fs/ocfs2/locks.c

   1 /* -*- mode: c; c-basic-offset: 8; -*-
   2  * vim: noexpandtab sw=8 ts=8 sts=0:
   3  *
   4  * locks.c
   5  *
   6  * Userspace file locking support
   7  *
   8  * Copyright (C) 2007 Oracle.  All rights reserved.
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 2 of the License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public
  21  * License along with this program; if not, write to the
  22  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23  * Boston, MA 021110-1307, USA.
  24  */
  25
  26 #include <linux/fs.h>
  27
  28 #define MLOG_MASK_PREFIX ML_INODE
  29 #include <cluster/masklog.h>
  30
  31 #include "ocfs2.h"
  32
  33 #include "dlmglue.h"
  34 #include "file.h"
  35 #include "locks.h"
  36
  37 static int ocfs2_do_flock(struct file *file, struct inode *inode,
  38                           int cmd, struct file_lock *fl)
  39 {
  40         int ret = 0, level = 0, trylock = 0;
  41         struct ocfs2_file_private *fp = file->private_data;
  42         struct ocfs2_lock_res *lockres = &fp->fp_flock;
  43
  44         if (fl->fl_type == F_WRLCK)
  45                 level = 1;
  46         if (!IS_SETLKW(cmd))
  47                 trylock = 1;
  48
  49         mutex_lock(&fp->fp_mutex);
  50
  51         if (lockres->l_flags & OCFS2_LOCK_ATTACHED &&
  52             lockres->l_level > LKM_NLMODE) {
  53                 int old_level = 0;
  54
  55                 if (lockres->l_level == LKM_EXMODE)
  56                         old_level = 1;
  57
  58                 if (level == old_level)
  59                         goto out;
  60
  61                 /*
  62                  * Converting an existing lock is not guaranteed to be
  63                  * atomic, so we can get away with simply unlocking
  64                  * here and allowing the lock code to try at the new
  65                  * level.
  66                  */
  67
  68                 flock_lock_file_wait(file,
  69                                      &(struct file_lock){.fl_type = F_UNLCK});
  70
  71                 ocfs2_file_unlock(file);
  72         }
  73
  74         ret = ocfs2_file_lock(file, level, trylock);
  75         if (ret) {
  76                 if (ret == -EAGAIN && trylock)
  77                         ret = -EWOULDBLOCK;
  78                 else
  79                         mlog_errno(ret);
  80                 goto out;
  81         }
  82
  83         ret = flock_lock_file_wait(file, fl);
  84
  85 out:
  86         mutex_unlock(&fp->fp_mutex);
  87
  88         return ret;
  89 }
  90
  91 static int ocfs2_do_funlock(struct file *file, int cmd, struct file_lock *fl)
  92 {
  93         int ret;
  94         struct ocfs2_file_private *fp = file->private_data;
  95
  96         mutex_lock(&fp->fp_mutex);
  97         ocfs2_file_unlock(file);
  98         ret = flock_lock_file_wait(file, fl);
  99         mutex_unlock(&fp->fp_mutex);
 100
 101         return ret;
 102 }
 103
 104 /*
 105  * Overall flow of ocfs2_flock() was influenced by gfs2_flock().
 106  */
 107 int ocfs2_flock(struct file *file, int cmd, struct file_lock *fl)
 108 {
 109         struct inode *inode = file->f_mapping->host;
 110         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 111
 112         if (!(fl->fl_flags & FL_FLOCK))
 113                 return -ENOLCK;
 114         if (__mandatory_lock(inode))
 115                 return -ENOLCK;
 116
 117         if ((osb->s_mount_opt & OCFS2_MOUNT_LOCALFLOCKS) ||
 118             ocfs2_mount_local(osb))
 119                 return flock_lock_file_wait(file, fl);
 120
 121         if (fl->fl_type == F_UNLCK)
 122                 return ocfs2_do_funlock(file, cmd, fl);
 123         else
 124                 return ocfs2_do_flock(file, inode, cmd, fl);
 125 }