layer_subr.c revision 1.22.6.2
1 /* $NetBSD: layer_subr.c,v 1.22.6.2 2007/12/06 21:03:38 ad 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 1.22.6.2 2007/12/06 21:03:38 ad 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/kmem.h> 81 #include <sys/malloc.h> 82 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 #ifdef LAYERFS_DIAGNOSTIC 90 int layerfs_debug = 1; 91 #endif 92 93 /* 94 * layer cache: 95 * Each cache entry holds a reference to the lower vnode 96 * along with a pointer to the alias vnode. When an 97 * entry is added the lower vnode is VREF'd. When the 98 * alias is removed the lower vnode is vrele'd. 99 */ 100 101 /* 102 * Initialise cache headers 103 */ 104 void 105 layerfs_init() 106 { 107 #ifdef LAYERFS_DIAGNOSTIC 108 if (layerfs_debug) 109 printf("layerfs_init\n"); /* printed during system boot */ 110 #endif 111 } 112 113 /* 114 * Free global resources of layerfs. 115 */ 116 void 117 layerfs_done() 118 { 119 #ifdef LAYERFS_DIAGNOSTIC 120 if (layerfs_debug) 121 printf("layerfs_done\n"); /* printed on layerfs detach */ 122 #endif 123 } 124 125 /* 126 * Return a locked, VREF'ed alias for lower vnode if already exists, else NULL. 127 * The layermp's hashlock must be held on entry. 128 * It will be held upon return iff we return NULL. 129 */ 130 struct vnode * 131 layer_node_find(mp, lowervp) 132 struct mount *mp; 133 struct vnode *lowervp; 134 { 135 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 136 struct layer_node_hashhead *hd; 137 struct layer_node *a; 138 struct vnode *vp; 139 int error; 140 141 /* 142 * Find hash base, and then search the (two-way) linked 143 * list looking for a layer_node structure which is referencing 144 * the lower vnode. If found, the increment the layer_node 145 * reference count (but NOT the lower vnode's VREF counter) 146 * and return the vnode locked. 147 */ 148 hd = LAYER_NHASH(lmp, lowervp); 149 loop: 150 LIST_FOREACH(a, hd, layer_hash) { 151 if (a->layer_lowervp == lowervp && LAYERTOV(a)->v_mount == mp) { 152 vp = LAYERTOV(a); 153 154 /* 155 * We must not let vget() try to lock the layer vp, 156 * since the lower vp is already locked and locking the 157 * layer vp will involve locking the lower vp (whether 158 * or not they actually share a lock). Instead, take 159 * the layer vp's lock separately afterward, but only 160 * if it does not share the lower vp's lock. 161 */ 162 mutex_enter(&vp->v_interlock); 163 mutex_exit(&lmp->layerm_hashlock); 164 error = vget(vp, LK_INTERLOCK); 165 if (error) { 166 mutex_enter(&lmp->layerm_hashlock); 167 goto loop; 168 } 169 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 170 return (vp); 171 } 172 } 173 return NULL; 174 } 175 176 177 /* 178 * Make a new layer_node node. 179 * Vp is the alias vnode, lowervp is the lower vnode. 180 * Maintain a reference to lowervp. 181 */ 182 int 183 layer_node_alloc(mp, lowervp, vpp) 184 struct mount *mp; 185 struct vnode *lowervp; 186 struct vnode **vpp; 187 { 188 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 189 struct layer_node_hashhead *hd; 190 struct layer_node *xp; 191 struct vnode *vp, *nvp; 192 int error; 193 extern int (**dead_vnodeop_p)(void *); 194 195 error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp); 196 if (error != 0) 197 return (error); 198 vp->v_type = lowervp->v_type; 199 mutex_enter(&vp->v_interlock); 200 vp->v_iflag |= VI_LAYER; 201 mutex_exit(&vp->v_interlock); 202 203 xp = kmem_alloc(lmp->layerm_size, KM_SLEEP); 204 if (xp == NULL) { 205 ungetnewvnode(vp); 206 return ENOMEM; 207 } 208 if (vp->v_type == VBLK || vp->v_type == VCHR) { 209 MALLOC(vp->v_specinfo, struct specinfo *, 210 sizeof(struct specinfo), M_VNODE, M_WAITOK); 211 vp->v_hashchain = NULL; 212 vp->v_rdev = lowervp->v_rdev; 213 } 214 215 vp->v_data = xp; 216 xp->layer_vnode = vp; 217 xp->layer_lowervp = lowervp; 218 xp->layer_flags = 0; 219 220 /* 221 * Before we insert our new node onto the hash chains, 222 * check to see if someone else has beaten us to it. 223 * (We could have slept in MALLOC.) 