mi_locking.c

/* Copyright (c) 2000, 2023, Oracle and/or its affiliates.

   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.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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, version 2.0, 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 St, Fifth Floor, Boston, MA 02110-1301  USA */

/*
  locking of isam-tables.
  reads info from a isam-table. Must be first request before doing any furter
  calls to any isamfunktion.  Is used to allow many process use the same
  isamdatabase.
*/

#include "ftdefs.h"

	/* lock table by F_UNLCK, F_RDLCK or F_WRLCK */

int mi_lock_database(MI_INFO *info, int lock_type)
{
  int error;
  uint count;
  MYISAM_SHARE *share=info->s;
  DBUG_ENTER("mi_lock_database");
  DBUG_PRINT("enter",("lock_type: %d  old lock %d  r_locks: %u  w_locks: %u "
                      "global_changed:  %d  open_count: %u  name: '%s'",
                      lock_type, info->lock_type, share->r_locks,
                      share->w_locks,
                      share->global_changed, share->state.open_count,
                      share->index_file_name));
  if (share->options & HA_OPTION_READ_ONLY_DATA ||
      info->lock_type == lock_type)
    DBUG_RETURN(0);
  if (lock_type == F_EXTRA_LCK)                 /* Used by TMP tables */
  {
    ++share->w_locks;
    ++share->tot_locks;
    info->lock_type= lock_type;
    info->s->in_use= list_add(info->s->in_use, &info->in_use);
    DBUG_RETURN(0);
  }

  error= 0;
  mysql_mutex_lock(&share->intern_lock);
  if (share->kfile >= 0)		/* May only be false on windows */
  {
    switch (lock_type) {
    case F_UNLCK:
      ftparser_call_deinitializer(info);
      if (info->lock_type == F_RDLCK)
	count= --share->r_locks;
      else
	count= --share->w_locks;
      --share->tot_locks;
      if (info->lock_type == F_WRLCK && !share->w_locks &&
	  !share->delay_key_write && flush_key_blocks(share->key_cache,
                                                      keycache_thread_var(),
						      share->kfile,FLUSH_KEEP))
      {
	error=my_errno();
        mi_print_error(info->s, HA_ERR_CRASHED);
	mi_mark_crashed(info);		/* Mark that table must be checked */
      }
      if (info->opt_flag & (READ_CACHE_USED | WRITE_CACHE_USED))
      {
	if (end_io_cache(&info->rec_cache))
	{
	  error=my_errno();
          mi_print_error(info->s, HA_ERR_CRASHED);
	  mi_mark_crashed(info);
	}
      }
      if (!count)
      {
	DBUG_PRINT("info",("changed: %u  w_locks: %u",
			   (uint) share->changed, share->w_locks));
	if (share->changed && !share->w_locks)
	{
          if ((info->s->mmaped_length != info->s->state.state.data_file_length) &&
              (info->s->nonmmaped_inserts > MAX_NONMAPPED_INSERTS))
          {
            if (info->s->concurrent_insert)
              mysql_rwlock_wrlock(&info->s->mmap_lock);
            mi_remap_file(info, info->s->state.state.data_file_length);
            info->s->nonmmaped_inserts= 0;
            if (info->s->concurrent_insert)
              mysql_rwlock_unlock(&info->s->mmap_lock);
          }
	  share->state.process= share->last_process=share->this_process;
	  share->state.unique=   info->last_unique=  info->this_unique;
	  share->state.update_count= info->last_loop= ++info->this_loop;
          if (mi_state_info_write(share->kfile, &share->state, 1))
	    error=my_errno();
	  share->changed=0;
	  if (myisam_flush)
	  {
            if (share->file_map)
              my_msync(info->dfile, share->file_map, share->mmaped_length, MS_SYNC);

