null_subr.c revision 330897
1/*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1992, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software donated to Berkeley by 8 * Jan-Simon Pendry. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 35 * 36 * $FreeBSD: stable/11/sys/fs/nullfs/null_subr.c 330897 2018-03-14 03:19:51Z eadler $ 37 */ 38 39#include <sys/param.h> 40#include <sys/systm.h> 41#include <sys/kernel.h> 42#include <sys/lock.h> 43#include <sys/rwlock.h> 44#include <sys/malloc.h> 45#include <sys/mount.h> 46#include <sys/proc.h> 47#include <sys/vnode.h> 48 49#include <fs/nullfs/null.h> 50 51/* 52 * Null layer cache: 53 * Each cache entry holds a reference to the lower vnode 54 * along with a pointer to the alias vnode. When an 55 * entry is added the lower vnode is VREF'd. When the 56 * alias is removed the lower vnode is vrele'd. 57 */ 58 59#define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask]) 60 61static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl; 62static struct rwlock null_hash_lock; 63static u_long null_hash_mask; 64 65static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table"); 66MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part"); 67 68static struct vnode * null_hashins(struct mount *, struct null_node *); 69 70/* 71 * Initialise cache headers 72 */ 73int 74nullfs_init(vfsp) 75 struct vfsconf *vfsp; 76{ 77 78 null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH, 79 &null_hash_mask); 80 rw_init(&null_hash_lock, "nullhs"); 81 return (0); 82} 83 84int 85nullfs_uninit(vfsp) 86 struct vfsconf *vfsp; 87{ 88 89 rw_destroy(&null_hash_lock); 90 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask); 91 return (0); 92} 93 94/* 95 * Return a VREF'ed alias for lower vnode if already exists, else 0. 96 * Lower vnode should be locked on entry and will be left locked on exit. 97 */ 98struct vnode * 99null_hashget(mp, lowervp) 100 struct mount *mp; 101 struct vnode *lowervp; 102{ 103 struct null_node_hashhead *hd; 104 struct null_node *a; 105 struct vnode *vp; 106 107 ASSERT_VOP_LOCKED(lowervp, "null_hashget"); 108 109 /* 110 * Find hash base, and then search the (two-way) linked 111 * list looking for a null_node structure which is referencing 112 * the lower vnode. If found, the increment the null_node 113 * reference count (but NOT the lower vnode's VREF counter). 114 */ 115 hd = NULL_NHASH(lowervp); 116 rw_rlock(&null_hash_lock); 117 LIST_FOREACH(a, hd, null_hash) { 118 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { 119 /* 120 * Since we have the lower node locked the nullfs 121 * node can not be in the process of recycling. If 122 * it had been recycled before we grabed the lower 123 * lock it would not have been found on the hash. 124 */ 125 vp = NULLTOV(a); 126 vref(vp); 127 rw_runlock(&null_hash_lock); 128 return (vp); 129 } 130 } 131 rw_runlock(&null_hash_lock); 132 return (NULLVP); 133} 134 135/* 136 * Act like null_hashget, but add passed null_node to hash if no existing 137 * node found. 138 */ 139static struct vnode * 140null_hashins(mp, xp) 141 struct mount *mp; 142 struct null_node *xp; 143{ 144 struct null_node_hashhead *hd; 145 struct null_node *oxp; 146 struct vnode *ovp; 147 148 hd = NULL_NHASH(xp->null_lowervp); 149 rw_wlock(&null_hash_lock); 150 LIST_FOREACH(oxp, hd, null_hash) { 151 if (oxp->null_lowervp == xp->null_lowervp && 152 NULLTOV(oxp)->v_mount == mp) { 153 /* 154 * See null_hashget for a description of this 155 * operation. 