1 /* $NetBSD: layer_subr.c,v 1.6 2000/03/16 18:08:24 jdolecek 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 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 #ifdef LAYERFS_DIAGNOSTIC 104 printf("layerfs_init\n"); /* printed during system boot */ 105 #endif 106 } 107 108 /* 109 * Free global resources of layerfs. 110 */ 111 void 112 layerfs_done() 113 { 114 #ifdef LAYERFS_DIAGNOSTIC 115 printf("layerfs_done\n"); /* printed on layerfs detach */ 116 #endif 117 } 118 119 /* 120 * Return a locked, VREF'ed alias for lower vnode if already exists, else 0. 121 */ 122 struct vnode * 123 layer_node_find(mp, lowervp) 124 struct mount *mp; 125 struct vnode *lowervp; 126 { 127 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 128 struct layer_node_hashhead *hd; 129 struct layer_node *a; 130 struct vnode *vp; 131 132 /* 133 * Find hash base, and then search the (two-way) linked 134 * list looking for a layer_node structure which is referencing 135 * the lower vnode. If found, the increment the layer_node 136 * reference count (but NOT the lower vnode's VREF counter) 137 * and return the vnode locked. 138 */ 139 hd = LAYER_NHASH(lmp, lowervp); 140 loop: 141 simple_lock(&lmp->layerm_hashlock); 142 for (a = hd->lh_first; a != 0; a = a->layer_hash.le_next) { 143 if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) { 144 vp = LAYERTOV(a); 145 simple_unlock(&lmp->layerm_hashlock); 146 /* 147 * We must be careful here as the fact the lower 148 * vnode is locked will imply vp is locked unless 149 * someone has decided to start vclean'ing either 150 * vp or lowervp. 151 * 152 * So we try for an exclusive, recursive lock 153 * on the upper vnode. If it fails, vcleaning 154 * is in progress (so when we try again, we'll 155 * fail). If it succeeds, we now have double 156 * locked the bottom node. So we do an explicit 157 * VOP_UNLOCK on it to keep the counts right. Note 158 * that we will end up with the upper node and 159 * the lower node locked once. 160 */ 161 if (vget(vp, LK_EXCLUSIVE | LK_CANRECURSE)) { 162 printf ("layer_node_find: vget failed.\n"); 163 goto loop; 164 }; 165 VOP_UNLOCK(lowervp, 0); 166 return (vp); 167 } 168 } 169 170 simple_unlock(&lmp->layerm_hashlock); 171 return NULL; 172 } 173 174 175 /* 176 * Make a new layer_node node. 177 * Vp is the alias vnode, lowervp is the lower vnode. 178 * Maintain a reference to lowervp. 179 */ 180 int 181 layer_node_alloc(mp, lowervp, vpp) 182 struct mount *mp; 183 struct vnode *lowervp; 184 struct vnode **vpp; 185 { 186 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 187 struct layer_node_hashhead *hd; 188 struct layer_node *xp; 189 struct vnode *vp, *nvp; 190 int error; 191 extern int (**dead_vnodeop_p) __P((void *)); 192 193 if ((error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, 194 &vp)) != 0) 195 return (error); 196 vp->v_type = lowervp->v_type; 197 vp->v_flag |= VLAYER; 198 199 MALLOC(xp, struct layer_node *, lmp->layerm_size, M_TEMP, M_WAITOK); 200 if (vp->v_type == VBLK || vp->v_type == VCHR) { 201 MALLOC(vp->v_specinfo, struct specinfo *, 202 sizeof(struct specinfo), M_VNODE, M_WAITOK); 203 vp->v_hashchain = NULL; 204 vp->v_rdev = lowervp->v_rdev; 205 } 206 207 vp->v_data = xp; 208 xp->layer_vnode = vp; 209 xp->layer_lowervp = lowervp; 210 xp->layer_flags = 0; 211 /* 212 * Before we insert our new node onto the hash chains, 213 * check to see if someone else has beaten us to it. 214 * (We could have slept in MALLOC.) 215 */ 216 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 217 *vpp = nvp; 218 219 /* free the substructures we've allocated. */ 220 FREE(xp, M_TEMP); 221 if (vp->v_type == VBLK || vp->v_type == VCHR) 222 FREE(vp->v_specinfo, M_VNODE); 223 224 vp->v_type = VBAD; /* node is discarded */ 225 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 226 vrele(vp); /* get rid of it. */ 227 return (0); 228 } 229 230 simple_lock(&lmp->layerm_hashlock); 231 232 /* 233 * Now lock the new node. We rely on the fact that we were passed 234 * a locked vnode. If the lower node is exporting a struct lock 235 * (v_vnlock != NULL) then we just set the upper v_vnlock to the 236 * lower one, and both are now locked. If the lower node is exporting 237 * NULL, then we copy that up and manually lock the upper node. 238 * 239 * LAYERFS_UPPERLOCK already has the test, so we use it after copying 240 * up the v_vnlock from below. 