1 /* $NetBSD: layer_subr.c,v 1.27 2009/03/15 17:22:38 cegger 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 1.27 2009/03/15 17:22:38 cegger 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(void) 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(void) 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(struct mount *mp, 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 mutex_enter(&vp->v_interlock); 152 /* 153 * If we find a node being cleaned out, then 154 * ignore it and continue. A thread trying to 155 * clean out the extant layer vnode needs to 156 * acquire the shared lock (i.e. the lower 157 * vnode's lock), which our caller already holds. 158 * To allow the cleaning to succeed the current 159 * thread must make progress. So, for a brief 160 * time more than one vnode in a layered file 161 * system may refer to a single vnode in the 162 * lower file system. 163 */ 164 if ((vp->v_iflag & VI_XLOCK) != 0) { 165 mutex_exit(&vp->v_interlock); 166 continue; 167 } 168 mutex_exit(&lmp->layerm_hashlock); 169 /* 170 * We must not let vget() try to lock the layer 171 * vp, since the lower vp is already locked and 172 * locking the layer vp will involve locking 173 * the lower vp (whether or not they actually 174 * share a lock). Instead, take the layer vp's 175 * lock separately afterward, but only if it 176 * does not share the lower vp's lock. 177 */ 178 error = vget(vp, LK_INTERLOCK | LK_NOWAIT); 179 if (error) { 180 kpause("layerfs", false, 1, NULL); 181 mutex_enter(&lmp->layerm_hashlock); 182 goto loop; 183 } 184 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 185 return (vp); 186 } 187 } 188 return NULL; 189 } 190 191 192 /* 193 * Make a new layer_node node. 194 * Vp is the alias vnode, lowervp is the lower vnode. 195 * Maintain a reference to lowervp. 196 */ 197 int 198 layer_node_alloc(struct mount *mp, struct vnode *lowervp, struct vnode **vpp) 199 { 200 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 201 struct layer_node_hashhead *hd; 202 struct layer_node *xp; 203 struct vnode *vp, *nvp; 204 int error; 205 extern int (**dead_vnodeop_p)(void *); 206 207 error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp); 208 if (error != 0) 209 return (error); 210 vp->v_type = lowervp->v_type; 211 mutex_enter(&vp->v_interlock); 212 vp->v_iflag |= VI_LAYER; 213 mutex_exit(&vp->v_interlock); 214 215 xp = kmem_alloc(lmp->layerm_size, KM_SLEEP); 216 if (xp == NULL) { 217 ungetnewvnode(vp); 218 return ENOMEM; 219 } 220 if (vp->v_type == VBLK || vp->v_type == VCHR) { 221 spec_node_init(vp, lowervp->v_rdev); 222 } 223 224 vp->v_data = xp; 225 vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) | 226 (lowervp->v_vflag & VV_MPSAFE); 227 xp->layer_vnode = vp; 228 xp->layer_lowervp = lowervp; 229 xp->layer_flags = 0; 230 231 /* 232 * Before we insert our new node onto the hash chains, 233 * check to see if someone else has beaten us to it. 234 * (We could have slept in MALLOC.) 235 */ 236 mutex_enter(&lmp->layerm_hashlock); 237 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 238 *vpp = nvp; 239 240 /* free the substructures we've allocated. */ 241 kmem_free(xp, lmp->layerm_size); 242 if (vp->v_type == VBLK || vp->v_type == VCHR) 243 spec_node_destroy(vp); 244 245 vp->v_type = VBAD; /* node is discarded */ 246 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 247 vrele(vp); /* get rid of it. */ 248 return (0); 249 } 250 251 /* 252 * Now lock the new node. We rely on the fact that we were passed 253 * a locked vnode. If the lower node is exporting a struct lock 254 * (v_vnlock != NULL) then we just set the upper v_vnlock to the 255 * lower one, and both are now locked. If the lower node is exporting 256 * NULL, then we copy that up and manually lock the upper node. 257 * 258 * LAYERFS_UPPERLOCK already has the test, so we use it after copying 259 * up the v_vnlock from below. 