1 /* $NetBSD: layer_subr.c,v 1.4 1999/10/25 23:34:31 wrstuden Exp $ */ 2 3 /* 4 * Copyright (c) 1999 National Aeronautics & Space Administration 5 * All rights reserved. 6 * 7 * This software was written by William Studenmund of the 8 * Numerical Aerospace Similation Facility, NASA Ames Research Center. 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 the name of the National Aeronautics & Space Administration 19 * nor the names of its contributors may be used to endorse or promote 20 * products derived from this software without specific prior written 21 * permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE NATIONAL AERONAUTICS & SPACE ADMINISTRATION 24 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 25 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 26 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE ADMINISTRATION OR CONTRIB- 27 * UTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, 28 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 29 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 30 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 31 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 32 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 * POSSIBILITY OF SUCH DAMAGE. 34 */ 35 /* 36 * Copyright (c) 1992, 1993 37 * The Regents of the University of California. All rights reserved. 38 * 39 * This code is derived from software donated to Berkeley by 40 * Jan-Simon Pendry. 41 * 42 * Redistribution and use in source and binary forms, with or without 43 * modification, are permitted provided that the following conditions 44 * are met: 45 * 1. Redistributions of source code must retain the above copyright 46 * notice, this list of conditions and the following disclaimer. 47 * 2. Redistributions in binary form must reproduce the above copyright 48 * notice, this list of conditions and the following disclaimer in the 49 * documentation and/or other materials provided with the distribution. 50 * 3. All advertising materials mentioning features or use of this software 51 * must display the following acknowledgement: 52 * This product includes software developed by the University of 53 * California, Berkeley and its contributors. 54 * 4. Neither the name of the University nor the names of its contributors 55 * may be used to endorse or promote products derived from this software 56 * without specific prior written permission. 57 * 58 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 59 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 60 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 61 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 62 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 63 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 64 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 65 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 66 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 67 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 68 * SUCH DAMAGE. 69 * 70 * from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp 71 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 72 */ 73 74 #include <sys/param.h> 75 #include <sys/systm.h> 76 #include <sys/proc.h> 77 #include <sys/time.h> 78 #include <sys/types.h> 79 #include <sys/vnode.h> 80 #include <sys/mount.h> 81 #include <sys/namei.h> 82 #include <sys/malloc.h> 83 #include <miscfs/specfs/specdev.h> 84 #include <miscfs/genfs/layer.h> 85 #include <miscfs/genfs/layer_extern.h> 86 87 #define NLAYERNODECACHE 16 88 89 /* 90 * layer cache: 91 * Each cache entry holds a reference to the lower vnode 92 * along with a pointer to the alias vnode. When an 93 * entry is added the lower vnode is VREF'd. When the 94 * alias is removed the lower vnode is vrele'd. 95 */ 96 97 /* 98 * Initialise cache headers 99 */ 100 void 101 layerfs_init() 102 { 103 104 #ifdef LAYERFS_DIAGNOSTIC 105 printf("layerfs_init\n"); /* printed during system boot */ 106 #endif 107 } 108 109 /* 110 * Return a locked, VREF'ed alias for lower vnode if already exists, else 0. 