1 /* $NetBSD: layer_subr.c,v 1.15 2003/08/07 16:32:36 agc 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 Simulation 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. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp 67 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 68 */ 69 70 #include <sys/cdefs.h> 71 __KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.15 2003/08/07 16:32:36 agc Exp $"); 72 73 #include <sys/param.h> 74 #include <sys/systm.h> 75 #include <sys/proc.h> 76 #include <sys/time.h> 77 #include <sys/vnode.h> 78 #include <sys/mount.h> 79 #include <sys/namei.h> 80 #include <sys/malloc.h> 81 #include <miscfs/specfs/specdev.h> 82 #include <miscfs/genfs/layer.h> 83 #include <miscfs/genfs/layer_extern.h> 84 85 #define NLAYERNODECACHE 16 86 87 /* 88 * layer cache: 89 * Each cache entry holds a reference to the lower vnode 90 * along with a pointer to the alias vnode. When an 91 * entry is added the lower vnode is VREF'd. When the 92 * alias is removed the lower vnode is vrele'd. 93 */ 94 95 /* 96 * Initialise cache headers 97 */ 98 void 99 layerfs_init() 100 { 101 #ifdef LAYERFS_DIAGNOSTIC 102 printf("layerfs_init\n"); /* printed during system boot */ 103 #endif 104 } 105 106 /* 107 * Free global resources of layerfs. 108 */ 109 void 110 layerfs_done() 111 { 112 #ifdef LAYERFS_DIAGNOSTIC 113 printf("layerfs_done\n"); /* printed on layerfs detach */ 114 #endif 115 } 116 117 /* 118 * Return a locked, VREF'ed alias for lower vnode if already exists, else 0. 119 */ 120 struct vnode * 121 layer_node_find(mp, lowervp) 122 struct mount *mp; 123 struct vnode *lowervp; 124 { 125 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 126 struct layer_node_hashhead *hd; 127 struct layer_node *a; 128 struct vnode *vp; 129 130 /* 131 * Find hash base, and then search the (two-way) linked 132 * list looking for a layer_node structure which is referencing 133 * the lower vnode. If found, the increment the layer_node 134 * reference count (but NOT the lower vnode's VREF counter) 135 * and return the vnode locked. 136 */ 137 hd = LAYER_NHASH(lmp, lowervp); 138 loop: 139 simple_lock(&lmp->layerm_hashlock); 140 for (a = hd->lh_first; a != 0; a = a->layer_hash.le_next) { 141 if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) { 142 vp = LAYERTOV(a); 143 simple_unlock(&lmp->layerm_hashlock); 144 /* 145 * We must be careful here as the fact the lower 146 * vnode is locked will imply vp is locked unless 147 * someone has decided to start vclean'ing either 148 * vp or lowervp. 149 * 150 * So we try for an exclusive, recursive lock 151 * on the upper vnode. If it fails, vcleaning 152 * is in progress (so when we try again, we'll 153 * fail). If it succeeds, we now have double 154 * locked the bottom node. So we do an explicit 155 * VOP_UNLOCK on it to keep the counts right. Note 156 * that we will end up with the upper node and 157 * the lower node locked once. 158 */ 159 if (vget(vp, LK_EXCLUSIVE | LK_CANRECURSE)) { 160 printf ("layer_node_find: vget failed.\n"); 161 goto loop; 162 }; 163 VOP_UNLOCK(lowervp, 0); 164 return (vp); 165 } 166 } 167 168 simple_unlock(&lmp->layerm_hashlock); 169 return NULL; 170 } 171 172 173 /* 174 * Make a new layer_node node. 175 * Vp is the alias vnode, lowervp is the lower vnode. 176 * Maintain a reference to lowervp. 177 */ 178 int 179 layer_node_alloc(mp, lowervp, vpp) 180 struct mount *mp; 181 struct vnode *lowervp; 182 struct vnode **vpp; 183 { 184 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 185 struct layer_node_hashhead *hd; 186 struct layer_node *xp; 187 struct vnode *vp, *nvp; 188 int error; 189 extern int (**dead_vnodeop_p) __P((void *)); 190 191 if ((error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, 192 &vp)) != 0) 193 return (error); 194 vp->v_type = lowervp->v_type; 195 vp->v_flag |= VLAYER; 196 197 xp = malloc(lmp->layerm_size, M_TEMP, M_WAITOK); 198 if (vp->v_type == VBLK || vp->v_type == VCHR) { 199 MALLOC(vp->v_specinfo, struct specinfo *, 200 sizeof(struct specinfo), M_VNODE, M_WAITOK); 201 vp->v_hashchain = NULL; 202 vp->v_rdev = lowervp->v_rdev; 203 } 204 205 vp->v_data = xp; 206 xp->layer_vnode = vp; 207 xp->layer_lowervp = lowervp; 208 xp->layer_flags = 0; 209 /* 210 * Before we insert our new node onto the hash chains, 211 * check to see if someone else has beaten us to it. 212 * (We could have slept in MALLOC.) 