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
26/*
27 * Utility routines and top-level conflict detection code for NBMAND
28 * locks.
29 */
30
31#include <sys/nbmlock.h>
32#include <sys/rwlock.h>
33#include <sys/vnode.h>
34#include <sys/cmn_err.h>
35#include <sys/types.h>
36#include <sys/fcntl.h>
37#include <sys/vfs.h>
38
39/*
40 * Enter the critical region for synchronizing I/O requests with lock/share
41 * requests.  "mode" specifies whether the caller intends to update
42 * lock/share state (as opposed to just query it).
43 */
44
45void
46nbl_start_crit(vnode_t *vp, krw_t mode)
47{
48	rw_enter(&vp->v_nbllock, mode);
49}
50
51/*
52 * Leave the critical region.
53 */
54
55void
56nbl_end_crit(vnode_t *vp)
57{
58	rw_exit(&vp->v_nbllock);
59}
60
61/*
62 * Return non-zero if some thread is in the critical region.
63 * Note that this is appropriate for use in ASSERT()s only.
64 */
65
66int
67nbl_in_crit(vnode_t *vp)
68{
69	return (RW_LOCK_HELD(&vp->v_nbllock));
70}
71
72/*
73 * Returns non-zero if we need to look further for an NBMAND lock or
74 * share conflict.
75 */
76int
77nbl_need_check(vnode_t *vp)
78{
79	/*
80	 * Currently we only check if NBMAND locks/shares are allowed on
81	 * the filesystem.  An option for the future would be to have a
82	 * flag on the vnode, though the locking for that can get tricky.
83	 */
84	return ((vp->v_vfsp) && (vp->v_vfsp->vfs_flag & VFS_NBMAND));
85}
86
87/*
88 * Top-level conflict detection routine.  The arguments describe the
89 * operation that is being attempted.  If the operation conflicts with an
90 * existing lock or share reservation, a non-zero value is returned.  If
91 * the operation is allowed, zero is returned.  Note that there is an
92 * implicit argument, which is the process ID of the requester.
93 *
94 * svmand indicates that the file has System V mandatory locking enabled,
95 * so we should look at all record locks, not just NBMAND record locks.
96 * (This is to avoid a deadlock between a process making an I/O request and
97 * a process trying to release a lock.  Instead of letting the first
98 * process block in the filesystem code, we flag a conflict here.)
99 */
100
101int
102nbl_conflict(vnode_t *vp,
103		nbl_op_t op,		/* attempted operation */
104		u_offset_t offset,	/* ignore if not I/O */
105		ssize_t length,		/* ignore if not I/O */
106		int svmand,		/* System V mandatory locking */
107		caller_context_t *ct)	/* caller context */
108{
109	ASSERT(nbl_in_crit(vp));
110	ASSERT(op == NBL_READ || op == NBL_WRITE || op == NBL_RENAME ||
111	    op == NBL_REMOVE || op == NBL_READWRITE);
112
113	if (nbl_share_conflict(vp, op, ct)) {
114		return (1);
115	}
116
117	/*
118	 * If this is not an I/O request, there's no need to check against
119	 * the locks on the file.
120	 */
121	if (op == NBL_REMOVE || op == NBL_RENAME)
122		return (0);
123
124	return (nbl_lock_conflict(vp, op, offset, length, svmand, ct));
125}
126
127/*
128 * Determine if the given file has mode bits for System V mandatory locks.
129 * If there was an error, the errno value is returned.  Otherwise, zero is
130 * returned and *svp is set appropriately (non-zero for mandatory locks,
131 * zero for no mandatory locks).
132 */
133
134int
135nbl_svmand(vnode_t *vp, cred_t *cr, int *svp)
136{
137	struct vattr va;
138	int error;
139
140	va.va_mask = AT_MODE;
141	error = VOP_GETATTR(vp, &va, 0, cr, NULL);
142	if (error != 0)
143		return (error);
144
145	*svp = MANDLOCK(vp, va.va_mode);
146	return (0);
147}
148