MDEV-32042 Simplify buf_page_get_gen()

buf_page_get_low(): Rename to buf_page_get_gen(), and assume that no
crash recovery is needed.

recv_sys_t::recover(): Replaces the old buf_page_get_gen(). Read a page
while crash recovery is in progress.

trx_rseg_get_n_undo_tablespaces(), ibuf_upgrade_needed():
Invoke recv_sys.recover() instead of buf_page_get_gen().

dict_boot(): Invoke recv_sys.recover() instead of buf_page_get_gen().
Do not load the system tables.

srv_start(): Load the system tables and the undo logs after all redo log
has been applied in recv_sys.apply(true) and we can safely invoke the
regular buf_page_get_gen().

storage/innobase/btr/btr0btr.cc

@@ -1114,9 +1114,9 @@ void btr_drop_temporary_table(const dict_table_t &table)
   for (const dict_index_t *index= table.indexes.start; index;
        index= dict_table_get_next_index(index))
   {
-    if (buf_block_t *block= buf_page_get_low({SRV_TMP_SPACE_ID, index->page}, 0,
-                                             RW_X_LATCH, nullptr, BUF_GET, &mtr,
-                                             nullptr))
+    if (buf_block_t *block= buf_page_get_gen({SRV_TMP_SPACE_ID, index->page},
+                                             0, RW_X_LATCH, nullptr, BUF_GET,
+                                             &mtr, nullptr))
     {
       btr_free_but_not_root(block, MTR_LOG_NO_REDO);
       mtr.set_log_mode(MTR_LOG_NO_REDO);

storage/innobase/buf/buf0buf.cc

@@ -2585,7 +2585,7 @@ or BUF_PEEK_IF_IN_POOL
 @return pointer to the block or NULL */
 TRANSACTIONAL_TARGET
 buf_block_t*
-buf_page_get_low(
+buf_page_get_gen(
 	const page_id_t		page_id,
 	ulint			zip_size,
 	ulint			rw_latch,
@@ -2778,7 +2778,7 @@ buf_page_get_low(
 wait_for_unzip:
 			/* The page is being read or written, or
 			another thread is executing buf_zip_decompress()
-			in buf_page_get_low() on it. */
+			in buf_page_get_gen() on it. */
 			block->page.unfix();
 			std::this_thread::sleep_for(
 				std::chrono::microseconds(100));
@@ -2801,10 +2801,7 @@ buf_page_get_low(
 		ut_ad(&block->page == buf_pool.page_hash.get(page_id, chain));
 
 		/* Wait for any other threads to release their buffer-fix
-		on the compressed-only block descriptor.
-		FIXME: Never fix() before acquiring the lock.
-		Only in buf_page_get_gen(), buf_page_get_low(), buf_page_free()
-		we are violating that principle. */
+		on the compressed-only block descriptor. */
 		state = block->page.state();
 
 		switch (state) {
@@ -2830,7 +2827,7 @@ buf_page_get_low(
 			goto wait_for_unfix;
 		}
 
-		/* Ensure that another buf_page_get_low() will wait for
+		/* Ensure that another buf_page_get_gen() will wait for
 		new_block->page.lock.x_unlock(). */
 		block->page.set_state(buf_page_t::READ_FIX);
 