260 */ 261 262 vp->v_vnlock = lowervp->v_vnlock; 263 LAYERFS_UPPERLOCK(vp, LK_EXCLUSIVE, error); 264 KASSERT(error == 0); 265 266 /* 267 * Insert the new node into the hash. 268 * Add a reference to the lower node. 269 */ 270 271 *vpp = vp; 272 VREF(lowervp); 273 hd = LAYER_NHASH(lmp, lowervp); 274 LIST_INSERT_HEAD(hd, xp, layer_hash); 275 uvm_vnp_setsize(vp, 0); 276 mutex_exit(&lmp->layerm_hashlock); 277 return (0); 278 } 279 280 281 /* 282 * Try to find an existing layer_node vnode refering 283 * to it, otherwise make a new layer_node vnode which 284 * contains a reference to the lower vnode. 285 * 286 * >>> we assume that the lower node is already locked upon entry, so we 287 * propagate the lock state to upper node << 288 */ 289 int 290 layer_node_create(struct mount *mp, struct vnode *lowervp, struct vnode **newvpp) 291 { 292 struct vnode *aliasvp; 293 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 294 295 mutex_enter(&lmp->layerm_hashlock); 296 aliasvp = layer_node_find(mp, lowervp); 297 if (aliasvp != 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 if (layerfs_debug) 305 vprint("layer_node_create: exists", aliasvp); 306 #endif 307 } else { 308 int error; 309 310 mutex_exit(&lmp->layerm_hashlock); 311 312 /* 313 * Get new vnode. 314 */ 315 #ifdef LAYERFS_DIAGNOSTIC 316 if (layerfs_debug) 317 printf("layer_node_create: create new alias vnode\n"); 318 #endif 319 320 /* 321 * Make new vnode reference the layer_node. 322 */ 323 if ((error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp)) != 0) 324 return error; 325 326 /* 327 * aliasvp is already VREF'd by getnewvnode() 328 */ 329 } 330 331 /* 332 * Now that we have VREF'd the upper vnode, release the reference 333 * to the lower node. The existence of the layer_node retains one 334 * reference to the lower node. 335 */ 336 vrele(lowervp); 337 338 #ifdef DIAGNOSTIC 339 if (lowervp->v_usecount < 1) { 340 /* Should never happen... */ 341 vprint("layer_node_create: alias", aliasvp); 342 vprint("layer_node_create: lower", lowervp); 343 panic("layer_node_create: lower has 0 usecount."); 344 } 345 #endif 346 347 #ifdef LAYERFS_DIAGNOSTIC 348 if (layerfs_debug) 349 vprint("layer_node_create: alias", aliasvp); 350 #endif 351 *newvpp = aliasvp; 352 return (0); 353 } 354 355 #ifdef LAYERFS_DIAGNOSTIC 356 struct vnode * 357 layer_checkvp(struct vnode *vp, const char *fil, int lno) 358 { 359 struct layer_node *a = VTOLAYER(vp); 360 #ifdef notyet 361 /* 362 * Can't do this check because vop_reclaim runs 363 * with a funny vop vector. 364 * 365 * WRS - no it doesnt... 366 */ 367 if (vp->v_op != layer_vnodeop_p) { 368 printf ("layer_checkvp: on non-layer-node\n"); 369 #ifdef notyet 370 while (layer_checkvp_barrier) /*WAIT*/ ; 371 #endif 372 panic("layer_checkvp"); 373 }; 374 #endif 375 if (a->layer_lowervp == NULL) { 376 /* Should never happen */ 377 int i; u_long *p; 378 printf("vp = %p, ZERO ptr\n", vp); 379 for (p = (u_long *) a, i = 0; i < 8; i++) 380 printf(" %lx", p[i]); 381 printf("\n"); 382 /* wait for debugger */ 383 panic("layer_checkvp"); 384 } 385 if (a->layer_lowervp->v_usecount < 1) { 386 int i; u_long *p; 387 printf("vp = %p, unref'ed lowervp\n", vp); 388 for (p = (u_long *) a, i = 0; i < 8; i++) 389 printf(" %lx", p[i]); 390 printf("\n"); 391 /* wait for debugger */ 392 panic ("layer with unref'ed lowervp"); 393 }; 394 #ifdef notnow 395 printf("layer %p/%d -> %p/%d [%s, %d]\n", 396 LAYERTOV(a), LAYERTOV(a)->v_usecount, 397 a->layer_lowervp, a->layer_lowervp->v_usecount, 398 fil, lno); 399 #endif 400 return a->layer_lowervp; 401 } 402 #endif 403