111 */ 112 struct vnode * 113 layer_node_find(mp, lowervp) 114 struct mount *mp; 115 struct vnode *lowervp; 116 { 117 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 118 struct layer_node_hashhead *hd; 119 struct layer_node *a; 120 struct vnode *vp; 121 122 /* 123 * Find hash base, and then search the (two-way) linked 124 * list looking for a layer_node structure which is referencing 125 * the lower vnode. If found, the increment the layer_node 126 * reference count (but NOT the lower vnode's VREF counter) 127 * and return the vnode locked. 128 */ 129 hd = LAYER_NHASH(lmp, lowervp); 130 loop: 131 simple_lock(&lmp->layerm_hashlock); 132 for (a = hd->lh_first; a != 0; a = a->layer_hash.le_next) { 133 if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) { 134 vp = LAYERTOV(a); 135 simple_unlock(&lmp->layerm_hashlock); 136 /* 137 * We must be careful here as the fact the lower 138 * vnode is locked will imply vp is locked unless 139 * someone has decided to start vclean'ing either 140 * vp or lowervp. 141 * 142 * So we try for an exclusive, recursive lock 143 * on the upper vnode. If it fails, vcleaning 144 * is in progress (so when we try again, we'll 145 * fail). If it succeeds, we now have double 146 * locked the bottom node. So we do an explicit 147 * VOP_UNLOCK on it to keep the counts right. Note 148 * that we will end up with the upper node and 149 * the lower node locked once. 150 */ 151 if (vget(vp, LK_EXCLUSIVE | LK_CANRECURSE)) { 152 printf ("layer_node_find: vget failed.\n"); 153 goto loop; 154 }; 155 VOP_UNLOCK(lowervp, 0); 156 return (vp); 157 } 158 } 159 160 simple_unlock(&lmp->layerm_hashlock); 161 return NULL; 162 } 163 164 165 /* 166 * Make a new layer_node node. 167 * Vp is the alias vnode, lowervp is the lower vnode. 168 * Maintain a reference to lowervp. 169 */ 170 int 171 layer_node_alloc(mp, lowervp, vpp) 172 struct mount *mp; 173 struct vnode *lowervp; 174 struct vnode **vpp; 175 { 176 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 177 struct layer_node_hashhead *hd; 178 struct layer_node *xp; 179 struct vnode *vp, *nvp; 180 int error; 181 extern int (**dead_vnodeop_p) __P((void *)); 182 183 if ((error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, 184 &vp)) != 0) 185 return (error); 186 vp->v_type = lowervp->v_type; 187 vp->v_flag |= VLAYER; 188 189 MALLOC(xp, struct layer_node *, lmp->layerm_size, M_TEMP, M_WAITOK); 190 if (vp->v_type == VBLK || vp->v_type == VCHR) { 191 MALLOC(vp->v_specinfo, struct specinfo *, 192 sizeof(struct specinfo), M_VNODE, M_WAITOK); 193 vp->v_hashchain = NULL; 194 vp->v_rdev = lowervp->v_rdev; 195 } 196 197 vp->v_data = xp; 198 xp->layer_vnode = vp; 199 xp->layer_lowervp = lowervp; 200 xp->layer_flags = 0; 201 /* 202 * Before we insert our new node onto the hash chains, 203 * check to see if someone else has beaten us to it. 204 * (We could have slept in MALLOC.) 205 */ 206 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 207 *vpp = nvp; 208 209 /* free the substructures we've allocated. */ 210 FREE(xp, M_TEMP); 211 if (vp->v_type == VBLK || vp->v_type == VCHR) 212 FREE(vp->v_specinfo, M_VNODE); 213 214 vp->v_type = VBAD; /* node is discarded */ 215 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 216 vrele(vp); /* get rid of it. */ 217 return (0); 218 } 219 220 simple_lock(&lmp->layerm_hashlock); 221 222 /* 223 * Now lock the new node. We rely on the fact that we were passed 224 * a locked vnode. If the lower node is exporting a struct lock 225 * (v_vnlock != NULL) then we just set the upper v_vnlock to the 226 * lower one, and both are now locked. If the lower node is exporting 227 * NULL, then we copy that up and manually lock the upper node. 228 * 229 * LAYERFS_UPPERLOCK already has the test, so we use it after copying 230 * up the v_vnlock from below. 231 */ 232 233 vp->v_vnlock = lowervp->v_vnlock; 234 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 235 236 if (error) { 237 /* 238 * How did we get a locking error? The node just came off 239 * of the free list, and we're the only routine which 240 * knows it's there... 