            if (mysql_file_sync(share->kfile, MYF(0)))
	      error= my_errno();
            if (mysql_file_sync(info->dfile, MYF(0)))
	      error= my_errno();
	  }
	  else
	    share->not_flushed=1;
	  if (error)
          {
            mi_print_error(info->s, HA_ERR_CRASHED);
	    mi_mark_crashed(info);
          }
	}
	if (info->lock_type != F_EXTRA_LCK)
	{
	  if (share->r_locks)
	  {					/* Only read locks left */
	    if (my_lock(share->kfile,F_RDLCK,0L,F_TO_EOF,
			MYF(MY_WME | MY_SEEK_NOT_DONE)) && !error)
	      error=my_errno();
	  }
	  else if (!share->w_locks)
	  {					/* No more locks */
	    if (my_lock(share->kfile,F_UNLCK,0L,F_TO_EOF,
			MYF(MY_WME | MY_SEEK_NOT_DONE)) && !error)
	      error=my_errno();
	  }
	}
      }
      info->opt_flag&= ~(READ_CACHE_USED | WRITE_CACHE_USED);
      info->lock_type= F_UNLCK;
      info->s->in_use= list_delete(info->s->in_use, &info->in_use);
      break;
    case F_RDLCK:
      if (info->lock_type == F_WRLCK)
      {
        /*
          Change RW to READONLY

          mysqld does not turn write locks to read locks,
          so we're never here in mysqld.
        */
	if (share->w_locks == 1)
	{
          if (my_lock(share->kfile,lock_type,0L,F_TO_EOF,
		      MYF(MY_SEEK_NOT_DONE)))
	  {
	    error=my_errno();
	    break;
	  }
	}
	share->w_locks--;
	share->r_locks++;
	info->lock_type=lock_type;
	break;
      }
      if (!share->r_locks && !share->w_locks)
      {
	if (my_lock(share->kfile,lock_type,0L,F_TO_EOF,
		    info->lock_wait | MY_SEEK_NOT_DONE))
	{
	  error=my_errno();
	  break;
	}
	if (mi_state_info_read_dsk(share->kfile, &share->state, 1))
	{
	  error=my_errno();
	  (void) my_lock(share->kfile,F_UNLCK,0L,F_TO_EOF,MYF(MY_SEEK_NOT_DONE));
	  set_my_errno(error);
	  break;
	}
      }
      (void) _mi_test_if_changed(info);
      share->r_locks++;
      share->tot_locks++;
      info->lock_type=lock_type;
      info->s->in_use= list_add(info->s->in_use, &info->in_use);
      break;
    case F_WRLCK:
      if (info->lock_type == F_RDLCK)
      {						/* Change READONLY to RW */
	if (share->r_locks == 1)
	{
	  if (my_lock(share->kfile,lock_type,0L,F_TO_EOF,
		      MYF(info->lock_wait | MY_SEEK_NOT_DONE)))
	  {
	    error=my_errno();
	    break;
	  }
	  share->r_locks--;
	  share->w_locks++;
	  info->lock_type=lock_type;
	  break;
	}
      }
      if (!(share->options & HA_OPTION_READ_ONLY_DATA))
      {
	if (!share->w_locks)
	{
	  if (my_lock(share->kfile,lock_type,0L,F_TO_EOF,
		      info->lock_wait | MY_SEEK_NOT_DONE))
	  {
	    error=my_errno();
	    break;
	  }
	  if (!share->r_locks)
	  {
	    if (mi_state_info_read_dsk(share->kfile, &share->state, 1))
	    {
	      error=my_errno();
	      (void) my_lock(share->kfile,F_UNLCK,0L,F_TO_EOF,
			   info->lock_wait | MY_SEEK_NOT_DONE);
	      set_my_errno(error);
	      break;
	    }
	  }
	}
      }
      (void) _mi_test_if_changed(info);
        
      info->lock_type=lock_type;
      info->invalidator=info->s->invalidator;
      share->w_locks++;
      share->tot_locks++;