@@ -2954,59 +2951,6 @@ buf_page_get_low(
 	return block;
 }
 
-/** Get access to a database page. Buffered redo log may be applied.
-@param[in]	page_id			page id
-@param[in]	zip_size		ROW_FORMAT=COMPRESSED page size, or 0
-@param[in]	rw_latch		RW_S_LATCH, RW_X_LATCH, RW_NO_LATCH
-@param[in]	guess			guessed block or NULL
-@param[in]	mode			BUF_GET, BUF_GET_IF_IN_POOL,
-or BUF_PEEK_IF_IN_POOL
-@param[in,out]	mtr			mini-transaction, or NULL
-@param[out]	err			DB_SUCCESS or error code
-@return pointer to the block or NULL */
-buf_block_t*
-buf_page_get_gen(
-	const page_id_t		page_id,
-	ulint			zip_size,
-	ulint			rw_latch,
-	buf_block_t*		guess,
-	ulint			mode,
-	mtr_t*			mtr,
-	dberr_t*		err)
-{
-  buf_block_t *block= recv_sys.recover(page_id);
-  if (UNIV_LIKELY(!block))
-    return buf_page_get_low(page_id, zip_size, rw_latch,
-                            guess, mode, mtr, err);
-  else if (UNIV_UNLIKELY(block == reinterpret_cast<buf_block_t*>(-1)))
-  {
-  corrupted:
-    if (err)
-      *err= DB_CORRUPTION;
-    return nullptr;
-  }
-  if (err)
-    *err= DB_SUCCESS;
-  /* Recovery is a special case; we fix() before acquiring lock. */
-  auto s= block->page.fix();
-  ut_ad(s >= buf_page_t::FREED);
-  /* The block may be write-fixed at this point because we are not
-  holding a lock, but it must not be read-fixed. */
-  ut_ad(s < buf_page_t::READ_FIX || s >= buf_page_t::WRITE_FIX);
-  if (s < buf_page_t::UNFIXED)
-  {
-    ut_ad(mode == BUF_GET_POSSIBLY_FREED || mode == BUF_PEEK_IF_IN_POOL);
-    mysql_mutex_lock(&buf_pool.mutex);
-    block->page.unfix();
-    buf_LRU_free_page(&block->page, true);
-    mysql_mutex_unlock(&buf_pool.mutex);
-    goto corrupted;
-  }
-
-  mtr->page_lock(block, rw_latch);
-  return block;
-}
-
 /********************************************************************//**
 This is the general function used to get optimistic access to a database
 page.

storage/innobase/buf/buf0lru.cc

@@ -815,7 +815,7 @@ bool buf_LRU_free_page(buf_page_t *bpage, bool zip)
 
 	/* We must hold an exclusive hash_lock to prevent
 	bpage->can_relocate() from changing due to a concurrent
-	execution of buf_page_get_low(). */
+	execution of buf_page_get_gen(). */
 	buf_pool_t::hash_chain& chain= buf_pool.page_hash.cell_get(id.fold());
 	page_hash_latch& hash_lock = buf_pool.page_hash.lock_get(chain);
 	/* We cannot use transactional_lock_guard here,

storage/innobase/dict/dict0boot.cc

@@ -218,8 +218,7 @@ dberr_t dict_boot()
 	dict_sys.create();
 
 	dberr_t err;
-	const buf_block_t *d = buf_page_get_gen(hdr_page_id, 0, RW_S_LATCH,
-						nullptr, BUF_GET, &mtr, &err);
+	const buf_block_t *d = recv_sys.recover(hdr_page_id, &mtr ,&err);
 	if (!d) {
 		mtr.commit();
 		return err;
@@ -393,19 +392,6 @@ dberr_t dict_boot()
 		UT_BITS_IN_BYTES(unsigned(table->indexes.start->n_nullable)));
 
 	mtr.commit();
-
-	if (err == DB_SUCCESS) {
-		/* Load definitions of other indexes on system tables */
-
-		dict_load_sys_table(dict_sys.sys_tables);
-		dict_load_sys_table(dict_sys.sys_columns);
-		dict_load_sys_table(dict_sys.sys_indexes);
-		dict_load_sys_table(dict_sys.sys_fields);
-		dict_sys.unlock();
-		dict_sys.load_sys_tables();
-	} else {
-		dict_sys.unlock();
-	}
-
+	dict_sys.unlock();
 	return err;
 }

storage/innobase/ibuf/ibuf0ibuf.cc

@@ -1012,8 +1012,7 @@ dberr_t ibuf_upgrade_needed()
   mtr.start();
   mtr.x_lock_space(fil_system.sys_space);
   dberr_t err;
-  const buf_block_t *header_page=
-    buf_page_get_gen(ibuf_header, 0, RW_S_LATCH, nullptr, BUF_GET, &mtr, &err);
+  const buf_block_t *header_page= recv_sys.recover(ibuf_header, &mtr, &err);
 
   if (!header_page)
   {
@@ -1026,8 +1025,7 @@ dberr_t ibuf_upgrade_needed()
     return err;
   }
 
