linux/fs/ocfs2/locks.c
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   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
  38static 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
  86out:
  87        mutex_unlock(&fp->fp_mutex);
  88
  89        return ret;
  90}
  91
  92static 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 */
 108int 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
 128int 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}
 140
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