1 /* $NetBSD: layer_subr.c,v 1.21 2006/12/09 16:11:52 chs 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 1.21 2006/12/09 16:11:52 chs 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 #ifdef LAYERFS_DIAGNOSTIC 88 int layerfs_debug = 1; 89 #endif 90 91 /* 92 * layer cache: 93 * Each cache entry holds a reference to the lower vnode 94 * along with a pointer to the alias vnode. When an 95 * entry is added the lower vnode is VREF'd. When the 96 * alias is removed the lower vnode is vrele'd. 97 */ 98 99 /* 100 * Initialise cache headers 101 */ 102 void 103 layerfs_init() 104 { 105 #ifdef LAYERFS_DIAGNOSTIC 106 if (layerfs_debug) 107 printf("layerfs_init\n"); /* printed during system boot */ 108 #endif 109 } 110 111 /* 112 * Free global resources of layerfs. 113 */ 114 void 115 layerfs_done() 116 { 117 #ifdef LAYERFS_DIAGNOSTIC 118 if (layerfs_debug) 119 printf("layerfs_done\n"); /* printed on layerfs detach */ 120 #endif 121 } 122 123 /* 124 * Return a locked, VREF'ed alias for lower vnode if already exists, else NULL. 125 * The layermp's hashlock must be held on entry. 126 * It will be held upon return iff we return NULL. 127 */ 128 struct vnode * 129 layer_node_find(mp, lowervp) 130 struct mount *mp; 131 struct vnode *lowervp; 132 { 133 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 134 struct layer_node_hashhead *hd; 135 struct layer_node *a; 136 struct vnode *vp; 137 int error; 138 139 /* 140 * Find hash base, and then search the (two-way) linked 141 * list looking for a layer_node structure which is referencing 142 * the lower vnode. If found, the increment the layer_node 143 * reference count (but NOT the lower vnode's VREF counter) 144 * and return the vnode locked. 145 */ 146 hd = LAYER_NHASH(lmp, lowervp); 147 loop: 148 LIST_FOREACH(a, hd, layer_hash) { 149 if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) { 150 vp = LAYERTOV(a); 151 152 /* 153 * We must not let vget() try to lock the layer vp, 154 * since the lower vp is already locked and locking the 155 * layer vp will involve locking the lower vp (whether 156 * or not they actually share a lock). Instead, take 157 * the layer vp's lock separately afterward, but only 158 * if it does not share the lower vp's lock. 159 */ 160 simple_unlock(&lmp->layerm_hashlock); 161 error = vget(vp, 0); 162 if (error) { 163 simple_lock(&lmp->layerm_hashlock); 164 goto loop; 165 } 166 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 167 return (vp); 168 } 169 } 170 return NULL; 171 } 172 173 174 /* 175 * Make a new layer_node node. 176 * Vp is the alias vnode, lowervp is the lower vnode. 177 * Maintain a reference to lowervp. 178 */ 179 int 180 layer_node_alloc(mp, lowervp, vpp) 181 struct mount *mp; 182 struct vnode *lowervp; 183 struct vnode **vpp; 184 { 185 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 186 struct layer_node_hashhead *hd; 187 struct layer_node *xp; 188 struct vnode *vp, *nvp; 189 int error; 190 extern int (**dead_vnodeop_p)(void *); 191 192 if ((error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, 193 &vp)) != 0) 194 return (error); 195 vp->v_type = lowervp->v_type; 196 vp->v_flag |= VLAYER; 197 198 xp = malloc(lmp->layerm_size, M_TEMP, M_WAITOK); 199 if (vp->v_type == VBLK || vp->v_type == VCHR) { 200 MALLOC(vp->v_specinfo, struct specinfo *, 201 sizeof(struct specinfo), M_VNODE, M_WAITOK); 202 vp->v_hashchain = NULL; 203 vp->v_rdev = lowervp->v_rdev; 204 } 205 206 vp->v_data = xp; 207 xp->layer_vnode = vp; 208 xp->layer_lowervp = lowervp; 209 xp->layer_flags = 0; 210 211 /* 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 simple_lock(&lmp->layerm_hashlock); 217 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 218 *vpp = nvp; 219 220 /* free the substructures we've allocated. */ 221 FREE(xp, M_TEMP); 222 if (vp->v_type == VBLK || vp->v_type == VCHR) 223 FREE(vp->v_specinfo, M_VNODE); 224 225 vp->v_type = VBAD; /* node is discarded */ 226 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 227 vrele(vp); /* get rid of it. */ 228 return (0); 229 } 230 231 /* 232 * Now lock the new node. We rely on the fact that we were passed 233 * a locked vnode. If the lower node is exporting a struct lock 234 * (v_vnlock != NULL) then we just set the upper v_vnlock to the 235 * lower one, and both are now locked. If the lower node is exporting 236 * NULL, then we copy that up and manually lock the upper node. 237 * 238 * LAYERFS_UPPERLOCK already has the test, so we use it after copying 239 * up the v_vnlock from below. 