      DBUG_EXECUTE_IF("simulate_incorrect_share_wlock_value",
                      DEBUG_SYNC_C("after_share_wlock_increment"););

      info->s->in_use= list_add(info->s->in_use, &info->in_use);
      break;
    default:
      break;				/* Impossible */
    }
  }
#ifdef _WIN32
  else
  {
    /*
       Check for bad file descriptors if this table is part
       of a merge union. Failing to capture this may cause
       a crash on windows if the table is renamed and 
       later on referenced by the merge table.
     */
    if( info->owned_by_merge && (info->s)->kfile < 0 )
    {
      error = HA_ERR_NO_SUCH_TABLE;
    }
  }
#endif
  mysql_mutex_unlock(&share->intern_lock);
  DBUG_RETURN(error);
} /* mi_lock_database */


/****************************************************************************
  The following functions are called by thr_lock() in threaded applications
****************************************************************************/

/*
  Create a copy of the current status for the table

  SYNOPSIS
    mi_get_status()
    param		Pointer to Myisam handler
    concurrent_insert	Set to 1 if we are going to do concurrent inserts
			(THR_WRITE_CONCURRENT_INSERT was used)
*/

void mi_get_status(void* param, int concurrent_insert)
{
  MI_INFO *info=(MI_INFO*) param;
  DBUG_ENTER("mi_get_status");
  DBUG_PRINT("info",("key_file: %ld  data_file: %ld  concurrent_insert: %d",
		     (long) info->s->state.state.key_file_length,
		     (long) info->s->state.state.data_file_length,
                     concurrent_insert));
#ifndef NDEBUG
  if (info->state->key_file_length > info->s->state.state.key_file_length ||
      info->state->data_file_length > info->s->state.state.data_file_length)
    DBUG_PRINT("warning",("old info:  key_file: %ld  data_file: %ld",
			  (long) info->state->key_file_length,
			  (long) info->state->data_file_length));
#endif
  info->save_state=info->s->state.state;
  info->state= &info->save_state;
  info->append_insert_at_end= concurrent_insert;
  if (concurrent_insert)
    info->s->state.state.uncacheable= TRUE;
  DBUG_VOID_RETURN;
}


void mi_update_status(void* param)
{
  MI_INFO *info=(MI_INFO*) param;
  /*
    Because someone may have closed the table we point at, we only
    update the state if its our own state.  This isn't a problem as
    we are always pointing at our own lock or at a read lock.
    (This is enforced by thr_multi_lock.c)
  */
  if (info->state == &info->save_state)
  {
#ifndef NDEBUG
    DBUG_PRINT("info",("updating status:  key_file: %ld  data_file: %ld",
		       (long) info->state->key_file_length,
		       (long) info->state->data_file_length));
    if (info->state->key_file_length < info->s->state.state.key_file_length ||
	info->state->data_file_length < info->s->state.state.data_file_length)
      DBUG_PRINT("warning",("old info:  key_file: %ld  data_file: %ld",
			    (long) info->s->state.state.key_file_length,
			    (long) info->s->state.state.data_file_length));
#endif
    info->s->state.state= *info->state;
  }
  info->state= &info->s->state.state;
  info->append_insert_at_end= 0;

  /*
    We have to flush the write cache here as other threads may start
    reading the table before mi_lock_database() is called
  */
  if (info->opt_flag & WRITE_CACHE_USED)
  {
    if (end_io_cache(&info->rec_cache))
    {
      mi_print_error(info->s, HA_ERR_CRASHED);
      mi_mark_crashed(info);
    }
    info->opt_flag&= ~WRITE_CACHE_USED;
  }
}


void mi_restore_status(void *param)
{
  MI_INFO *info= (MI_INFO*) param;
  info->state= &info->s->state.state;
  info->append_insert_at_end= 0;
}


void mi_copy_status(void* to,void *from)
{
  ((MI_INFO*) to)->state= &((MI_INFO*) from)->save_state;
}


/*
  Check if should allow concurrent inserts

  IMPLEMENTATION
    Allow concurrent inserts if we don't have a hole in the table or
    if there is no active write lock and there is active read locks and 
    myisam_concurrent_insert == 2. In this last case the new
    row('s) are inserted at end of file instead of filling up the hole.