-  const buf_block_t *root= buf_page_get_gen(ibuf_root, 0, RW_S_LATCH, nullptr,
-                                            BUF_GET, &mtr, &err);
+  const buf_block_t *root= recv_sys.recover(ibuf_root, &mtr, &err);
   if (!root)
     goto err_exit;
 

storage/innobase/include/buf0buf.h

@@ -201,34 +201,12 @@ buf_page_get_gen(
 	buf_block_t*		guess,
 	ulint			mode,
 	mtr_t*			mtr,
-	dberr_t*		err = NULL)
-	MY_ATTRIBUTE((nonnull(6)));
-
-/** This is the low level function used to get access to a database page.
-@param[in]	page_id			page id
-@param[in]	zip_size		ROW_FORMAT=COMPRESSED page size, or 0
-@param[in]	rw_latch		RW_S_LATCH, RW_X_LATCH, RW_NO_LATCH
-@param[in]	guess			guessed block or NULL
-@param[in]	mode			BUF_GET, BUF_GET_IF_IN_POOL,
-or BUF_PEEK_IF_IN_POOL
-@param[in,out]	mtr			mini-transaction, or NULL if a
-					block with page_id is to be evicted
-@param[out]	err			DB_SUCCESS or error code
-@return pointer to the block or NULL */
-buf_block_t*
-buf_page_get_low(
-	const page_id_t		page_id,
-	ulint			zip_size,
-	ulint			rw_latch,
-	buf_block_t*		guess,
-	ulint			mode,
-	mtr_t*			mtr,
-	dberr_t*		err);
+	dberr_t*		err = nullptr);
 
 /** Initialize a page in the buffer pool. The page is usually not read
 from a file even if it cannot be found in the buffer buf_pool. This is one
 of the functions which perform to a block a state transition NOT_USED => LRU
-(the other is buf_page_get_low()).
+(the other is buf_page_get_gen()).
 @param[in,out]	space		space object
 @param[in]	offset		offset of the tablespace
 @param[in]	zip_size	ROW_FORMAT=COMPRESSED page size, or 0

storage/innobase/include/log0recv.h

@@ -280,12 +280,6 @@ struct recv_sys_t
   @retval -1      if the page cannot be recovered due to corruption */
   inline buf_block_t *recover_low(const map::iterator &p, mtr_t &mtr,
                                   buf_block_t *b, lsn_t init_lsn);
-  /** Attempt to initialize a page based on redo log records.
-  @param page_id  page identifier
-  @return the recovered block
-  @retval nullptr if the page cannot be initialized based on log records
-  @retval -1      if the page cannot be recovered due to corruption */
-  ATTRIBUTE_COLD buf_block_t *recover_low(const page_id_t page_id);
 
   /** All found log files (multiple ones are possible if we are upgrading
   from before MariaDB Server 10.5.1) */
@@ -430,15 +424,14 @@ struct recv_sys_t
   /** @return whether log file corruption was found */
   bool is_corrupt_log() const { return UNIV_UNLIKELY(found_corrupt_log); }
 
-  /** Attempt to initialize a page based on redo log records.
+  /** Read a page or recover it based on redo log records.
   @param page_id  page identifier
-  @return the recovered block
-  @retval nullptr if the page cannot be initialized based on log records
-  @retval -1      if the page cannot be recovered due to corruption */
-  buf_block_t *recover(const page_id_t page_id)
-  {
-    return UNIV_UNLIKELY(recovery_on) ? recover_low(page_id) : nullptr;
-  }
+  @param mtr      mini-transaction
+  @param err      error code
+  @return the requested block
+  @retval nullptr if the page cannot be accessed due to corruption */
+  ATTRIBUTE_COLD
+  buf_block_t *recover(const page_id_t page_id, mtr_t *mtr, dberr_t *err);
 
   /** Try to recover a tablespace that was not readable earlier
   @param p          iterator

storage/innobase/log/log0recv.cc

@@ -3649,33 +3649,70 @@ inline buf_block_t *recv_sys_t::recover_low(const map::iterator &p, mtr_t &mtr,
   return block ? block : reinterpret_cast<buf_block_t*>(-1);
 }
 
