1 /*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software donated to Berkeley by 6 * Jan-Simon Pendry. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 33 * 34 * $FreeBSD$ 35 */ 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/kernel.h> 40 #include <sys/lock.h> 41 #include <sys/mutex.h> 42 #include <sys/malloc.h> 43 #include <sys/mount.h> 44 #include <sys/proc.h> 45 #include <sys/vnode.h> 46 47 #include <fs/nullfs/null.h> 48 49 #define LOG2_SIZEVNODE 8 /* log2(sizeof struct vnode) */ 50 #define NNULLNODECACHE 16 51 52 /* 53 * Null layer cache: 54 * Each cache entry holds a reference to the lower vnode 55 * along with a pointer to the alias vnode. When an 56 * entry is added the lower vnode is VREF'd. When the 57 * alias is removed the lower vnode is vrele'd. 58 */ 59 60 #define NULL_NHASH(vp) \ 61 (&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash]) 62 63 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl; 64 static u_long null_node_hash; 65 struct mtx null_hashmtx; 66 67 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table"); 68 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part"); 69 70 static struct vnode * null_hashins(struct mount *, struct null_node *); 71 72 /* 73 * Initialise cache headers 74 */ 75 int 76 nullfs_init(vfsp) 77 struct vfsconf *vfsp; 78 { 79 80 NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */ 81 null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash); 82 mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF); 83 return (0); 84 } 85 86 int 87 nullfs_uninit(vfsp) 88 struct vfsconf *vfsp; 89 { 90 91 mtx_destroy(&null_hashmtx); 92 hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_node_hash); 93 return (0); 94 } 95 96 /* 97 * Return a VREF'ed alias for lower vnode if already exists, else 0. 98 * Lower vnode should be locked on entry and will be left locked on exit. 99 */ 100 struct vnode * 101 null_hashget(mp, lowervp) 102 struct mount *mp; 103 struct vnode *lowervp; 104 { 105 struct null_node_hashhead *hd; 106 struct null_node *a; 107 struct vnode *vp; 108 109 ASSERT_VOP_LOCKED(lowervp, "null_hashget"); 110 111 /* 112 * Find hash base, and then search the (two-way) linked 113 * list looking for a null_node structure which is referencing 114 * the lower vnode. If found, the increment the null_node 115 * reference count (but NOT the lower vnode's VREF counter). 116 */ 117 hd = NULL_NHASH(lowervp); 118 mtx_lock(&null_hashmtx); 119 LIST_FOREACH(a, hd, null_hash) { 120 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { 121 /* 122 * Since we have the lower node locked the nullfs 123 * node can not be in the process of recycling. If 124 * it had been recycled before we grabed the lower 125 * lock it would not have been found on the hash. 126 */ 127 vp = NULLTOV(a); 128 vref(vp); 129 mtx_unlock(&null_hashmtx); 130 return (vp); 131 } 132 } 133 mtx_unlock(&null_hashmtx); 134 return (NULLVP); 135 } 136 137 /* 138 * Act like null_hashget, but add passed null_node to hash if no existing 139 * node found. 140 */ 141 static struct vnode * 142 null_hashins(mp, xp) 143 struct mount *mp; 144 struct null_node *xp; 145 { 146 struct null_node_hashhead *hd; 147 struct null_node *oxp; 148 struct vnode *ovp; 149 150 hd = NULL_NHASH(xp->null_lowervp); 151 mtx_lock(&null_hashmtx); 152 LIST_FOREACH(oxp, hd, null_hash) { 153 if (oxp->null_lowervp == xp->null_lowervp && 154 NULLTOV(oxp)->v_mount == mp) { 155 /* 156 * See null_hashget for a description of this 157 * operation. 