    The last case is to allow one to inserts into a heavily read-used table
    even if there is holes.

  NOTES
    If there is a an rtree indexes in the table, concurrent inserts are
    disabled in mi_open()

  RETURN
    0  ok to use concurrent inserts
    1  not ok
*/

my_bool mi_check_status(void *param)
{
  MI_INFO *info=(MI_INFO*) param;
  /*
    The test for w_locks == 1 is here because this thread has already done an
    external lock (in other words: w_locks == 1 means no other threads has
    a write lock)
  */
  DBUG_PRINT("info",("dellink: %ld  r_locks: %u  w_locks: %u",
                     (long) info->s->state.dellink, (uint) info->s->r_locks,
                     (uint) info->s->w_locks));
  return (my_bool) !(info->s->state.dellink == HA_OFFSET_ERROR ||
                     (myisam_concurrent_insert == 2 && info->s->r_locks &&
                      info->s->w_locks == 1));
}


/****************************************************************************
 ** functions to read / write the state
****************************************************************************/

int _mi_readinfo(MI_INFO *info, int lock_type, int check_keybuffer)
{
  DBUG_ENTER("_mi_readinfo");

  if (info->lock_type == F_UNLCK)
  {
    MYISAM_SHARE *share=info->s;
    if (!share->tot_locks)
    {
      if (my_lock(share->kfile,lock_type,0L,F_TO_EOF,
		  info->lock_wait | MY_SEEK_NOT_DONE))
	DBUG_RETURN(1);
      if (mi_state_info_read_dsk(share->kfile, &share->state, 1))
      {
	int error=my_errno() ? my_errno() : -1;
	(void) my_lock(share->kfile,F_UNLCK,0L,F_TO_EOF,
		     MYF(MY_SEEK_NOT_DONE));
	set_my_errno(error);
	DBUG_RETURN(1);
      }
    }
    if (check_keybuffer)
      (void) _mi_test_if_changed(info);
    info->invalidator=info->s->invalidator;
  }
  else if (lock_type == F_WRLCK && info->lock_type == F_RDLCK)
  {
    set_my_errno(EACCES);				/* Not allowed to change */
    DBUG_RETURN(-1);				/* when have read_lock() */
  }
  DBUG_RETURN(0);
} /* _mi_readinfo */


/*
  Every isam-function that uppdates the isam-database MUST end with this
  request
*/

int _mi_writeinfo(MI_INFO *info, uint operation)
{
  int error,olderror;
  MYISAM_SHARE *share=info->s;
  DBUG_ENTER("_mi_writeinfo");
  DBUG_PRINT("info",("operation: %u  tot_locks: %u", operation,
		     share->tot_locks));

  error=0;
  if (share->tot_locks == 0)
  {
    olderror=my_errno();			/* Remember last error */
    if (operation)
    {					/* Two threads can't be here */
      share->state.process= share->last_process=   share->this_process;
      share->state.unique=  info->last_unique=	   info->this_unique;
      share->state.update_count= info->last_loop= ++info->this_loop;
      if ((error=mi_state_info_write(share->kfile, &share->state, 1)))
	olderror=my_errno();
#ifdef _WIN32
      if (myisam_flush)
      {
        if (share->file_map)
          my_msync(info->dfile, share->file_map, share->mmaped_length, MS_SYNC);
        mysql_file_sync(share->kfile, 0);
        mysql_file_sync(info->dfile, 0);
      }
#endif
    }
    if (!(operation & WRITEINFO_NO_UNLOCK) &&
	my_lock(share->kfile,F_UNLCK,0L,F_TO_EOF,
		MYF(MY_WME | MY_SEEK_NOT_DONE)) && !error)
      DBUG_RETURN(1);
    set_my_errno(olderror);
  }
  else if (operation)
    share->changed= 1;			/* Mark keyfile changed */
  DBUG_RETURN(error);
} /* _mi_writeinfo */