213 */ 214 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 215 *vpp = nvp; 216 217 /* free the substructures we've allocated. */ 218 FREE(xp, M_TEMP); 219 if (vp->v_type == VBLK || vp->v_type == VCHR) 220 FREE(vp->v_specinfo, M_VNODE); 221 222 vp->v_type = VBAD; /* node is discarded */ 223 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 224 vrele(vp); /* get rid of it. */ 225 return (0); 226 } 227 228 simple_lock(&lmp->layerm_hashlock); 229 230 /* 231 * Now lock the new node. We rely on the fact that we were passed 232 * a locked vnode. If the lower node is exporting a struct lock 233 * (v_vnlock != NULL) then we just set the upper v_vnlock to the 234 * lower one, and both are now locked. If the lower node is exporting 235 * NULL, then we copy that up and manually lock the upper node. 236 * 237 * LAYERFS_UPPERLOCK already has the test, so we use it after copying 238 * up the v_vnlock from below. 239 */ 240 241 vp->v_vnlock = lowervp->v_vnlock; 242 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 243 244 if (error) { 245 /* 246 * How did we get a locking error? The node just came off 247 * of the free list, and we're the only routine which 248 * knows it's there... 249 */ 250 vp->v_vnlock = &vp->v_lock; 251 *vpp = NULL; 252 253 /* free the substructures we've allocated. */ 254 FREE(xp, M_TEMP); 255 if (vp->v_type == VBLK || vp->v_type == VCHR) 256 FREE(vp->v_specinfo, M_VNODE); 257 258 vp->v_type = VBAD; /* node is discarded */ 259 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 260 vrele(vp); /* get rid of it. */ 261 return (error); 262 } 263 /* 264 * NetBSD used to do an inlined checkalias here. We do not, as 265 * we never flag device nodes as being aliased. The lowervp 266 * node will, when appropriate, be flaged as an alias. 267 */ 268 269 *vpp = vp; 270 VREF(lowervp); /* Take into account reference held in layer_node */ 271 hd = LAYER_NHASH(lmp, lowervp); 272 LIST_INSERT_HEAD(hd, xp, layer_hash); 273 uvm_vnp_setsize(vp, 0); 274 simple_unlock(&lmp->layerm_hashlock); 275 return (0); 276 } 277 278 279 /* 280 * Try to find an existing layer_node vnode refering 281 * to it, otherwise make a new layer_node vnode which 282 * contains a reference to the lower vnode. 283 * 284 * >>> we assume that the lower node is already locked upon entry, so we 285 * propagate the lock state to upper node << 286 */ 287 int 288 layer_node_create(mp, lowervp, newvpp) 289 struct mount *mp; 290 struct vnode *lowervp; 291 struct vnode **newvpp; 292 { 293 struct vnode *aliasvp; 294 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 295 296 if ((aliasvp = layer_node_find(mp, lowervp)) != NULL) { 297 /* 298 * layer_node_find has taken another reference 299 * to the alias vnode and moved the lock holding to 300 * aliasvp 301 */ 302 #ifdef LAYERFS_DIAGNOSTIC 303 vprint("layer_node_create: exists", aliasvp); 304 #endif 305 } else { 306 int error; 307 308 /* 309 * Get new vnode. 310 */ 311 #ifdef LAYERFS_DIAGNOSTIC 312 printf("layer_node_create: create new alias vnode\n"); 313 #endif 314 315 /* 316 * Make new vnode reference the layer_node. 317 */ 318 if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0) 319 return error; 320 321 /* 322 * aliasvp is already VREF'd by getnewvnode() 323 */ 324 } 325 326 /* 327 * Now that we have VREF'd the upper vnode, release the reference 328 * to the lower node. The existance of the layer_node retains one 329 * reference to the lower node. 330 */ 331 vrele(lowervp); 332 333 #ifdef DIAGNOSTIC 334 if (lowervp->v_usecount < 1) { 335 /* Should never happen... */ 336 vprint("layer_node_create: alias", aliasvp); 337 vprint("layer_node_create: lower", lowervp); 338 panic("layer_node_create: lower has 0 usecount."); 339 }; 340 #endif 341 342 #ifdef LAYERFS_DIAGNOSTIC 343 vprint("layer_node_create: alias", aliasvp); 344 #endif 345 *newvpp = aliasvp; 346 return (0); 347 } 348 349 struct vnode * 350 layer_checkvp(vp, fil, lno) 351 struct vnode *vp; 352 char *fil; 353 int lno; 354 { 355 struct layer_node *a = VTOLAYER(vp); 356 #ifdef notyet 357 /* 358 * Can't do this check because vop_reclaim runs 359 * with a funny vop vector. 360 * 361 * WRS - no it doesnt... 362 */ 363 if (vp->v_op != layer_vnodeop_p) { 364 printf ("layer_checkvp: on non-layer-node\n"); 365 #ifdef notyet 366 while (layer_checkvp_barrier) /*WAIT*/ ; 367 #endif 368 panic("layer_checkvp"); 369 }; 370 #endif 371 if (a->layer_lowervp == NULL) { 372 /* Should never happen */ 373 int i; u_long *p; 374 printf("vp = %p, ZERO ptr\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_checkvp"); 380 } 381 if (a->layer_lowervp->v_usecount < 1) { 382 int i; u_long *p; 383 printf("vp = %p, unref'ed lowervp\n", vp); 384 for (p = (u_long *) a, i = 0; i < 8; i++) 385 printf(" %lx", p[i]); 386 printf("\n"); 387 /* wait for debugger */ 388 panic ("layer with unref'ed lowervp"); 389 }; 390 #ifdef notnow 391 printf("layer %p/%d -> %p/%d [%s, %d]\n", 392 LAYERTOV(a), LAYERTOV(a)->v_usecount, 393 a->layer_lowervp, a->layer_lowervp->v_usecount, 394 fil, lno); 395 #endif 396 return a->layer_lowervp; 397 } 398