156 */ 157 ovp = NULLTOV(oxp); 158 vref(ovp); 159 rw_wunlock(&null_hash_lock); 160 return (ovp); 161 } 162 } 163 LIST_INSERT_HEAD(hd, xp, null_hash); 164 rw_wunlock(&null_hash_lock); 165 return (NULLVP); 166} 167 168static void 169null_destroy_proto(struct vnode *vp, void *xp) 170{ 171 172 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL); 173 VI_LOCK(vp); 174 vp->v_data = NULL; 175 vp->v_vnlock = &vp->v_lock; 176 vp->v_op = &dead_vnodeops; 177 VI_UNLOCK(vp); 178 vgone(vp); 179 vput(vp); 180 free(xp, M_NULLFSNODE); 181} 182 183static void 184null_insmntque_dtr(struct vnode *vp, void *xp) 185{ 186 187 vput(((struct null_node *)xp)->null_lowervp); 188 null_destroy_proto(vp, xp); 189} 190 191/* 192 * Make a new or get existing nullfs node. 193 * Vp is the alias vnode, lowervp is the lower vnode. 194 * 195 * The lowervp assumed to be locked and having "spare" reference. This routine 196 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers" 197 * the caller's "spare" reference to created nullfs vnode. 198 */ 199int 200null_nodeget(mp, lowervp, vpp) 201 struct mount *mp; 202 struct vnode *lowervp; 203 struct vnode **vpp; 204{ 205 struct null_node *xp; 206 struct vnode *vp; 207 int error; 208 209 ASSERT_VOP_LOCKED(lowervp, "lowervp"); 210 KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p", lowervp)); 211 212 /* Lookup the hash firstly. */ 213 *vpp = null_hashget(mp, lowervp); 214 if (*vpp != NULL) { 215 vrele(lowervp); 216 return (0); 217 } 218 219 /* 220 * The insmntque1() call below requires the exclusive lock on 221 * the nullfs vnode. Upgrade the lock now if hash failed to 222 * provide ready to use vnode. 223 */ 224 if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) { 225 KASSERT((MOUNTTONULLMOUNT(mp)->nullm_flags & NULLM_CACHE) != 0, 226 ("lowervp %p is not excl locked and cache is disabled", 227 lowervp)); 228 vn_lock(lowervp, LK_UPGRADE | LK_RETRY); 229 if ((lowervp->v_iflag & VI_DOOMED) != 0) { 230 vput(lowervp); 231 return (ENOENT); 232 } 233 } 234 235 /* 236 * We do not serialize vnode creation, instead we will check for 237 * duplicates later, when adding new vnode to hash. 238 * Note that duplicate can only appear in hash if the lowervp is 239 * locked LK_SHARED. 240 */ 241 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK); 242 243 error = getnewvnode("nullfs", mp, &null_vnodeops, &vp); 244 if (error) { 245 vput(lowervp); 246 free(xp, M_NULLFSNODE); 247 return (error); 248 } 249 250 xp->null_vnode = vp; 251 xp->null_lowervp = lowervp; 252 xp->null_flags = 0; 253 vp->v_type = lowervp->v_type; 254 vp->v_data = xp; 255 vp->v_vnlock = lowervp->v_vnlock; 256 error = insmntque1(vp, mp, null_insmntque_dtr, xp); 257 if (error != 0) 258 return (error); 259 /* 260 * Atomically insert our new node into the hash or vget existing 261 * if someone else has beaten us to it. 262 */ 263 *vpp = null_hashins(mp, xp); 264 if (*vpp != NULL) { 265 vrele(lowervp); 266 null_destroy_proto(vp, xp); 267 return (0); 268 } 269 *vpp = vp; 270 271 return (0); 272} 273 274/* 275 * Remove node from hash. 276 */ 277void 278null_hashrem(xp) 279 struct null_node *xp; 280{ 281 282 rw_wlock(&null_hash_lock); 283 LIST_REMOVE(xp, null_hash); 284 rw_wunlock(&null_hash_lock); 285} 286 287#ifdef DIAGNOSTIC 288 289struct vnode * 290null_checkvp(vp, fil, lno) 291 struct vnode *vp; 292 char *fil; 293 int lno; 294{ 295 struct null_node *a = VTONULL(vp); 296 297#ifdef notyet 298 /* 299 * Can't do this check because vop_reclaim runs 300 * with a funny vop vector. 301 */ 302 if (vp->v_op != null_vnodeop_p) { 303 printf ("null_checkvp: on non-null-node\n"); 304 panic("null_checkvp"); 305 } 306#endif 307 if (a->null_lowervp == NULLVP) { 308 /* Should never happen */ 309 panic("null_checkvp %p", vp); 310 } 311 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK); 312 if (a->null_lowervp->v_usecount < 1) 313 panic ("null with unref'ed lowervp, vp %p lvp %p", 314 vp, a->null_lowervp); 315 VI_UNLOCK(a->null_lowervp); 316#ifdef notyet 317 printf("null %x/%d -> %x/%d [%s, %d]\n", 318 NULLTOV(a), vrefcnt(NULLTOV(a)), 319 a->null_lowervp, vrefcnt(a->null_lowervp), 320 fil, lno); 321#endif 322 return (a->null_lowervp); 323} 324#endif 325