	/* Test if someone has changed the database */
	/* (Should be called after readinfo) */

int _mi_test_if_changed(MI_INFO *info)
{
  MYISAM_SHARE *share=info->s;
  if (share->state.process != share->last_process ||
      share->state.unique  != info->last_unique ||
      share->state.update_count != info->last_loop)
  {						/* Keyfile has changed */
    DBUG_PRINT("info",("index file changed"));
    if (share->state.process != share->this_process)
      (void) flush_key_blocks(share->key_cache, keycache_thread_var(),
                              share->kfile, FLUSH_RELEASE);
    share->last_process=share->state.process;
    info->last_unique=	share->state.unique;
    info->last_loop=	share->state.update_count;
    info->update|=	HA_STATE_WRITTEN;	/* Must use file on next */
    info->data_changed= 1;			/* For mi_is_changed */
    return 1;
  }
  return (!(info->update & HA_STATE_AKTIV) ||
	  (info->update & (HA_STATE_WRITTEN | HA_STATE_DELETED |
			   HA_STATE_KEY_CHANGED)));
} /* _mi_test_if_changed */


/*
  Put a mark in the .MYI file that someone is updating the table


  DOCUMENTATION

  state.open_count in the .MYI file is used the following way:
  - For the first change of the .MYI file in this process open_count is
    incremented by mi_mark_file_change(). (We have a write lock on the file
    when this happens)
  - In mi_close() it's decremented by _mi_decrement_open_count() if it
    was incremented in the same process.

  This mean that if we are the only process using the file, the open_count
  tells us if the MYISAM file wasn't properly closed. (This is true if
  my_disable_locking is set).
*/


int _mi_mark_file_changed(MI_INFO *info)
{
  uchar buff[3];
  MYISAM_SHARE *share=info->s;
  DBUG_ENTER("_mi_mark_file_changed");

  if (!(share->state.changed & STATE_CHANGED) || ! share->global_changed)
  {
    share->state.changed|=(STATE_CHANGED | STATE_NOT_ANALYZED |
			   STATE_NOT_OPTIMIZED_KEYS);
    if (!share->global_changed)
    {
      share->global_changed=1;
      share->state.open_count++;
    }
    if (!share->temporary)
    {
      mi_int2store(buff,share->state.open_count);
      buff[2]=1;				/* Mark that it's changed */
      DBUG_RETURN(mysql_file_pwrite(share->kfile, buff, sizeof(buff),
                                    sizeof(share->state.header),
                                    MYF(MY_NABP)));
    }
  }
  DBUG_RETURN(0);
}


/*
  This is only called by close or by extra(HA_FLUSH) if the OS has the pwrite()
  call.  In these context the following code should be safe!
 */

int _mi_decrement_open_count(MI_INFO *info)
{
  uchar buff[2];
  MYISAM_SHARE *share=info->s;
  int lock_error=0,write_error=0;
  if (share->global_changed)
  {
    uint old_lock=info->lock_type;
    share->global_changed=0;
    lock_error=mi_lock_database(info,F_WRLCK);
    /* Its not fatal even if we couldn't get the lock ! */
    if (share->state.open_count > 0)
    {
      share->state.open_count--;
      mi_int2store(buff,share->state.open_count);
      write_error= mysql_file_pwrite(share->kfile, buff, sizeof(buff),
                                     sizeof(share->state.header),
                                     MYF(MY_NABP));
    }
    if (!lock_error)
      lock_error=mi_lock_database(info,old_lock);
  }
  return MY_TEST(lock_error || write_error);
}