-/** Attempt to initialize a page based on redo log records.
+/** Read a page or recover it based on redo log records.
 @param page_id  page identifier
-@return recovered block
-@retval nullptr if the page cannot be initialized based on log records */
-ATTRIBUTE_COLD buf_block_t *recv_sys_t::recover_low(const page_id_t page_id)
+@param mtr      mini-transaction
+@param err      error code
+@return the requested block
+@retval nullptr if the page cannot be accessed due to corruption */
+ATTRIBUTE_COLD
+buf_block_t *
+recv_sys_t::recover(const page_id_t page_id, mtr_t *mtr, dberr_t *err)
 {
+  if (!recovery_on)
+  must_read:
+    return buf_page_get_gen(page_id, 0, RW_S_LATCH, nullptr, BUF_GET, mtr,
+                            err);
+
   mysql_mutex_lock(&mutex);
   map::iterator p= pages.find(page_id);
 
-  if (p != pages.end() && !p->second.being_processed && p->second.skip_read)
+  if (p == pages.end() || p->second.being_processed || !p->second.skip_read)
   {
-    p->second.being_processed= 1;
-    const lsn_t init_lsn{mlog_init.last(page_id)};
     mysql_mutex_unlock(&mutex);
-    buf_block_t *free_block= buf_LRU_get_free_block(have_no_mutex);
-    mtr_t mtr;
-    buf_block_t *block= recover_low(p, mtr, free_block, init_lsn);
-    p->second.being_processed= -1;
-    ut_ad(!block || block == reinterpret_cast<buf_block_t*>(-1) ||
-          block == free_block);
-    if (UNIV_UNLIKELY(!block))
-      buf_pool.free_block(free_block);
-    return block;
+    goto must_read;
   }
 
+  p->second.being_processed= 1;
+  const lsn_t init_lsn{mlog_init.last(page_id)};
   mysql_mutex_unlock(&mutex);
-  return nullptr;
+  buf_block_t *free_block= buf_LRU_get_free_block(have_no_mutex);
+  buf_block_t *block;
+  {
+    mtr_t local_mtr;
+    block= recover_low(p, local_mtr, free_block, init_lsn);
+  }
+  p->second.being_processed= -1;
+  if (UNIV_UNLIKELY(!block))
+  {
+    buf_pool.free_block(free_block);
+    goto must_read;
+  }
+  else if (block == reinterpret_cast<buf_block_t*>(-1))
+  {
+  corrupted:
+    if (err)
+      *err= DB_CORRUPTION;
+    return nullptr;
+  }
+
+  ut_ad(block == free_block);
+  auto s= block->page.fix();
+  ut_ad(s >= buf_page_t::FREED);
+  /* The block may be write-fixed at this point because we are not
+  holding a latch, but it must not be read-fixed. */
+  ut_ad(s < buf_page_t::READ_FIX || s >= buf_page_t::WRITE_FIX);
+  if (s < buf_page_t::UNFIXED)
+  {
+    mysql_mutex_lock(&buf_pool.mutex);
+    block->page.unfix();
+    buf_LRU_free_page(&block->page, true);
+    mysql_mutex_unlock(&buf_pool.mutex);
+    goto corrupted;
+  }
+
+  mtr->page_lock(block, RW_S_LATCH);
+  return block;
 }
 
 inline fil_space_t *fil_system_t::find(const char *path) const

storage/innobase/row/row0import.cc

@@ -2074,7 +2074,7 @@ dberr_t PageConverter::operator()(buf_block_t* block) UNIV_NOTHROW
 	/* If we already had an old page with matching number
 	in the buffer pool, evict it now, because
 	we no longer evict the pages on DISCARD TABLESPACE. */
-	buf_page_get_low(block->page.id(), get_zip_size(), RW_NO_LATCH,
+	buf_page_get_gen(block->page.id(), get_zip_size(), RW_NO_LATCH,
 			 nullptr, BUF_PEEK_IF_IN_POOL,
 			 nullptr, nullptr);