usr/src/uts/common/fs/nbmlock.c

   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 }