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#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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