1 /* $NetBSD: layer_subr.c,v 1.31 2010/07/21 17:52:12 hannken 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 /* 37 * Copyright (c) 1992, 1993 38 * The Regents of the University of California. All rights reserved. 39 * 40 * This code is derived from software donated to Berkeley by 41 * Jan-Simon Pendry. 42 * 43 * Redistribution and use in source and binary forms, with or without 44 * modification, are permitted provided that the following conditions 45 * are met: 46 * 1. Redistributions of source code must retain the above copyright 47 * notice, this list of conditions and the following disclaimer. 48 * 2. Redistributions in binary form must reproduce the above copyright 49 * notice, this list of conditions and the following disclaimer in the 50 * documentation and/or other materials provided with the distribution. 51 * 3. Neither the name of the University nor the names of its contributors 52 * may be used to endorse or promote products derived from this software 53 * without specific prior written permission. 54 * 55 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 56 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 57 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 58 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 59 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 60 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 61 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 62 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 63 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 64 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 65 * SUCH DAMAGE. 66 * 67 * from: Id: lofs_subr.c,v 1.11 1992/05/30 10:05:43 jsp Exp 68 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 69 */ 70 71 #include <sys/cdefs.h> 72 __KERNEL_RCSID(0, "$NetBSD: layer_subr.c,v 1.31 2010/07/21 17:52:12 hannken Exp $"); 73 74 #include <sys/param.h> 75 #include <sys/systm.h> 76 #include <sys/proc.h> 77 #include <sys/time.h> 78 #include <sys/vnode.h> 79 #include <sys/mount.h> 80 #include <sys/namei.h> 81 #include <sys/kmem.h> 82 #include <sys/malloc.h> 83 84 #include <miscfs/specfs/specdev.h> 85 #include <miscfs/genfs/layer.h> 86 #include <miscfs/genfs/layer_extern.h> 87 88 #ifdef LAYERFS_DIAGNOSTIC 89 int layerfs_debug = 1; 90 #endif 91 92 /* 93 * layer cache: 94 * Each cache entry holds a reference to the lower vnode 95 * along with a pointer to the alias vnode. When an 96 * entry is added the lower vnode is VREF'd. When the 97 * alias is removed the lower vnode is vrele'd. 98 */ 99 100 void 101 layerfs_init(void) 102 { 103 /* Nothing. */ 104 } 105 106 void 107 layerfs_done(void) 108 { 109 /* Nothing. */ 110 } 111 112 /* 113 * layer_node_find: find and return alias for lower vnode or NULL. 114 * 115 * => Return alias vnode locked and referenced. if already exists. 116 * => The layermp's hashlock must be held on entry, we will unlock on success. 117 */ 118 struct vnode * 119 layer_node_find(struct mount *mp, struct vnode *lowervp) 120 { 121 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 122 struct layer_node_hashhead *hd; 123 struct layer_node *a; 124 struct vnode *vp; 125 int error; 126 127 /* 128 * Find hash bucket and search the (two-way) linked list looking 129 * for a layerfs node structure which is referencing the lower vnode. 130 * If found, the increment the layer_node reference count, but NOT 131 * the lower vnode's reference counter. Return vnode locked. 132 */ 133 KASSERT(mutex_owned(&lmp->layerm_hashlock)); 134 hd = LAYER_NHASH(lmp, lowervp); 135 loop: 136 LIST_FOREACH(a, hd, layer_hash) { 137 if (a->layer_lowervp != lowervp) { 138 continue; 139 } 140 vp = LAYERTOV(a); 141 if (vp->v_mount != mp) { 142 continue; 143 } 144 mutex_enter(&vp->v_interlock); 145 /* 146 * If we find a node being cleaned out, then ignore it and 147 * continue. A thread trying to clean out the extant layer 148 * vnode needs to acquire the shared lock (i.e. the lower 149 * vnode's lock), which our caller already holds. To allow 150 * the cleaning to succeed the current thread must make 151 * progress. So, for a brief time more than one vnode in a 152 * layered file system may refer to a single vnode in the 153 * lower file system. 154 */ 155 if ((vp->v_iflag & VI_XLOCK) != 0) { 156 mutex_exit(&vp->v_interlock); 157 continue; 158 } 159 mutex_exit(&lmp->layerm_hashlock); 160 /* 161 * We must not let vget() try to lock the layer vp, since 162 * the lower vp is already locked and locking the layer vp 163 * will involve locking the lower vp. 164 */ 165 error = vget(vp, LK_NOWAIT); 166 if (error) { 167 kpause("layerfs", false, 1, NULL); 168 mutex_enter(&lmp->layerm_hashlock); 169 goto loop; 170 } 171 return vp; 172 } 173 return NULL; 174 } 175 176 /* 177 * layer_node_alloc: make a new layerfs vnode. 