MDEV-22931 mtr_t::mtr_t() allocates some memory

mtr_t::m_freed_pages: Renamed from m_freed_ranges and made it as
pointer indirection.

mtr_t::add_freed_offset(): Allocates m_freed_pages.

mtr_t:clear_freed_ranges(): Removed.

mtr_t::init(): Added debug assertion to check whether m_freed_pages
is not yet initialized.

btr_page_alloc_low(): Remove #ifdef UNIV_DEBUG_SCRUBBING.

mtr_t::commit(): Delete m_freed_pages, reset m_trim_pages and
m_freed_in_system_tablespace.

fil_space_t::clear_freed_ranges(): Added a comment to explain how
undo log tablespaces uses it.

storage/innobase/btr/btr0btr.cc

@@ -537,22 +537,6 @@ btr_page_alloc_low(
 		seg_header, hint_page_no, file_direction,
 		true, mtr, init_mtr);
 
-#ifdef UNIV_DEBUG_SCRUBBING
-	if (block != NULL) {
-		fprintf(stderr,
-			"alloc %lu:%lu to index: %lu root: %lu\n",
-			buf_block_get_page_no(block),
-			buf_block_get_space(block),
-			index->id,
-			dict_index_get_page(index));
-	} else {
-		fprintf(stderr,
-			"failed alloc index: %lu root: %lu\n",
-			index->id,
-			dict_index_get_page(index));
-	}
-#endif /* UNIV_DEBUG_SCRUBBING */
-
 	return block;
 }
 

storage/innobase/include/fil0fil.h

@@ -502,7 +502,8 @@ struct fil_space_t
     last_freed_lsn= lsn;
   }
 
-  /** Clear all freed ranges */
+  /** Clear all freed ranges for undo tablespace when InnoDB
+  encounters TRIM redo log record */
   void clear_freed_ranges()
   {
     std::lock_guard<std::mutex> freed_lock(freed_range_mutex);

storage/innobase/include/mtr0log.h

@@ -511,6 +511,7 @@ inline void mtr_t::memcpy(const buf_block_t &b, void *dest, const void *str,
 @param[in,out]        b       buffer page */
 inline void mtr_t::init(buf_block_t *b)
 {
+  ut_ad(!m_freed_pages);
   b->page.status= buf_page_t::INIT_ON_FLUSH;
 
   if (m_log_mode != MTR_LOG_ALL)

storage/innobase/include/mtr0mtr.h

@@ -580,16 +580,11 @@ struct mtr_t {
   void add_freed_offset(page_id_t id)
   {
     ut_ad(m_user_space == NULL || id.space() == m_user_space->id);
-    m_freed_ranges.add_value(id.page_no());
+    if (!m_freed_pages)
+      m_freed_pages= new range_set();
+    m_freed_pages->add_value(id.page_no());
   }
 
-  /** Clear the freed pages */
-  void clear_freed_ranges()
-  {
-    m_freed_ranges.clear();
-    m_freed_in_system_tablespace= 0;
-    m_trim_pages= false;
-  }
 private:
   /** Log a write of a byte string to a page.
   @param block   buffer page
@@ -685,7 +680,7 @@ struct mtr_t {
   lsn_t m_commit_lsn;
 
   /** set of freed page ids */
-  range_set m_freed_ranges;
+  range_set *m_freed_pages= nullptr;
 };
 
 #include "mtr0mtr.ic"

storage/innobase/mtr/mtr0mtr.cc

@@ -354,12 +354,8 @@ struct mtr_write_log_t {
 /** Start a mini-transaction. */
 void mtr_t::start()
 {
-#ifdef HAVE_valgrind_or_MSAN
-  char m_freed_ranges_vbits[sizeof m_freed_ranges];
-#endif
-  MEM_GET_VBITS(&m_freed_ranges, m_freed_ranges_vbits, sizeof m_freed_ranges);
   UNIV_MEM_INVALID(this, sizeof *this);
-  MEM_SET_VBITS(&m_freed_ranges, m_freed_ranges_vbits, sizeof m_freed_ranges);
+  UNIV_MEM_VALID(&m_freed_pages, sizeof(m_freed_pages));
 
   ut_d(m_start= true);
   ut_d(m_commit= false);
@@ -378,6 +374,7 @@ void mtr_t::start()
   m_user_space= nullptr;
   m_commit_lsn= 0;
   m_freed_in_system_tablespace= m_trim_pages= false;
+  ut_ad(!m_freed_pages);
 }
 
 /** Release the resources */
@@ -387,7 +384,6 @@ inline void mtr_t::release_resources()
   ut_d(m_memo.for_each_block_in_reverse(CIterate<DebugCheck>()));
   m_log.erase();
   m_memo.erase();
-  clear_freed_ranges();
   ut_d(m_commit= true);
 }
 
@@ -420,8 +416,9 @@ void mtr_t::commit()
     to insert into the flush list. */
     log_mutex_exit();
 
-    if (!m_freed_ranges.empty())
+    if (m_freed_pages)
     {
+      ut_ad(!m_freed_pages->empty());
       fil_space_t *freed_space= m_user_space;
       /* Get the freed tablespace in case of predefined tablespace */
       if (!freed_space)
@@ -434,14 +431,15 @@ void mtr_t::commit()
       /* Update the last freed lsn */
       freed_space->update_last_freed_lsn(m_commit_lsn);
 
-      for (const auto &range : m_freed_ranges)
-        freed_space->add_free_range(range);
-    }
-
-    if (is_trim_pages())
-    {
-      ut_ad(m_user_space != nullptr);
-      m_user_space->clear_freed_ranges();
+      if (!is_trim_pages())
+        for (const auto &range : *m_freed_pages)
+          freed_space->add_free_range(range);
+      else
+        freed_space->clear_freed_ranges();
+      delete m_freed_pages;
+      m_freed_pages= nullptr;
+      /* Reset of m_trim_pages and m_freed_in_system_tablespace
+      happens in mtr_t::start() */
     }
 
     m_memo.for_each_block_in_reverse(CIterate<const ReleaseBlocks>
@@ -472,7 +470,7 @@ void mtr_t::commit_files(lsn_t checkpoint_lsn)
 	ut_ad(!m_made_dirty);
 	ut_ad(m_memo.size() == 0);
 	ut_ad(!srv_read_only_mode);
-	ut_ad(m_freed_ranges.empty());
+	ut_ad(!m_freed_pages);
 	ut_ad(!m_freed_in_system_tablespace);
 
 	if (checkpoint_lsn) {