241 */ 242 243 vp->v_vnlock = lowervp->v_vnlock; 244 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 245 246 if (error) { 247 /* 248 * How did we get a locking error? The node just came off 249 * of the free list, and we're the only routine which 250 * knows it's there... 251 */ 252 vp->v_vnlock = &vp->v_lock; 253 *vpp = NULL; 254 255 /* free the substructures we've allocated. */ 256 FREE(xp, M_TEMP); 257 if (vp->v_type == VBLK || vp->v_type == VCHR) 258 FREE(vp->v_specinfo, M_VNODE); 259 260 vp->v_type = VBAD; /* node is discarded */ 261 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 262 vrele(vp); /* get rid of it. */ 263 return (error); 264 } 265 /* 266 * NetBSD used to do an inlined checkalias here. We do not, as 267 * we never flag device nodes as being aliased. The lowervp 268 * node will, when appropriate, be flaged as an alias. 269 */ 270 271 *vpp = vp; 272 VREF(lowervp); /* Take into account reference held in layer_node */ 273 hd = LAYER_NHASH(lmp, lowervp); 274 LIST_INSERT_HEAD(hd, xp, layer_hash); 275 simple_unlock(&lmp->layerm_hashlock); 276 return (0); 277 } 278 279 280 /* 281 * Try to find an existing layer_node vnode refering 282 * to it, otherwise make a new layer_node vnode which 283 * contains a reference to the lower vnode. 284 * 285 * >>> we assume that the lower node is already locked upon entry, so we 286 * propagate the lock state to upper node << 287 */ 288 int 289 layer_node_create(mp, lowervp, newvpp) 290 struct mount *mp; 291 struct vnode *lowervp; 292 struct vnode **newvpp; 293 { 294 struct vnode *aliasvp; 295 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 296 297 if ((aliasvp = layer_node_find(mp, lowervp)) != NULL) { 298 /* 299 * layer_node_find has taken another reference 300 * to the alias vnode and moved the lock holding to 301 * aliasvp 302 */ 303 #ifdef LAYERFS_DIAGNOSTIC 304 vprint("layer_node_create: exists", aliasvp); 305 #endif 306 } else { 307 int error; 308 309 /* 310 * Get new vnode. 311 */ 312 #ifdef LAYERFS_DIAGNOSTIC 313 printf("layer_node_create: create new alias vnode\n"); 314 #endif 315 316 /* 317 * Make new vnode reference the layer_node. 318 */ 319 if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0) 320 return error; 321 322 /* 323 * aliasvp is already VREF'd by getnewvnode() 324 */ 325 } 326 327 /* 328 * Now that we have VREF'd the upper vnode, release the reference 329 * to the lower node. The existance of the layer_node retains one 330 * reference to the lower node. 331 */ 332 vrele(lowervp); 333 334 #ifdef DIAGNOSTIC 335 if (lowervp->v_usecount < 1) { 336 /* Should never happen... */ 337 vprint("layer_node_create: alias", aliasvp); 338 vprint("layer_node_create: lower", lowervp); 339 panic("layer_node_create: lower has 0 usecount."); 340 }; 341 #endif 342 343 #ifdef LAYERFS_DIAGNOSTIC 344 vprint("layer_node_create: alias", aliasvp); 345 #endif 346 *newvpp = aliasvp; 347 return (0); 348 } 349 350 struct vnode * 351 layer_checkvp(vp, fil, lno) 352 struct vnode *vp; 353 char *fil; 354 int lno; 355 { 356 struct layer_node *a = VTOLAYER(vp); 357 #ifdef notyet 358 /* 359 * Can't do this check because vop_reclaim runs 360 * with a funny vop vector. 361 * 362 * WRS - no it doesnt... 363 */ 364 if (vp->v_op != layer_vnodeop_p) { 365 printf ("layer_checkvp: on non-layer-node\n"); 366 #ifdef notyet 367 while (layer_checkvp_barrier) /*WAIT*/ ; 368 #endif 369 panic("layer_checkvp"); 370 }; 371 #endif 372 if (a->layer_lowervp == NULL) { 373 /* Should never happen */ 374 int i; u_long *p; 375 printf("vp = %p, ZERO ptr\n", vp); 376 for (p = (u_long *) a, i = 0; i < 8; i++) 377 printf(" %lx", p[i]); 378 printf("\n"); 379 /* wait for debugger */ 380 panic("layer_checkvp"); 381 } 382 if (a->layer_lowervp->v_usecount < 1) { 383 int i; u_long *p; 384 printf("vp = %p, unref'ed lowervp\n", vp); 385 for (p = (u_long *) a, i = 0; i < 8; i++) 386 printf(" %lx", p[i]); 387 printf("\n"); 388 /* wait for debugger */ 389 panic ("layer with unref'ed lowervp"); 390 }; 391 #ifdef notnow 392 printf("layer %p/%d -> %p/%d [%s, %d]\n", 393 LAYERTOV(a), LAYERTOV(a)->v_usecount, 394 a->layer_lowervp, a->layer_lowervp->v_usecount, 395 fil, lno); 396 #endif 397 return a->layer_lowervp; 398 } 399