Function key_cache_write

mysys/mf_keycache.c:2979–3289

*/

int key_cache_write(KEY_CACHE *keycache,
                    File file, my_off_t filepos, int level,
                    uchar *buff, uint length,
                    uint block_length  __attribute__((unused)),
                    int dont_write)
{
  my_bool locked_and_incremented= FALSE;
  int error=0;
  DBUG_ENTER("key_cache_write");
  DBUG_PRINT("enter",
             ("fd: %u  pos: %lu  length: %u  block_length: %u"
              "  key_block_length: %u",
              (uint) file, (ulong) filepos, length, block_length,
              keycache ? keycache->key_cache_block_size : 0));

  if (!dont_write)
  {
    /* purecov: begin inspected */
    /* Not used in the server. */
    /* Force writing from buff into disk. */
    keycache->global_cache_w_requests++;
    keycache->global_cache_write++;
    if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL)))
      DBUG_RETURN(1);
    /* purecov: end */
  }

#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
  DBUG_EXECUTE("check_keycache",
               test_key_cache(keycache, "start of key_cache_write", 1););
#endif

  if (keycache->key_cache_inited)
  {
    /* Key cache is used */
    reg1 BLOCK_LINK *block;
    uint read_length;
    uint offset;
    int page_st;

    if (MYSQL_KEYCACHE_WRITE_START_ENABLED())
    {
      MYSQL_KEYCACHE_WRITE_START(my_filename(file), length,
                                 (ulong) (keycache->blocks_used *
                                          keycache->key_cache_block_size),
                                 (ulong) (keycache->blocks_unused *
                                          keycache->key_cache_block_size));
    }

    /*
      When the key cache is once initialized, we use the cache_lock to
      reliably distinguish the cases of normal operation, resizing, and
      disabled cache. We always increment and decrement
      'cnt_for_resize_op' so that a resizer can wait for pending I/O.
    */
    keycache_pthread_mutex_lock(&keycache->cache_lock);
    /*
      Cache resizing has two phases: Flushing and re-initializing. In