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 * 3. 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 * $FreeBSD$ 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 61 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl; 62 static struct rwlock null_hash_lock; 63 static u_long null_hash_mask; 64 65 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table"); 66 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part"); 67 68 static void null_hashins(struct mount *, struct null_node *); 69 70 /* 71 * Initialise cache headers 72 */ 73 int 74 nullfs_init(struct vfsconf *vfsp) 75 { 76 77 null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH, 78 &null_hash_mask); 79 rw_init(&null_hash_lock, "nullhs"); 80 return (0); 81 } 82 83 int 84 nullfs_uninit(struct vfsconf *vfsp) 85 { 86 87 rw_destroy(&null_hash_lock); 88 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask); 89 return (0); 90 } 91 92 /* 93 * Return a VREF'ed alias for lower vnode if already exists, else 0. 94 * Lower vnode should be locked on entry and will be left locked on exit. 95 */ 96 static struct vnode * 97 null_hashget_locked(struct mount *mp, struct vnode *lowervp) 98 { 99 struct null_node_hashhead *hd; 100 struct null_node *a; 101 struct vnode *vp; 102 103 ASSERT_VOP_LOCKED(lowervp, "null_hashget"); 104 rw_assert(&null_hash_lock, RA_LOCKED); 105 106 /* 107 * Find hash base, and then search the (two-way) linked 108 * list looking for a null_node structure which is referencing 109 * the lower vnode. If found, the increment the null_node 110 * reference count (but NOT the lower vnode's VREF counter). 111 */ 112 hd = NULL_NHASH(lowervp); 113 LIST_FOREACH(a, hd, null_hash) { 114 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { 115 /* 116 * Since we have the lower node locked the nullfs 117 * node can not be in the process of recycling. If 118 * it had been recycled before we grabed the lower 119 * lock it would not have been found on the hash. 120 */ 121 vp = NULLTOV(a); 122 vref(vp); 123 return (vp); 124 } 125 } 126 return (NULLVP); 127 } 128 129 struct vnode * 130 null_hashget(struct mount *mp, struct vnode *lowervp) 131 { 132 struct null_node_hashhead *hd; 133 struct vnode *vp; 134 135 hd = NULL_NHASH(lowervp); 136 if (LIST_EMPTY(hd)) 137 return (NULLVP); 138 139 rw_rlock(&null_hash_lock); 140 vp = null_hashget_locked(mp, lowervp); 141 rw_runlock(&null_hash_lock); 142 143 return (vp); 144 } 145 146 static void 147 null_hashins(struct mount *mp, struct null_node *xp) 148 { 149 struct null_node_hashhead *hd; 150 #ifdef INVARIANTS 151 struct null_node *oxp; 152 #endif 153 154 rw_assert(&null_hash_lock, RA_WLOCKED); 155 156 hd = NULL_NHASH(xp->null_lowervp); 157 #ifdef INVARIANTS 158 LIST_FOREACH(oxp, hd, null_hash) { 159 if (oxp->null_lowervp == xp->null_lowervp && 160 NULLTOV(oxp)->v_mount == mp) { 161 VNASSERT(0, NULLTOV(oxp), 162 ("vnode already in hash")); 163 } 164 } 165 #endif 166 LIST_INSERT_HEAD(hd, xp, null_hash); 167 } 168 169 static void 170 null_destroy_proto(struct vnode *vp, void *xp) 171 { 172 173 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL); 174 VI_LOCK(vp); 175 vp->v_data = NULL; 176 vp->v_vnlock = &vp->v_lock; 177 vp->v_op = &dead_vnodeops; 178 VI_UNLOCK(vp); 179 vgone(vp); 180 vput(vp); 181 free(xp, M_NULLFSNODE); 182 } 183 184 /* 185 * Make a new or get existing nullfs node. 186 * Vp is the alias vnode, lowervp is the lower vnode. 