224 */ 225 mutex_enter(&lmp->layerm_hashlock); 226 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 227 *vpp = nvp; 228 229 /* free the substructures we've allocated. */ 230 kmem_free(xp, lmp->layerm_size); 231 if (vp->v_type == VBLK || vp->v_type == VCHR) 232 FREE(vp->v_specinfo, M_VNODE); 233 234 vp->v_type = VBAD; /* node is discarded */ 235 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 236 vrele(vp); /* get rid of it. */ 237 return (0); 238 } 239 240 /* 241 * Now lock the new node. We rely on the fact that we were passed 242 * a locked vnode. If the lower node is exporting a struct lock 243 * (v_vnlock != NULL) then we just set the upper v_vnlock to the 244 * lower one, and both are now locked. If the lower node is exporting 245 * NULL, then we copy that up and manually lock the upper node. 246 * 247 * LAYERFS_UPPERLOCK already has the test, so we use it after copying 248 * up the v_vnlock from below. 249 */ 250 251 vp->v_vnlock = lowervp->v_vnlock; 252 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 253 KASSERT(error == 0); 254 255 /* 256 * Insert the new node into the hash. 257 * Add a reference to the lower node. 258 */ 259 260 *vpp = vp; 261 VREF(lowervp); 262 hd = LAYER_NHASH(lmp, lowervp); 263 LIST_INSERT_HEAD(hd, xp, layer_hash); 264 uvm_vnp_setsize(vp, 0); 265 mutex_exit(&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 mutex_enter(&lmp->layerm_hashlock); 288 aliasvp = layer_node_find(mp, lowervp); 289 if (aliasvp != NULL) { 290 /* 291 * layer_node_find has taken another reference 292 * to the alias vnode and moved the lock holding to 293 * aliasvp 294 */ 295 #ifdef LAYERFS_DIAGNOSTIC 296 if (layerfs_debug) 297 vprint("layer_node_create: exists", aliasvp); 298 #endif 299 } else { 300 int error; 301 302 mutex_exit(&lmp->layerm_hashlock); 303 304 /* 305 * Get new vnode. 306 */ 307 #ifdef LAYERFS_DIAGNOSTIC 308 if (layerfs_debug) 309 printf("layer_node_create: create new alias vnode\n"); 310 #endif 311 312 /* 313 * Make new vnode reference the layer_node. 314 */ 315 if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0) 316 return error; 317 318 /* 319 * aliasvp is already VREF'd by getnewvnode() 320 */ 321 } 322 323 /* 324 * Now that we have VREF'd the upper vnode, release the reference 325 * to the lower node. The existence of the layer_node retains one 326 * reference to the lower node. 327 */ 328 vrele(lowervp); 329 330 #ifdef DIAGNOSTIC 331 if (lowervp->v_usecount < 1) { 332 /* Should never happen... */ 333 vprint("layer_node_create: alias", aliasvp); 334 vprint("layer_node_create: lower", lowervp); 335 panic("layer_node_create: lower has 0 usecount."); 336 } 337 #endif 338 339 #ifdef LAYERFS_DIAGNOSTIC 340 if (layerfs_debug) 341 vprint("layer_node_create: alias", aliasvp); 342 #endif 343 *newvpp = aliasvp; 344 return (0); 345 } 346 347 #ifdef LAYERFS_DIAGNOSTIC 348 struct vnode * 349 layer_checkvp(vp, fil, lno) 350 struct vnode *vp; 351 const char *fil; 352 int lno; 353 { 354 struct layer_node *a = VTOLAYER(vp); 355 #ifdef notyet 356 /* 357 * Can't do this check because vop_reclaim runs 358 * with a funny vop vector. 359 * 360 * WRS - no it doesnt... 361 */ 362 if (vp->v_op != layer_vnodeop_p) { 363 printf ("layer_checkvp: on non-layer-node\n"); 364 #ifdef notyet 365 while (layer_checkvp_barrier) /*WAIT*/ ; 366 #endif 367 panic("layer_checkvp"); 368 }; 369 #endif 370 if (a->layer_lowervp == NULL) { 371 /* Should never happen */ 372 int i; u_long *p; 373 printf("vp = %p, ZERO ptr\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_checkvp"); 379 } 380 if (a->layer_lowervp->v_usecount < 1) { 381 int i; u_long *p; 382 printf("vp = %p, unref'ed lowervp\n", vp); 383 for (p = (u_long *) a, i = 0; i < 8; i++) 384 printf(" %lx", p[i]); 385 printf("\n"); 386 /* wait for debugger */ 387 panic ("layer with unref'ed lowervp"); 388 }; 389 #ifdef notnow 390 printf("layer %p/%d -> %p/%d [%s, %d]\n", 391 LAYERTOV(a), LAYERTOV(a)->v_usecount, 392 a->layer_lowervp, a->layer_lowervp->v_usecount, 393 fil, lno); 394 #endif 395 return a->layer_lowervp; 396 } 397 #endif 398
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