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      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 2007 Sun Microsystems, Inc.  All rights reserved.
     23  * Use is subject to license terms.
     24  */
     25 
     26 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     27 
     28 /*
     29  * Utility routines and top-level conflict detection code for NBMAND
     30  * locks.
     31  */
     32 
     33 #include <sys/nbmlock.h>
     34 #include <sys/rwlock.h>
     35 #include <sys/vnode.h>
     36 #include <sys/cmn_err.h>
     37 #include <sys/types.h>
     38 #include <sys/fcntl.h>
     39 #include <sys/vfs.h>
     40 
     41 /*
     42  * Enter the critical region for synchronizing I/O requests with lock/share
     43  * requests.  "mode" specifies whether the caller intends to update
     44  * lock/share state (as opposed to just query it).
     45  */
     46 
     47 void
     48 nbl_start_crit(vnode_t *vp, krw_t mode)
     49 {
     50 	rw_enter(&vp->v_nbllock, mode);
     51 }
     52 
     53 /*
     54  * Leave the critical region.
     55  */
     56 
     57 void
     58 nbl_end_crit(vnode_t *vp)
     59 {
     60 	rw_exit(&vp->v_nbllock);
     61 }
     62 
     63 /*
     64  * Return non-zero if some thread is in the critical region.
     65  * Note that this is appropriate for use in ASSERT()s only.
     66  */
     67 
     68 int
     69 nbl_in_crit(vnode_t *vp)
     70 {
     71 	return (RW_LOCK_HELD(&vp->v_nbllock));
     72 }
     73 
     74 /*
     75  * Return the nbl_op_t that corresponds to the given lock type (read or
     76  * write).
     77  */
     78 
     79 nbl_op_t
     80 nbl_lock_to_op(int lock_type)
     81 {
     82 	int level;
     83 
     84 	switch (lock_type) {
     85 	case F_WRLCK:
     86 		return (NBL_READWRITE);
     87 	case F_RDLCK:
     88 		return (NBL_READ);
     89 	default:
     90 #ifdef DEBUG
     91 		level = CE_PANIC;
     92 #else
     93 		level = CE_WARN;
     94 #endif
     95 		cmn_err(level, "unexpected lock type: %d\n", lock_type);
     96 		return (NBL_WRITE);	/* pick something restrictive */
     97 	}
     98 	/*NOTREACHED*/
     99 }
    100 
    101 /*
    102  * Returns non-zero if we need to look further for an NBMAND lock or
    103  * share conflict.
    104  */
    105 int
    106 nbl_need_check(vnode_t *vp)
    107 {
    108 	/*
    109 	 * Currently we only check if NBMAND locks/shares are allowed on
    110 	 * the filesystem.  An option for the future would be to have a
    111 	 * flag on the vnode, though the locking for that can get tricky.
    112 	 */
    113 	return ((vp->v_vfsp) && (vp->v_vfsp->vfs_flag & VFS_NBMAND));
    114 }
    115 
    116 /*
    117  * Top-level conflict detection routine.  The arguments describe the
    118  * operation that is being attempted.  If the operation conflicts with an
    119  * existing lock or share reservation, a non-zero value is returned.  If
    120  * the operation is allowed, zero is returned.  Note that there is an
    121  * implicit argument, which is the process ID of the requester.
    122  *
    123  * svmand indicates that the file has System V mandatory locking enabled,
    124  * so we should look at all record locks, not just NBMAND record locks.
    125  * (This is to avoid a deadlock between a process making an I/O request and
    126  * a process trying to release a lock.  Instead of letting the first
    127  * process block in the filesystem code, we flag a conflict here.)
    128  */
    129 
    130 int
    131 nbl_conflict(vnode_t *vp,
    132 		nbl_op_t op,		/* attempted operation */
    133 		u_offset_t offset,	/* ignore if not I/O */
    134 		ssize_t length,		/* ignore if not I/O */
    135 		int svmand,		/* System V mandatory locking */
    136 		caller_context_t *ct)	/* caller context */
    137 {
    138 	ASSERT(nbl_in_crit(vp));
    139 	ASSERT(op == NBL_READ || op == NBL_WRITE || op == NBL_RENAME ||
    140 	    op == NBL_REMOVE || op == NBL_READWRITE);
    141 
    142 	if (nbl_share_conflict(vp, op, ct)) {
    143 		return (1);
    144 	}
    145 
    146 	/*
    147 	 * If this is not an I/O request, there's no need to check against
    148 	 * the locks on the file.
    149 	 */
    150 	if (op == NBL_REMOVE || op == NBL_RENAME)
    151 		return (0);
    152 
    153 	return (nbl_lock_conflict(vp, op, offset, length, svmand, ct));
    154 }
    155 
    156 /*
    157  * Determine if the given file has mode bits for System V mandatory locks.
    158  * If there was an error, the errno value is returned.  Otherwise, zero is
    159  * returned and *svp is set appropriately (non-zero for mandatory locks,
    160  * zero for no mandatory locks).
    161  */
    162 
    163 int
    164 nbl_svmand(vnode_t *vp, cred_t *cr, int *svp)
    165 {
    166 	struct vattr va;
    167 	int error;
    168 
    169 	va.va_mask = AT_MODE;
    170 	error = VOP_GETATTR(vp, &va, 0, cr, NULL);
    171 	if (error != 0)
    172 		return (error);
    173 
    174 	*svp = MANDLOCK(vp, va.va_mode);
    175 	return (0);
    176 }
    177