1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23 * Use is subject to license terms.
24 *
25 * Copyright 2013 Nexenta Systems, Inc.  All rights reserved.
26 */
27
28/*
29 * Utility routines and top-level conflict detection code for NBMAND
30 * locks.
31 */
32
33#include <sys/types.h>
34#include <sys/cmn_err.h>
35#include <sys/debug.h>
36#include <sys/fcntl.h>
37#include <sys/rwlock.h>
38#include <sys/vnode.h>
39#include <sys/vfs.h>
40#include <sys/nbmlock.h>
41
42/*
43 * Enter the critical region for synchronizing I/O requests with lock/share
44 * requests.  "mode" specifies whether the caller intends to update
45 * lock/share state (as opposed to just query it).
46 */
47
48void
49nbl_start_crit(vnode_t *vp, krw_t mode)
50{
51	rw_enter(&vp->v_nbllock, mode);
52}
53
54/*
55 * Leave the critical region.
56 */
57
58void
59nbl_end_crit(vnode_t *vp)
60{
61	rw_exit(&vp->v_nbllock);
62}
63
64/*
65 * Return non-zero if some thread is in the critical region.
66 * Note that this is appropriate for use in ASSERT()s only.
67 */
68
69int
70nbl_in_crit(vnode_t *vp)
71{
72	return (RW_LOCK_HELD(&vp->v_nbllock));
73}
74
75/*
76 * Returns non-zero if we need to look further for an NBMAND lock or
77 * share conflict.
78 */
79/* ARGSUSED */
80int
81nbl_need_check(vnode_t *vp)
82{
83	/*
84	 * Currently we only check if NBMAND locks/shares are allowed on
85	 * the filesystem.  An option for the future would be to have a
86	 * flag on the vnode, though the locking for that can get tricky.
87	 */
88	/* (vp->v_vfsp) && (vp->v_vfsp->vfs_flag & VFS_NBMAND)) */
89	return (0);
90}
91
92/*
93 * Top-level conflict detection routine.  The arguments describe the
94 * operation that is being attempted.  If the operation conflicts with an
95 * existing lock or share reservation, a non-zero value is returned.  If
96 * the operation is allowed, zero is returned.  Note that there is an
97 * implicit argument, which is the process ID of the requester.
98 *
99 * svmand indicates that the file has System V mandatory locking enabled,
100 * so we should look at all record locks, not just NBMAND record locks.
101 * (This is to avoid a deadlock between a process making an I/O request and
102 * a process trying to release a lock.  Instead of letting the first
103 * process block in the filesystem code, we flag a conflict here.)
104 */
105
106int
107nbl_conflict(vnode_t *vp,
108		nbl_op_t op,		/* attempted operation */
109		u_offset_t offset,	/* ignore if not I/O */
110		ssize_t length,		/* ignore if not I/O */
111		int svmand,		/* System V mandatory locking */
112		caller_context_t *ct)	/* caller context */
113{
114	ASSERT(nbl_in_crit(vp));
115	ASSERT(op == NBL_READ || op == NBL_WRITE || op == NBL_RENAME ||
116	    op == NBL_REMOVE || op == NBL_READWRITE);
117
118	if (nbl_share_conflict(vp, op, ct)) {
119		return (1);
120	}
121
122	/*
123	 * If this is not an I/O request, there's no need to check against
124	 * the locks on the file.
125	 */
126	if (op == NBL_REMOVE || op == NBL_RENAME)
127		return (0);
128
129	return (nbl_lock_conflict(vp, op, offset, length, svmand, ct));
130}
131
132/*
133 * Determine if the given file has mode bits for System V mandatory locks.
134 * If there was an error, the errno value is returned.  Otherwise, zero is
135 * returned and *svp is set appropriately (non-zero for mandatory locks,
136 * zero for no mandatory locks).
137 */
138
139int
140nbl_svmand(vnode_t *vp, cred_t *cr, int *svp)
141{
142	struct vattr va;
143	int error;
144
145	va.va_mask = AT_MODE;
146	error = VOP_GETATTR(vp, &va, 0, cr, NULL);
147	if (error != 0)
148		return (error);
149
150	*svp = MANDLOCK(vp, va.va_mode);
151	return (0);
152}
153
154/*
155 * The kernel handles this for us when we actually try I/O.
156 */
157/* ARGSUSED */
158int
159nbl_share_conflict(vnode_t *vp, nbl_op_t op, caller_context_t *ct)
160{
161	return (0);
162}
163
164/*
165 * The kernel handles this for us when we actually try I/O.
166 */
167/* ARGSUSED */
168int
169nbl_lock_conflict(vnode_t *vp, nbl_op_t op, u_offset_t offset,
170		ssize_t length, int svmand, caller_context_t *ct)
171{
172	return (0);
173}
174