/*****************************************************************************

Copyright (c) 2020, Oracle and/or its affiliates. All Rights Reserved.
Copyright (c) 2020, 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, version 2.0, as published by the
Free Software Foundation.

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limited to OpenSSL) that is licensed under separate terms, as designated in a
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of MySQL hereby grant you an additional permission to link the program and
your derivative works with the separately licensed software that they have
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
for more details.

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this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

*****************************************************************************/

#include "buf0block_hint.h"
namespace buf {

TRANSACTIONAL_TARGET
void Block_hint::buffer_fix_block_if_still_valid()
{
  /* To check if m_block belongs to the current buf_pool, we must
  prevent freeing memory while we check, and until we buffer-fix the
  block. For this purpose it is enough to latch any of the many
  latches taken by buf_pool_t::resize().

  Similar to buf_page_optimistic_get(), we must validate
  m_block->page.id() after acquiring the hash_lock, because the object
  may have been freed and not actually attached to buf_pool.page_hash
  at the moment. (The block could have been reused to store a
  different page, and that slice of buf_pool.page_hash could be protected
  by another hash_lock that we are not holding.)

  Finally, we must ensure that the block is not being freed. */
  if (m_block)
  {
    auto &cell= buf_pool.page_hash.cell_get(m_page_id.fold());
    transactional_shared_lock_guard<page_hash_latch> g
      {buf_pool.page_hash.lock_get(cell)};
    if (buf_pool.is_uncompressed(m_block) && m_page_id == m_block->page.id() &&
        m_block->page.frame && m_block->page.in_file())
      m_block->page.fix();
    else
      clear();
  }
}
}  // namespace buf