/* -*- mode: c; c-basic-offset: 8; -*-
   * vim: noexpandtab sw=8 ts=8 sts=0:
   *
   * locks.c
   *
   * Userspace file locking support
   *
   * Copyright (C) 2007 Oracle.  All rights reserved.
   *
   * 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; either
   * version 2 of the License, or (at your option) any later version.
   *
   * 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., 59 Temple Place - Suite 330,
   * Boston, MA 021110-1307, USA.
   */
  
  #include <linux/fs.h>
  #include <linux/fcntl.h>
  
  #include <cluster/masklog.h>
  
  #include "ocfs2.h"
  
  #include "dlmglue.h"
  #include "file.h"
  #include "inode.h"
  #include "locks.h"
  
  static int ocfs2_do_flock(struct file *file, struct inode *inode,
  			  int cmd, struct file_lock *fl)
  {
  	int ret = 0, level = 0, trylock = 0;
  	struct ocfs2_file_private *fp = file->private_data;
  	struct ocfs2_lock_res *lockres = &fp->fp_flock;
  
  	if (fl->fl_type == F_WRLCK)
  		level = 1;
  	if (!IS_SETLKW(cmd))
  		trylock = 1;
  
  	mutex_lock(&fp->fp_mutex);
  
  	if (lockres->l_flags & OCFS2_LOCK_ATTACHED &&
  	    lockres->l_level > LKM_NLMODE) {
  		int old_level = 0;
  
  		if (lockres->l_level == LKM_EXMODE)
  			old_level = 1;
  
  		if (level == old_level)
  			goto out;
  
  		/*
  		 * Converting an existing lock is not guaranteed to be
  		 * atomic, so we can get away with simply unlocking
  		 * here and allowing the lock code to try at the new
  		 * level.
  		 */
  
  		flock_lock_file_wait(file,
  				     &(struct file_lock){.fl_type = F_UNLCK});
  
  		ocfs2_file_unlock(file);
  	}
  
  	ret = ocfs2_file_lock(file, level, trylock);
  	if (ret) {
  		if (ret == -EAGAIN && trylock)
  			ret = -EWOULDBLOCK;
  		else
  			mlog_errno(ret);
  		goto out;
  	}
  
  	ret = flock_lock_file_wait(file, fl);
  
  out:
  	mutex_unlock(&fp->fp_mutex);
  
  	return ret;
  }
  
  static int ocfs2_do_funlock(struct file *file, int cmd, struct file_lock *fl)
  {
  	int ret;
  	struct ocfs2_file_private *fp = file->private_data;
  
  	mutex_lock(&fp->fp_mutex);
  	ocfs2_file_unlock(file);
  	ret = flock_lock_file_wait(file, fl);
  	mutex_unlock(&fp->fp_mutex);
  
  	return ret;
  }
  
  /*
   * Overall flow of ocfs2_flock() was influenced by gfs2_flock().
   */
  int ocfs2_flock(struct file *file, int cmd, struct file_lock *fl)
  {
  	struct inode *inode = file->f_mapping->host;
  	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
  
  	if (!(fl->fl_flags & FL_FLOCK))
  		return -ENOLCK;
  	if (__mandatory_lock(inode))
  		return -ENOLCK;
  
  	if ((osb->s_mount_opt & OCFS2_MOUNT_LOCALFLOCKS) ||
  	    ocfs2_mount_local(osb))
  		return flock_lock_file_wait(file, fl);
  
  	if (fl->fl_type == F_UNLCK)
  		return ocfs2_do_funlock(file, cmd, fl);
  	else
  		return ocfs2_do_flock(file, inode, cmd, fl);
  }
  
  int ocfs2_lock(struct file *file, int cmd, struct file_lock *fl)
  {
  	struct inode *inode = file->f_mapping->host;
  	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
  
  	if (!(fl->fl_flags & FL_POSIX))
  		return -ENOLCK;
  	if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
  		return -ENOLCK;
  
  	return ocfs2_plock(osb->cconn, OCFS2_I(inode)->ip_blkno, file, cmd, fl);
  }