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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 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
     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
     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
     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
     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
    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
    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