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 35 #include <sys/param.h> 36 #include <sys/systm.h> 37 #include <sys/kernel.h> 38 #include <sys/lock.h> 39 #include <sys/rwlock.h> 40 #include <sys/malloc.h> 41 #include <sys/mount.h> 42 #include <sys/proc.h> 43 #include <sys/vnode.h> 44 45 #include <fs/nullfs/null.h> 46 47 /* 48 * Null layer cache: 49 * Each cache entry holds a reference to the lower vnode 50 * along with a pointer to the alias vnode. When an 51 * entry is added the lower vnode is VREF'd. When the 52 * alias is removed the lower vnode is vrele'd. 53 */ 54 55 #define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask]) 56 57 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl; 58 static struct rwlock null_hash_lock; 59 static u_long null_hash_mask; 60 61 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table"); 62 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part"); 63 64 static void null_hashins(struct mount *, struct null_node *); 65 66 /* 67 * Initialise cache headers 68 */ 69 int 70 nullfs_init(struct vfsconf *vfsp) 71 { 72 73 null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH, 74 &null_hash_mask); 75 rw_init(&null_hash_lock, "nullhs"); 76 return (0); 77 } 78 79 int 80 nullfs_uninit(struct vfsconf *vfsp) 81 { 82 83 rw_destroy(&null_hash_lock); 84 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask); 85 return (0); 86 } 87 88 /* 89 * Return a VREF'ed alias for lower vnode if already exists, else 0. 90 * Lower vnode should be locked on entry and will be left locked on exit. 91 */ 92 static struct vnode * 93 null_hashget_locked(struct mount *mp, struct vnode *lowervp) 94 { 95 struct null_node_hashhead *hd; 96 struct null_node *a; 97 struct vnode *vp; 98 99 ASSERT_VOP_LOCKED(lowervp, "null_hashget"); 100 rw_assert(&null_hash_lock, RA_LOCKED); 101 102 /* 103 * Find hash base, and then search the (two-way) linked 104 * list looking for a null_node structure which is referencing 105 * the lower vnode. If found, the increment the null_node 106 * reference count (but NOT the lower vnode's VREF counter). 107 */ 108 hd = NULL_NHASH(lowervp); 109 LIST_FOREACH(a, hd, null_hash) { 110 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { 111 /* 112 * Since we have the lower node locked the nullfs 113 * node can not be in the process of recycling. If 114 * it had been recycled before we grabed the lower 115 * lock it would not have been found on the hash. 116 */ 117 vp = NULLTOV(a); 118 vref(vp); 119 return (vp); 120 } 121 } 122 return (NULLVP); 123 } 124 125 struct vnode * 126 null_hashget(struct mount *mp, struct vnode *lowervp) 127 { 128 struct null_node_hashhead *hd; 129 struct vnode *vp; 130 131 hd = NULL_NHASH(lowervp); 132 if (LIST_EMPTY(hd)) 133 return (NULLVP); 134 135 rw_rlock(&null_hash_lock); 136 vp = null_hashget_locked(mp, lowervp); 137 rw_runlock(&null_hash_lock); 138 139 return (vp); 140 } 141 142 static void 143 null_hashins(struct mount *mp, struct null_node *xp) 144 { 145 struct null_node_hashhead *hd; 146 #ifdef INVARIANTS 147 struct null_node *oxp; 148 #endif 149 150 rw_assert(&null_hash_lock, RA_WLOCKED); 151 152 hd = NULL_NHASH(xp->null_lowervp); 153 #ifdef INVARIANTS 154 LIST_FOREACH(oxp, hd, null_hash) { 155 if (oxp->null_lowervp == xp->null_lowervp && 156 NULLTOV(oxp)->v_mount == mp) { 157 VNASSERT(0, NULLTOV(oxp), 158 ("vnode already in hash")); 159 } 160 } 161 #endif 162 LIST_INSERT_HEAD(hd, xp, null_hash); 163 } 164 165 static void 166 null_destroy_proto(struct vnode *vp, void *xp) 167 { 168 169 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL); 170 VI_LOCK(vp); 171 vp->v_data = NULL; 172 vp->v_vnlock = &vp->v_lock; 173 vp->v_op = &dead_vnodeops; 174 VI_UNLOCK(vp); 175 vgone(vp); 176 vput(vp); 177 free(xp, M_NULLFSNODE); 178 } 179 180 /* 181 * Make a new or get existing nullfs node. 182 * Vp is the alias vnode, lowervp is the lower vnode. 