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 #include <linux/fcntl.h>
  28
  29 #define MLOG_MASK_PREFIX ML_INODE
  30 #include <cluster/masklog.h>
  31
  32 #include "ocfs2.h"
  33
  34 #include "dlmglue.h"
  35 #include "file.h"
  36 #include "inode.h"
  37 #include "locks.h"
  38
  39 static int ocfs2_do_flock(struct file *file, struct inode *inode,
  40                           int cmd, struct file_lock *fl)
  41 {
  42         int ret = 0, level = 0, trylock = 0;
  43         struct ocfs2_file_private *fp = file->private_data;
  44         struct ocfs2_lock_res *lockres = &fp->fp_flock;
  45
  46         if (fl->fl_type == F_WRLCK)
  47                 level = 1;
  48         if (!IS_SETLKW(cmd))
  49                 trylock = 1;
  50
  51         mutex_lock(&fp->fp_mutex);
  52
  53         if (lockres->l_flags & OCFS2_LOCK_ATTACHED &&
  54             lockres->l_level > LKM_NLMODE) {
  55                 int old_level = 0;
  56
  57                 if (lockres->l_level == LKM_EXMODE)
  58                         old_level = 1;
  59
  60                 if (level == old_level)
  61                         goto out;
  62
  63                 /*
  64                  * Converting an existing lock is not guaranteed to be
  65                  * atomic, so we can get away with simply unlocking
  66                  * here and allowing the lock code to try at the new
  67                  * level.
  68                  */
  69
  70                 flock_lock_file_wait(file,
  71                                      &(struct file_lock){.fl_type = F_UNLCK});
  72
  73                 ocfs2_file_unlock(file);
  74         }
  75
  76         ret = ocfs2_file_lock(file, level, trylock);
  77         if (ret) {
  78                 if (ret == -EAGAIN && trylock)
  79                         ret = -EWOULDBLOCK;
  80                 else
  81                         mlog_errno(ret);
  82                 goto out;
  83         }
  84
  85         ret = flock_lock_file_wait(file, fl);
  86
  87 out:
  88         mutex_unlock(&fp->fp_mutex);
  89
  90         return ret;
  91 }
  92
  93 static int ocfs2_do_funlock(struct file *file, int cmd, struct file_lock *fl)
  94 {
  95         int ret;
  96         struct ocfs2_file_private *fp = file->private_data;
  97
  98         mutex_lock(&fp->fp_mutex);
  99         ocfs2_file_unlock(file);
 100         ret = flock_lock_file_wait(file, fl);
 101         mutex_unlock(&fp->fp_mutex);
 102
 103         return ret;
 104 }
 105
 106 /*
 107  * Overall flow of ocfs2_flock() was influenced by gfs2_flock().
 108  */
 109 int ocfs2_flock(struct file *file, int cmd, struct file_lock *fl)
 110 {
 111         struct inode *inode = file->f_mapping->host;
 112         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 113
 114         if (!(fl->fl_flags & FL_FLOCK))
 115                 return -ENOLCK;
 116         if (__mandatory_lock(inode))
 117                 return -ENOLCK;
 118
 119         if ((osb->s_mount_opt & OCFS2_MOUNT_LOCALFLOCKS) ||
 120             ocfs2_mount_local(osb))
 121                 return flock_lock_file_wait(file, fl);
 122
 123         if (fl->fl_type == F_UNLCK)
 124                 return ocfs2_do_funlock(file, cmd, fl);
 125         else
 126                 return ocfs2_do_flock(file, inode, cmd, fl);
 127 }
 128
 129 int ocfs2_lock(struct file *file, int cmd, struct file_lock *fl)
 130 {
 131         struct inode *inode = file->f_mapping->host;
 132         struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 133
 134         if (!(fl->fl_flags & FL_POSIX))
 135                 return -ENOLCK;
 136         if (__mandatory_lock(inode))
 137                 return -ENOLCK;
 138
 139         return ocfs2_plock(osb->cconn, OCFS2_I(inode)->ip_blkno, file, cmd, fl);
 140 }