241 */ 242 vp->v_vnlock = &vp->v_lock; 243 *vpp = NULL; 244 245 /* free the substructures we've allocated. */ 246 FREE(xp, M_TEMP); 247 if (vp->v_type == VBLK || vp->v_type == VCHR) 248 FREE(vp->v_specinfo, M_VNODE); 249 250 vp->v_type = VBAD; /* node is discarded */ 251 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 252 vrele(vp); /* get rid of it. */ 253 return (error); 254 } 255 /* 256 * NetBSD used to do an inlined checkalias here. We do not, as 257 * we never flag device nodes as being aliased. The lowervp 258 * node will, when appropriate, be flaged as an alias. 259 */ 260 261 *vpp = vp; 262 VREF(lowervp); /* Take into account reference held in layer_node */ 263 hd = LAYER_NHASH(lmp, lowervp); 264 LIST_INSERT_HEAD(hd, xp, layer_hash); 265 simple_unlock(&lmp->layerm_hashlock); 266 return (0); 267 } 268 269 270 /* 271 * Try to find an existing layer_node vnode refering 272 * to it, otherwise make a new layer_node vnode which 273 * contains a reference to the lower vnode. 274 * 275 * >>> we assume that the lower node is already locked upon entry, so we 276 * propagate the lock state to upper node << 277 */ 278 int 279 layer_node_create(mp, lowervp, newvpp) 280 struct mount *mp; 281 struct vnode *lowervp; 282 struct vnode **newvpp; 283 { 284 struct vnode *aliasvp; 285 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 286 287 if ((aliasvp = layer_node_find(mp, lowervp)) != NULL) { 288 /* 289 * layer_node_find has taken another reference 290 * to the alias vnode and moved the lock holding to 291 * aliasvp 292 */ 293 #ifdef LAYERFS_DIAGNOSTIC 294 vprint("layer_node_create: exists", aliasvp); 295 #endif 296 } else { 297 int error; 298 299 /* 300 * Get new vnode. 301 */ 302 #ifdef LAYERFS_DIAGNOSTIC 303 printf("layer_node_create: create new alias vnode\n"); 304 #endif 305 306 /* 307 * Make new vnode reference the layer_node. 308 */ 309 if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0) 310 return error; 311 312 /* 313 * aliasvp is already VREF'd by getnewvnode() 314 */ 315 } 316 317 /* 318 * Now that we have VREF'd the upper vnode, release the reference 319 * to the lower node. The existance of the layer_node retains one 320 * reference to the lower node. 321 */ 322 vrele(lowervp); 323 324 #ifdef DIAGNOSTIC 325 if (lowervp->v_usecount < 1) { 326 /* Should never happen... */ 327 vprint("layer_node_create: alias", aliasvp); 328 vprint("layer_node_create: lower", lowervp); 329 panic("layer_node_create: lower has 0 usecount."); 330 }; 331 #endif 332 333 #ifdef LAYERFS_DIAGNOSTIC 334 vprint("layer_node_create: alias", aliasvp); 335 #endif 336 *newvpp = aliasvp; 337 return (0); 338 } 339 340 struct vnode * 341 layer_checkvp(vp, fil, lno) 342 struct vnode *vp; 343 char *fil; 344 int lno; 345 { 346 struct layer_node *a = VTOLAYER(vp); 347 #ifdef notyet 348 /* 349 * Can't do this check because vop_reclaim runs 350 * with a funny vop vector. 351 * 352 * WRS - no it doesnt... 353 */ 354 if (vp->v_op != layer_vnodeop_p) { 355 printf ("layer_checkvp: on non-layer-node\n"); 356 #ifdef notyet 357 while (layer_checkvp_barrier) /*WAIT*/ ; 358 #endif 359 panic("layer_checkvp"); 360 }; 361 #endif 362 if (a->layer_lowervp == NULL) { 363 /* Should never happen */ 364 int i; u_long *p; 365 printf("vp = %p, ZERO ptr\n", vp); 366 for (p = (u_long *) a, i = 0; i < 8; i++) 367 printf(" %lx", p[i]); 368 printf("\n"); 369 /* wait for debugger */ 370 panic("layer_checkvp"); 371 } 372 if (a->layer_lowervp->v_usecount < 1) { 373 int i; u_long *p; 374 printf("vp = %p, unref'ed lowervp\n", vp); 375 for (p = (u_long *) a, i = 0; i < 8; i++) 376 printf(" %lx", p[i]); 377 printf("\n"); 378 /* wait for debugger */ 379 panic ("layer with unref'ed lowervp"); 380 }; 381 #ifdef notnow 382 printf("layer %p/%d -> %p/%d [%s, %d]\n", 383 LAYERTOV(a), LAYERTOV(a)->v_usecount, 384 a->layer_lowervp, a->layer_lowervp->v_usecount, 385 fil, lno); 386 #endif 387 return a->layer_lowervp; 388 } 389