183 * 184 * The lowervp assumed to be locked and having "spare" reference. This routine 185 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers" 186 * the caller's "spare" reference to created nullfs vnode. 187 */ 188 int 189 null_nodeget(struct mount *mp, struct vnode *lowervp, struct vnode **vpp) 190 { 191 struct null_node *xp; 192 struct vnode *vp; 193 int error; 194 195 ASSERT_VOP_LOCKED(lowervp, "lowervp"); 196 VNPASS(lowervp->v_usecount > 0, lowervp); 197 198 /* Lookup the hash firstly. */ 199 *vpp = null_hashget(mp, lowervp); 200 if (*vpp != NULL) { 201 vrele(lowervp); 202 return (0); 203 } 204 205 /* 206 * We do not serialize vnode creation, instead we will check for 207 * duplicates later, when adding new vnode to hash. 208 * Note that duplicate can only appear in hash if the lowervp is 209 * locked LK_SHARED. 210 */ 211 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK); 212 213 error = getnewvnode("nullfs", mp, &null_vnodeops, &vp); 214 if (error) { 215 vput(lowervp); 216 free(xp, M_NULLFSNODE); 217 return (error); 218 } 219 220 VNPASS(vp->v_object == NULL, vp); 221 VNPASS((vn_irflag_read(vp) & VIRF_PGREAD) == 0, vp); 222 223 rw_wlock(&null_hash_lock); 224 xp->null_vnode = vp; 225 xp->null_lowervp = lowervp; 226 xp->null_flags = 0; 227 vp->v_type = lowervp->v_type; 228 vp->v_data = xp; 229 vp->v_vnlock = lowervp->v_vnlock; 230 *vpp = null_hashget_locked(mp, lowervp); 231 if (*vpp != NULL) { 232 rw_wunlock(&null_hash_lock); 233 vrele(lowervp); 234 null_destroy_proto(vp, xp); 235 return (0); 236 } 237 238 /* 239 * We might miss the case where lower vnode sets VIRF_PGREAD 240 * some time after construction, which is typical case. 241 * null_open rechecks. 242 */ 243 if ((vn_irflag_read(lowervp) & VIRF_PGREAD) != 0) { 244 MPASS(lowervp->v_object != NULL); 245 vp->v_object = lowervp->v_object; 246 vn_irflag_set(vp, VIRF_PGREAD); 247 } 248 if (lowervp == MOUNTTONULLMOUNT(mp)->nullm_lowerrootvp) 249 vp->v_vflag |= VV_ROOT; 250 251 error = insmntque1(vp, mp); 252 if (error != 0) { 253 rw_wunlock(&null_hash_lock); 254 vput(lowervp); 255 vp->v_object = NULL; 256 null_destroy_proto(vp, xp); 257 return (error); 258 } 259 260 null_hashins(mp, xp); 261 vn_set_state(vp, VSTATE_CONSTRUCTED); 262 rw_wunlock(&null_hash_lock); 263 *vpp = vp; 264 265 return (0); 266 } 267 268 /* 269 * Remove node from hash. 270 */ 271 void 272 null_hashrem(struct null_node *xp) 273 { 274 275 rw_wlock(&null_hash_lock); 276 LIST_REMOVE(xp, null_hash); 277 rw_wunlock(&null_hash_lock); 278 } 279 280 #ifdef DIAGNOSTIC 281 282 struct vnode * 283 null_checkvp(struct vnode *vp, char *fil, int lno) 284 { 285 struct null_node *a = VTONULL(vp); 286 287 #ifdef notyet 288 /* 289 * Can't do this check because vop_reclaim runs 290 * with a funny vop vector. 291 */ 292 if (vp->v_op != null_vnodeop_p) { 293 printf ("null_checkvp: on non-null-node\n"); 294 panic("null_checkvp"); 295 } 296 #endif 297 if (a->null_lowervp == NULLVP) { 298 /* Should never happen */ 299 panic("null_checkvp %p", vp); 300 } 301 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK); 302 if (a->null_lowervp->v_usecount < 1) 303 panic ("null with unref'ed lowervp, vp %p lvp %p", 304 vp, a->null_lowervp); 305 VI_UNLOCK(a->null_lowervp); 306 #ifdef notyet 307 printf("null %x/%d -> %x/%d [%s, %d]\n", 308 NULLTOV(a), vrefcnt(NULLTOV(a)), 309 a->null_lowervp, vrefcnt(a->null_lowervp), 310 fil, lno); 311 #endif 312 return (a->null_lowervp); 313 } 314 #endif 315