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