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
45 void
nbl_start_crit(vnode_t * vp,krw_t mode)46 nbl_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
55 void
nbl_end_crit(vnode_t * vp)56 nbl_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
66 int
nbl_in_crit(vnode_t * vp)67 nbl_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 */
76 int
nbl_need_check(vnode_t * vp)77 nbl_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
101 int
nbl_conflict(vnode_t * vp,nbl_op_t op,u_offset_t offset,ssize_t length,int svmand,caller_context_t * ct)102 nbl_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
134 int
nbl_svmand(vnode_t * vp,cred_t * cr,int * svp)135 nbl_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