1 files changed, 170 insertions, 0 deletions
diff --git a/storage/innobase/include/buf0dblwr.h b/storage/innobase/include/buf0dblwr.h
new file mode 100644
index 00000000..fb9df555
--- /dev/null
+++ b/storage/innobase/include/buf0dblwr.h
@@ -0,0 +1,170 @@
+/*****************************************************************************
+
+Copyright (c) 1995, 2017, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2017, 2020, 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
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
+
+*****************************************************************************/
+
+/**************************************************//**
+@file include/buf0dblwr.h
+Doublewrite buffer module
+
+Created 2011/12/19 Inaam Rana
+*******************************************************/
+
+#pragma once
+
+#include "os0file.h"
+#include "buf0types.h"
+
+/** Doublewrite control struct */
+class buf_dblwr_t
+{
+  struct element
+  {
+    /** asynchronous write request */
+    IORequest request;
+    /** payload size in bytes */
+    size_t size;
+  };
+
+  struct slot
+  {
+    /** first free position in write_buf measured in units of
+     * srv_page_size */
+    ulint first_free;
+    /** number of slots reserved for the current write batch */
+    ulint reserved;
+    /** the doublewrite buffer, aligned to srv_page_size */
+    byte* write_buf;
+    /** buffer blocks to be written via write_buf */
+    element* buf_block_arr;
+  };
+
+  /** the page number of the first doublewrite block (block_size() pages) */
+  page_id_t block1= page_id_t(0, 0);
+  /** the page number of the second doublewrite block (block_size() pages) */
+  page_id_t block2= page_id_t(0, 0);
+
+  /** mutex protecting the data members below */
+  mysql_mutex_t mutex;
+  /** condition variable for !batch_running */
+  pthread_cond_t cond;
+  /** whether a batch is being written from the doublewrite buffer */
+  bool batch_running;
+  /** number of expected flush_buffered_writes_completed() calls */
+  unsigned flushing_buffered_writes;
+  /** pages submitted to flush_buffered_writes() */
+  ulint pages_submitted;
+  /** number of flush_buffered_writes_completed() calls */
+  ulint writes_completed;
+  /** number of pages written by flush_buffered_writes_completed() */
+  ulint pages_written;
+
+  slot slots[2];
+  slot *active_slot= &slots[0];
+
+  /** Initialize the doublewrite buffer data structure.
+  @param header   doublewrite page header in the TRX_SYS page */
+  inline void init(const byte *header);
+
+  /** Flush possible buffered writes to persistent storage. */
+  bool flush_buffered_writes(const ulint size);
+
+public:
+  /** Create or restore the doublewrite buffer in the TRX_SYS page.
+  @return whether the operation succeeded */
+  bool create();
+  /** Free the doublewrite buffer. */
+  void close();
+
+  /** Acquire the mutex */
+  void lock() { mysql_mutex_lock(&mutex); }
+  /** @return the number of submitted page writes */
+  ulint submitted() const
+  { mysql_mutex_assert_owner(&mutex); return pages_submitted; }
+  /** @return the number of completed batches */
+  ulint batches() const
+  { mysql_mutex_assert_owner(&mutex); return writes_completed; }
+  /** @return the number of final pages written */
+  ulint written() const
+  { mysql_mutex_assert_owner(&mutex); return pages_written; }
+  /** Release the mutex */
+  void unlock() { mysql_mutex_unlock(&mutex); }
+
+  /** Initialize the doublewrite buffer memory structure on recovery.
+  If we are upgrading from a version before MySQL 4.1, then this
+  function performs the necessary update operations to support
+  innodb_file_per_table. If we are in a crash recovery, this function
+  loads the pages from double write buffer into memory.
+  @param file File handle
+  @param path Path name of file
+  @return DB_SUCCESS or error code */
+  dberr_t init_or_load_pages(pfs_os_file_t file, const char *path);
+
+  /** Process and remove the double write buffer pages for all tablespaces. */
+  void recover();
+
+  /** Update the doublewrite buffer on data page write completion. */
+  void write_completed();
+  /** Flush possible buffered writes to persistent storage.
+  It is very important to call this function after a batch of writes has been
+  posted, and also when we may have to wait for a page latch!
+  Otherwise a deadlock of threads can occur. */
+  void flush_buffered_writes();
+  /** Update the doublewrite buffer on write batch completion
+  @param request  the completed batch write request */
+  void flush_buffered_writes_completed(const IORequest &request);
+
+  /** Size of the doublewrite block in pages */
+  uint32_t block_size() const { return FSP_EXTENT_SIZE; }
+
+  /** Schedule a page write. If the doublewrite memory buffer is full,
+  flush_buffered_writes() will be invoked to make space.
+  @param request    asynchronous write request
+  @param size       payload size in bytes */
+  void add_to_batch(const IORequest &request, size_t size);
+
+  /** Determine whether the doublewrite buffer is initialized */
+  bool is_initialised() const
+  { return UNIV_LIKELY(block1 != page_id_t(0, 0)); }
+
+  /** @return whether a page identifier is part of the doublewrite buffer */
+  bool is_inside(const page_id_t id) const
+  {
+    if (!is_initialised())
+      return false;
+    ut_ad(block1 < block2);
+    if (id < block1)
+      return false;
+    const uint32_t size= block_size();
+    return id < block1 + size || (id >= block2 && id < block2 + size);
+  }
+
+  /** Wait for flush_buffered_writes() to be fully completed */
+  void wait_flush_buffered_writes()
+  {
+    if (is_initialised())
+    {
+      mysql_mutex_lock(&mutex);
+      while (batch_running)
+        my_cond_wait(&cond, &mutex.m_mutex);
+      mysql_mutex_unlock(&mutex);
+    }
+  }
+};
+
+/** The doublewrite buffer */
+extern buf_dblwr_t buf_dblwr;