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 /* 50 * Null layer cache: 51 * Each cache entry holds a reference to the lower vnode 52 * along with a pointer to the alias vnode. When an 53 * entry is added the lower vnode is VREF'd. When the 54 * alias is removed the lower vnode is vrele'd. 55 */ 56 57 #define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask]) 58 59 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl; 60 static struct mtx null_hashmtx; 61 static u_long null_hash_mask; 62 63 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table"); 64 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part"); 65 66 static struct vnode * null_hashins(struct mount *, struct null_node *); 67 68 /* 69 * Initialise cache headers 70 */ 71 int 72 nullfs_init(vfsp) 73 struct vfsconf *vfsp; 74 { 75 76 null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH, 77 &null_hash_mask); 78 mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF); 79 return (0); 80 } 81 82 int 83 nullfs_uninit(vfsp) 84 struct vfsconf *vfsp; 85 { 86 87 mtx_destroy(&null_hashmtx); 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 struct vnode * 97 null_hashget(mp, lowervp) 98 struct mount *mp; 99 struct vnode *lowervp; 100 { 101 struct null_node_hashhead *hd; 102 struct null_node *a; 103 struct vnode *vp; 104 105 ASSERT_VOP_LOCKED(lowervp, "null_hashget"); 106 107 /* 108 * Find hash base, and then search the (two-way) linked 109 * list looking for a null_node structure which is referencing 110 * the lower vnode. If found, the increment the null_node 111 * reference count (but NOT the lower vnode's VREF counter). 112 */ 113 hd = NULL_NHASH(lowervp); 114 mtx_lock(&null_hashmtx); 115 LIST_FOREACH(a, hd, null_hash) { 116 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { 117 /* 118 * Since we have the lower node locked the nullfs 119 * node can not be in the process of recycling. If 120 * it had been recycled before we grabed the lower 121 * lock it would not have been found on the hash. 122 */ 123 vp = NULLTOV(a); 124 vref(vp); 125 mtx_unlock(&null_hashmtx); 126 return (vp); 127 } 128 } 129 mtx_unlock(&null_hashmtx); 130 return (NULLVP); 131 } 132 133 /* 134 * Act like null_hashget, but add passed null_node to hash if no existing 135 * node found. 136 */ 137 static struct vnode * 138 null_hashins(mp, xp) 139 struct mount *mp; 140 struct null_node *xp; 141 { 142 struct null_node_hashhead *hd; 143 struct null_node *oxp; 144 struct vnode *ovp; 145 146 hd = NULL_NHASH(xp->null_lowervp); 147 mtx_lock(&null_hashmtx); 148 LIST_FOREACH(oxp, hd, null_hash) { 149 if (oxp->null_lowervp == xp->null_lowervp && 150 NULLTOV(oxp)->v_mount == mp) { 151 /* 152 * See null_hashget for a description of this 153 * operation. 154 */ 155 ovp = NULLTOV(oxp); 156 vref(ovp); 157 mtx_unlock(&null_hashmtx); 158 return (ovp); 159 } 160 } 161 LIST_INSERT_HEAD(hd, xp, null_hash); 162 mtx_unlock(&null_hashmtx); 163 return (NULLVP); 164 } 165 166 static void 167 null_destroy_proto(struct vnode *vp, void *xp) 168 { 169 170 lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL); 171 VI_LOCK(vp); 172 vp->v_data = NULL; 173 vp->v_vnlock = &vp->v_lock; 174 vp->v_op = &dead_vnodeops; 175 VI_UNLOCK(vp); 176 vgone(vp); 177 vput(vp); 178 free(xp, M_NULLFSNODE); 179 } 180 181 static void 182 null_insmntque_dtr(struct vnode *vp, void *xp) 183 { 184 185 vput(((struct null_node *)xp)->null_lowervp); 186 null_destroy_proto(vp, xp); 187 } 188 189 /* 190 * Make a new or get existing nullfs node. 191 * Vp is the alias vnode, lowervp is the lower vnode. 192 * 193 * The lowervp assumed to be locked and having "spare" reference. This routine 194 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers" 195 * the caller's "spare" reference to created nullfs vnode. 196 */ 197 int 198 null_nodeget(mp, lowervp, vpp) 199 struct mount *mp; 200 struct vnode *lowervp; 201 struct vnode **vpp; 202 { 203 struct null_node *xp; 204 struct vnode *vp; 205 int error; 206 207 ASSERT_VOP_LOCKED(lowervp, "lowervp"); 208 KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p", lowervp)); 209 210 /* Lookup the hash firstly. */ 211 *vpp = null_hashget(mp, lowervp); 212 if (*vpp != NULL) { 213 vrele(lowervp); 214 return (0); 215 } 216 217 /* 218 * The insmntque1() call below requires the exclusive lock on 219 * the nullfs vnode. Upgrade the lock now if hash failed to 220 * provide ready to use vnode. 221 */ 222 if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) { 223 KASSERT((MOUNTTONULLMOUNT(mp)->nullm_flags & NULLM_CACHE) != 0, 224 ("lowervp %p is not excl locked and cache is disabled", 225 lowervp)); 226 vn_lock(lowervp, LK_UPGRADE | LK_RETRY); 227 if ((lowervp->v_iflag & VI_DOOMED) != 0) { 228 vput(lowervp); 229 return (ENOENT); 230 } 231 } 232 233 /* 234 * We do not serialize vnode creation, instead we will check for 235 * duplicates later, when adding new vnode to hash. 236 * Note that duplicate can only appear in hash if the lowervp is 237 * locked LK_SHARED. 238 */ 239 xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK); 240 241 error = getnewvnode("null", mp, &null_vnodeops, &vp); 242 if (error) { 243 vput(lowervp); 244 free(xp, M_NULLFSNODE); 245 return (error); 246 } 247 248 xp->null_vnode = vp; 249 xp->null_lowervp = lowervp; 250 xp->null_flags = 0; 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