158 */ 159 ovp = NULLTOV(oxp); 160 vref(ovp); 161 mtx_unlock(&null_hashmtx); 162 return (ovp); 163 } 164 } 165 LIST_INSERT_HEAD(hd, xp, null_hash); 166 mtx_unlock(&null_hashmtx); 167 return (NULLVP); 168 } 169 170 static void 171 null_destroy_proto(struct vnode *vp, void *xp) 172 { 173 174 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL); 175 VI_LOCK(vp); 176 vp->v_data = NULL; 177 vp->v_vnlock = &vp->v_lock; 178 vp->v_op = &dead_vnodeops; 179 VI_UNLOCK(vp); 180 vgone(vp); 181 vput(vp); 182 free(xp, M_NULLFSNODE); 183 } 184 185 static void 186 null_insmntque_dtr(struct vnode *vp, void *xp) 187 { 188 189 vput(((struct null_node *)xp)->null_lowervp); 190 null_destroy_proto(vp, xp); 191 } 192 193 /* 194 * Make a new or get existing nullfs node. 195 * Vp is the alias vnode, lowervp is the lower vnode. 196 * 197 * The lowervp assumed to be locked and having "spare" reference. This routine 198 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers" 199 * the caller's "spare" reference to created nullfs vnode. 200 */ 201 int 202 null_nodeget(mp, lowervp, vpp) 203 struct mount *mp; 204 struct vnode *lowervp; 205 struct vnode **vpp; 206 { 207 struct null_node *xp; 208 struct vnode *vp; 209 int error; 210 211 ASSERT_VOP_LOCKED(lowervp, "lowervp"); 212 KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p", lowervp)); 213 214 /* Lookup the hash firstly. */ 215 *vpp = null_hashget(mp, lowervp); 216 if (*vpp != NULL) { 217 vrele(lowervp); 218 return (0); 219 } 220 221 /* 222 * The insmntque1() call below requires the exclusive lock on 223 * the nullfs vnode. Upgrade the lock now if hash failed to 224 * provide ready to use vnode. 225 */ 226 if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) { 227 vn_lock(lowervp, LK_UPGRADE | LK_RETRY); 228 if ((lowervp->v_iflag & VI_DOOMED) != 0) { 229 vput(lowervp); 230 return (ENOENT); 231 } 232 } 233 234 /* 235 * We do not serialize vnode creation, instead we will check for 236 * duplicates later, when adding new vnode to hash. 237 * Note that duplicate can only appear in hash if the lowervp is 238 * locked LK_SHARED. 239 */ 240 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK); 241 242 error = getnewvnode("null", mp, &null_vnodeops, &vp); 243 if (error) { 244 vput(lowervp); 245 free(xp, M_NULLFSNODE); 246 return (error); 247 } 248 249 xp->null_vnode = vp; 250 xp->null_lowervp = lowervp; 251 vp->v_type = lowervp->v_type; 252 vp->v_data = xp; 253 vp->v_vnlock = lowervp->v_vnlock; 254 error = insmntque1(vp, mp, null_insmntque_dtr, xp); 255 if (error != 0) 256 return (error); 257 /* 258 * Atomically insert our new node into the hash or vget existing 259 * if someone else has beaten us to it. 260 */ 261 *vpp = null_hashins(mp, xp); 262 if (*vpp != NULL) { 263 vrele(lowervp); 264 null_destroy_proto(vp, xp); 265 return (0); 266 } 267 *vpp = vp; 268 269 return (0); 270 } 271 272 /* 273 * Remove node from hash. 274 */ 275 void 276 null_hashrem(xp) 277 struct null_node *xp; 278 { 279 280 mtx_lock(&null_hashmtx); 281 LIST_REMOVE(xp, null_hash); 282 mtx_unlock(&null_hashmtx); 283 } 284 285 #ifdef DIAGNOSTIC 286 287 struct vnode * 288 null_checkvp(vp, fil, lno) 289 struct vnode *vp; 290 char *fil; 291 int lno; 292 { 293 struct null_node *a = VTONULL(vp); 294 295 #ifdef notyet 296 /* 297 * Can't do this check because vop_reclaim runs 298 * with a funny vop vector. 299 */ 300 if (vp->v_op != null_vnodeop_p) { 301 printf ("null_checkvp: on non-null-node\n"); 302 panic("null_checkvp"); 303 } 304 #endif 305 if (a->null_lowervp == NULLVP) { 306 /* Should never happen */ 307 panic("null_checkvp %p", vp); 308 } 309 VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK); 310 if (a->null_lowervp->v_usecount < 1) 311 panic ("null with unref'ed lowervp, vp %p lvp %p", 312 vp, a->null_lowervp); 313 VI_UNLOCK(a->null_lowervp); 314 #ifdef notyet 315 printf("null %x/%d -> %x/%d [%s, %d]\n", 316 NULLTOV(a), vrefcnt(NULLTOV(a)), 317 a->null_lowervp, vrefcnt(a->null_lowervp), 318 fil, lno); 319 #endif 320 return (a->null_lowervp); 321 } 322 #endif 323