178 * 179 * => vp is the alias vnode, lowervp is the lower vnode. 180 * => We will hold a reference to lowervp. 181 */ 182 int 183 layer_node_alloc(struct mount *mp, struct vnode *lowervp, 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 error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, &vp); 193 if (error) { 194 return error; 195 } 196 vp->v_type = lowervp->v_type; 197 mutex_enter(&vp->v_interlock); 198 vp->v_iflag |= VI_LAYER; 199 mutex_exit(&vp->v_interlock); 200 201 xp = kmem_alloc(lmp->layerm_size, KM_SLEEP); 202 if (xp == NULL) { 203 ungetnewvnode(vp); 204 return ENOMEM; 205 } 206 if (vp->v_type == VBLK || vp->v_type == VCHR) { 207 spec_node_init(vp, lowervp->v_rdev); 208 } 209 210 vp->v_data = xp; 211 vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) | 212 (lowervp->v_vflag & VV_MPSAFE); 213 xp->layer_vnode = vp; 214 xp->layer_lowervp = lowervp; 215 xp->layer_flags = 0; 216 217 /* 218 * Before inserting the node into the hash, check if other thread 219 * did not race with us. If so - return that node, destroy ours. 220 */ 221 mutex_enter(&lmp->layerm_hashlock); 222 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 223 /* Free the structures we have created. */ 224 if (vp->v_type == VBLK || vp->v_type == VCHR) 225 spec_node_destroy(vp); 226 227 vp->v_type = VBAD; /* node is discarded */ 228 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 229 vrele(vp); /* get rid of it. */ 230 kmem_free(xp, lmp->layerm_size); 231 *vpp = nvp; 232 return 0; 233 } 234 235 /* 236 * Insert the new node into the hash. 237 * Add a reference to the lower node. 238 */ 239 vref(lowervp); 240 hd = LAYER_NHASH(lmp, lowervp); 241 LIST_INSERT_HEAD(hd, xp, layer_hash); 242 uvm_vnp_setsize(vp, 0); 243 mutex_exit(&lmp->layerm_hashlock); 244 245 *vpp = vp; 246 return 0; 247 } 248 249 /* 250 * layer_node_create: try to find an existing layerfs vnode refering to it, 251 * otherwise make a new vnode which contains a reference to the lower vnode. 252 * 253 * => Caller should lock the lower node. 254 */ 255 int 256 layer_node_create(struct mount *mp, struct vnode *lowervp, struct vnode **nvpp) 257 { 258 struct vnode *aliasvp; 259 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 260 261 KASSERT(VOP_ISLOCKED(lowervp)); 262 263 mutex_enter(&lmp->layerm_hashlock); 264 aliasvp = layer_node_find(mp, lowervp); 265 if (aliasvp != NULL) { 266 /* 267 * Note: layer_node_find() has taken another reference to 268 * the alias vnode and moved the lock holding to aliasvp. 269 */ 270 #ifdef LAYERFS_DIAGNOSTIC 271 if (layerfs_debug) 272 vprint("layer_node_create: exists", aliasvp); 273 #endif 274 } else { 275 int error; 276 277 mutex_exit(&lmp->layerm_hashlock); 278 /* 279 * Get a new vnode. Make it to reference the layer_node. 280 * Note: aliasvp will be return with the reference held. 281 */ 282 error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp); 283 if (error) 284 return error; 285 #ifdef LAYERFS_DIAGNOSTIC 286 if (layerfs_debug) 287 printf("layer_node_create: create new alias vnode\n"); 288 #endif 289 } 290 291 /* 292 * Now that we acquired a reference on the upper vnode, release one 293 * on the lower node. The existence of the layer_node retains one 294 * reference to the lower node. 295 */ 296 vrele(lowervp); 297 KASSERT(lowervp->v_usecount > 0); 298 299 #ifdef LAYERFS_DIAGNOSTIC 300 if (layerfs_debug) 301 vprint("layer_node_create: alias", aliasvp); 302 #endif 303 *nvpp = aliasvp; 304 return 0; 305 } 306 307 #ifdef LAYERFS_DIAGNOSTIC 308 struct vnode * 309 layer_checkvp(struct vnode *vp, const char *fil, int lno) 310 { 311 struct layer_node *a = VTOLAYER(vp); 312 #ifdef notyet 313 /* 314 * Can't do this check because vop_reclaim runs 315 * with a funny vop vector. 316 * 317 * WRS - no it doesnt... 318 */ 319 if (vp->v_op != layer_vnodeop_p) { 320 printf ("layer_checkvp: on non-layer-node\n"); 321 #ifdef notyet 322 while (layer_checkvp_barrier) /*WAIT*/ ; 323 #endif 324 panic("layer_checkvp"); 325 }; 326 #endif 327 if (a->layer_lowervp == NULL) { 328 /* Should never happen */ 329 int i; u_long *p; 330 printf("vp = %p, ZERO ptr\n", vp); 331 for (p = (u_long *) a, i = 0; i < 8; i++) 332 printf(" %lx", p[i]); 333 printf("\n"); 334 /* wait for debugger */ 335 panic("layer_checkvp"); 336 } 337 if (a->layer_lowervp->v_usecount < 1) { 338 int i; u_long *p; 339 printf("vp = %p, unref'ed lowervp\n", vp); 340 for (p = (u_long *) a, i = 0; i < 8; i++) 341 printf(" %lx", p[i]); 342 printf("\n"); 343 /* wait for debugger */ 344 panic ("layer with unref'ed lowervp"); 345 }; 346 #ifdef notnow 347 printf("layer %p/%d -> %p/%d [%s, %d]\n", 348 LAYERTOV(a), LAYERTOV(a)->v_usecount, 349 a->layer_lowervp, a->layer_lowervp->v_usecount, 350 fil, lno); 351 #endif 352 return a->layer_lowervp; 353 } 354 #endif 355