Root/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
39static 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
87out:
88    mutex_unlock(&fp->fp_mutex);
89
90    return ret;
91}
92
93static 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 */
109int 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
129int 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) && fl->fl_type != F_UNLCK)
137        return -ENOLCK;
138
139    return ocfs2_plock(osb->cconn, OCFS2_I(inode)->ip_blkno, file, cmd, fl);
140}
141

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