been freed */
-    return;
-
-  static_assert(FIL_NULL == 0xffffffff, "compatibility");
-  static_assert(DICT_FLD__SYS_INDEXES__PAGE_NO ==
-                DICT_FLD__SYS_INDEXES__SPACE + 1, "compatibility");
-  mtr->memset(btr_pcur_get_block(pcur), page_offset(p + 4), 4, 0xff);
-
   const uint32_t space_id= mach_read_from_4(p);
-  ut_ad(space_id < SRV_TMP_SPACE_ID);
+  ut_ad(root_page_no == FIL_NULL || space_id <= SRV_SPACE_ID_UPPER_BOUND);
 
   if (space_id && (type & DICT_CLUSTERED))
   {
@@ -891,13 +882,20 @@ void dict_drop_index_tree(btr_pcur_t *pcur, trx_t *trx, dict_table_t *table,
       ut_ad(!table);
     fil_delete_tablespace(space_id, true);
   }
+  else if (root_page_no == FIL_NULL)
+    /* The tree has already been freed */;
   else if (fil_space_t*s= fil_space_t::get(space_id))
   {
     /* Ensure that the tablespace file exists
     in order to avoid a crash in buf_page_get_gen(). */
     if (root_page_no < s->get_size())
-      btr_free_if_exists(page_id_t(space_id, root_page_no), s->zip_size(),
-                         mach_read_from_8(rec + 8), mtr);
+    {
+      static_assert(FIL_NULL == 0xffffffff, "compatibility");
+      static_assert(DICT_FLD__SYS_INDEXES__PAGE_NO ==
+                    DICT_FLD__SYS_INDEXES__SPACE + 1, "compatibility");
+      mtr->memset(btr_pcur_get_block(pcur), page_offset(p + 4), 4, 0xff);
+      btr_free_if_exists(s, root_page_no, mach_read_from_8(rec + 8), mtr);
+    }
     s->release();
   }
 }

storage/innobase/include/btr0btr.h

@@ -2,7 +2,7 @@
 
 Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
-Copyright (c) 2014, 2020, MariaDB Corporation.
+Copyright (c) 2014, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -330,16 +330,12 @@ btr_create(
 	mtr_t*			mtr);
 
 /** Free a persistent index tree if it exists.
-@param[in]	page_id		root page id
-@param[in]	zip_size	ROW_FORMAT=COMPRESSED page size, or 0
+@param[in,out]	space		tablespce
+@param[in]	page		root page number
 @param[in]	index_id	PAGE_INDEX_ID contents
 @param[in,out]	mtr		mini-transaction */
-void
-btr_free_if_exists(
-	const page_id_t		page_id,
-	ulint			zip_size,
-	index_id_t		index_id,
-	mtr_t*			mtr);
+void btr_free_if_exists(fil_space_t *space, uint32_t page,
+                        index_id_t index_id, mtr_t *mtr);
 
 /** Free an index tree in a temporary tablespace.
 @param[in]	page_id		root page id */