240 */ 241 242 vp->v_vnlock = lowervp->v_vnlock; 243 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 244 KASSERT(error == 0); 245 246 /* 247 * Insert the new node into the hash. 248 * Add a reference to the lower node. 249 */ 250 251 *vpp = vp; 252 VREF(lowervp); 253 hd = LAYER_NHASH(lmp, lowervp); 254 LIST_INSERT_HEAD(hd, xp, layer_hash); 255 uvm_vnp_setsize(vp, 0); 256 simple_unlock(&lmp->layerm_hashlock); 257 return (0); 258 } 259 260 261 /* 262 * Try to find an existing layer_node vnode refering 263 * to it, otherwise make a new layer_node vnode which 264 * contains a reference to the lower vnode. 265 * 266 * >>> we assume that the lower node is already locked upon entry, so we 267 * propagate the lock state to upper node << 268 */ 269 int 270 layer_node_create(mp, lowervp, newvpp) 271 struct mount *mp; 272 struct vnode *lowervp; 273 struct vnode **newvpp; 274 { 275 struct vnode *aliasvp; 276 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 277 278 simple_lock(&lmp->layerm_hashlock); 279 aliasvp = layer_node_find(mp, lowervp); 280 if (aliasvp != NULL) { 281 /* 282 * layer_node_find has taken another reference 283 * to the alias vnode and moved the lock holding to 284 * aliasvp 285 */ 286 #ifdef LAYERFS_DIAGNOSTIC 287 if (layerfs_debug) 288 vprint("layer_node_create: exists", aliasvp); 289 #endif 290 } else { 291 int error; 292 293 simple_unlock(&lmp->layerm_hashlock); 294 295 /* 296 * Get new vnode. 297 */ 298 #ifdef LAYERFS_DIAGNOSTIC 299 if (layerfs_debug) 300 printf("layer_node_create: create new alias vnode\n"); 301 #endif 302 303 /* 304 * Make new vnode reference the layer_node. 305 */ 306 if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0) 307 return error; 308 309 /* 310 * aliasvp is already VREF'd by getnewvnode() 311 */ 312 } 313 314 /* 315 * Now that we have VREF'd the upper vnode, release the reference 316 * to the lower node. The existence of the layer_node retains one 317 * reference to the lower node. 318 */ 319 vrele(lowervp); 320 321 #ifdef DIAGNOSTIC 322 if (lowervp->v_usecount < 1) { 323 /* Should never happen... */ 324 vprint("layer_node_create: alias", aliasvp); 325 vprint("layer_node_create: lower", lowervp); 326 panic("layer_node_create: lower has 0 usecount."); 327 } 328 #endif 329 330 #ifdef LAYERFS_DIAGNOSTIC 331 if (layerfs_debug) 332 vprint("layer_node_create: alias", aliasvp); 333 #endif 334 *newvpp = aliasvp; 335 return (0); 336 } 337 338 #ifdef LAYERFS_DIAGNOSTIC 339 struct vnode * 340 layer_checkvp(vp, fil, lno) 341 struct vnode *vp; 342 const char *fil; 343 int lno; 344 { 345 struct layer_node *a = VTOLAYER(vp); 346 #ifdef notyet 347 /* 348 * Can't do this check because vop_reclaim runs 349 * with a funny vop vector. 350 * 351 * WRS - no it doesnt... 352 */ 353 if (vp->v_op != layer_vnodeop_p) { 354 printf ("layer_checkvp: on non-layer-node\n"); 355 #ifdef notyet 356 while (layer_checkvp_barrier) /*WAIT*/ ; 357 #endif 358 panic("layer_checkvp"); 359 }; 360 #endif 361 if (a->layer_lowervp == NULL) { 362 /* Should never happen */ 363 int i; u_long *p; 364 printf("vp = %p, ZERO ptr\n", vp); 365 for (p = (u_long *) a, i = 0; i < 8; i++) 366 printf(" %lx", p[i]); 367 printf("\n"); 368 /* wait for debugger */ 369 panic("layer_checkvp"); 370 } 371 if (a->layer_lowervp->v_usecount < 1) { 372 int i; u_long *p; 373 printf("vp = %p, unref'ed lowervp\n", vp); 374 for (p = (u_long *) a, i = 0; i < 8; i++) 375 printf(" %lx", p[i]); 376 printf("\n"); 377 /* wait for debugger */ 378 panic ("layer with unref'ed lowervp"); 379 }; 380 #ifdef notnow 381 printf("layer %p/%d -> %p/%d [%s, %d]\n", 382 LAYERTOV(a), LAYERTOV(a)->v_usecount, 383 a->layer_lowervp, a->layer_lowervp->v_usecount, 384 fil, lno); 385 #endif 386 return a->layer_lowervp; 387 } 388 #endif 389