187 * 188 * The lowervp assumed to be locked and having "spare" reference. This routine 189 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers" 190 * the caller's "spare" reference to created nullfs vnode. 191 */ 192 int 193 null_nodeget(struct mount *mp, struct vnode *lowervp, struct vnode **vpp) 194 { 195 struct null_node *xp; 196 struct vnode *vp; 197 int error; 198 199 ASSERT_VOP_LOCKED(lowervp, "lowervp"); 200 VNPASS(lowervp->v_usecount > 0, lowervp); 201 202 /* Lookup the hash firstly. */ 203 *vpp = null_hashget(mp, lowervp); 204 if (*vpp != NULL) { 205 vrele(lowervp); 206 return (0); 207 } 208 209 /* 210 * We do not serialize vnode creation, instead we will check for 211 * duplicates later, when adding new vnode to hash. 212 * Note that duplicate can only appear in hash if the lowervp is 213 * locked LK_SHARED. 214 */ 215 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK); 216 217 error = getnewvnode("nullfs", mp, &null_vnodeops, &vp); 218 if (error) { 219 vput(lowervp); 220 free(xp, M_NULLFSNODE); 221 return (error); 222 } 223 224 VNPASS(vp->v_object == NULL, vp); 225 VNPASS((vn_irflag_read(vp) & VIRF_PGREAD) == 0, vp); 226 227 rw_wlock(&null_hash_lock); 228 xp->null_vnode = vp; 229 xp->null_lowervp = lowervp; 230 xp->null_flags = 0; 231 vp->v_type = lowervp->v_type; 232 vp->v_data = xp; 233 vp->v_vnlock = lowervp->v_vnlock; 234 *vpp = null_hashget_locked(mp, lowervp); 235 if (*vpp != NULL) { 236 rw_wunlock(&null_hash_lock); 237 vrele(lowervp); 238 null_destroy_proto(vp, xp); 239 return (0); 240 } 241 242 /* 243 * We might miss the case where lower vnode sets VIRF_PGREAD 244 * some time after construction, which is typical case. 245 * null_open rechecks. 246 */ 247 if ((vn_irflag_read(lowervp) & VIRF_PGREAD) != 0) { 248 MPASS(lowervp->v_object != NULL); 249 vp->v_object = lowervp->v_object; 250 vn_irflag_set(vp, VIRF_PGREAD); 251 } 252 if (lowervp == MOUNTTONULLMOUNT(mp)->nullm_lowerrootvp) 253 vp->v_vflag |= VV_ROOT; 254 255 error = insmntque1(vp, mp); 256 if (error != 0) { 257 rw_wunlock(&null_hash_lock); 258 vput(lowervp); 259 vp->v_object = NULL; 260 null_destroy_proto(vp, xp); 261 return (error); 262 } 263 264 null_hashins(mp, xp); 265 rw_wunlock(&null_hash_lock); 266 *vpp = vp; 267 268 return (0); 269 } 270 271 /* 272 * Remove node from hash. 273 */ 274 void 275 null_hashrem(struct null_node *xp) 276 { 277 278 rw_wlock(&null_hash_lock); 279 LIST_REMOVE(xp, null_hash); 280 rw_wunlock(&null_hash_lock); 281 } 282 283 #ifdef DIAGNOSTIC 284 285 struct vnode * 286 null_checkvp(struct vnode *vp, char *fil, int lno) 287 { 288 struct null_node *a = VTONULL(vp); 289 290 #ifdef notyet 291 /* 292 * Can't do this check because vop_reclaim runs 293 * with a funny vop vector. 294 */ 295 if (vp->v_op != null_vnodeop_p) { 296 printf ("null_checkvp: on non-null-node\n"); 297 panic("null_checkvp"); 298 } 299 #endif 300 if (a->null_lowervp == NULLVP) { 301 /* Should never happen */ 302 panic("null_checkvp %p", vp); 303 } 304 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK); 305 if (a->null_lowervp->v_usecount < 1) 306 panic ("null with unref'ed lowervp, vp %p lvp %p", 307 vp, a->null_lowervp); 308 VI_UNLOCK(a->null_lowervp); 309 #ifdef notyet 310 printf("null %x/%d -> %x/%d [%s, %d]\n", 311 NULLTOV(a), vrefcnt(NULLTOV(a)), 312 a->null_lowervp, vrefcnt(a->null_lowervp), 313 fil, lno); 314 #endif 315 return (a->null_lowervp); 316 } 317 #endif 318