layer_subr.c revision 1.31.6.1
1 /* $NetBSD: layer_subr.c,v 1.31.6.1 2011/06/23 14:20:24 cherry 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 1.31.6.1 2011/06/23 14:20:24 cherry 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 /* Get a new vnode and share its interlock with underlying vnode. */ 193 error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, 194 lowervp->v_interlock, &vp); 195 if (error) { 196 return error; 197 } 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 spec_node_init(vp, lowervp->v_rdev); 210 } 211 212 vp->v_data = xp; 213 vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) | 214 (lowervp->v_vflag & VV_MPSAFE); 215 xp->layer_vnode = vp; 216 xp->layer_lowervp = lowervp; 217 xp->layer_flags = 0; 218 219 /* 220 * Before inserting the node into the hash, check if other thread 221 * did not race with us. If so - return that node, destroy ours. 222 */ 223 mutex_enter(&lmp->layerm_hashlock); 224 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 225 /* Free the structures we have created. */ 226 if (vp->v_type == VBLK || vp->v_type == VCHR) 227 spec_node_destroy(vp); 228 229 vp->v_type = VBAD; /* node is discarded */ 230 vp->v_op = dead_vnodeop_p; /* so ops will still work */ 231 vrele(vp); /* get rid of it. */ 232 kmem_free(xp, lmp->layerm_size); 233 *vpp = nvp; 234 return 0; 235 } 236 237 /* 238 * Insert the new node into the hash. 239 * Add a reference to the lower node. 240 */ 241 vref(lowervp); 242 hd = LAYER_NHASH(lmp, lowervp); 243 LIST_INSERT_HEAD(hd, xp, layer_hash); 244 uvm_vnp_setsize(vp, 0); 245 mutex_exit(&lmp->layerm_hashlock); 246 247 *vpp = vp; 248 return 0; 249 } 250 251 /* 252 * layer_node_create: try to find an existing layerfs vnode refering to it, 253 * otherwise make a new vnode which contains a reference to the lower vnode. 254 * 255 * => Caller should lock the lower node. 256 */ 257 int 258 layer_node_create(struct mount *mp, struct vnode *lowervp, struct vnode **nvpp) 259 { 260 struct vnode *aliasvp; 261 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 262 263 KASSERT(VOP_ISLOCKED(lowervp)); 264 265 mutex_enter(&lmp->layerm_hashlock); 266 aliasvp = layer_node_find(mp, lowervp); 267 if (aliasvp != NULL) { 268 /* 269 * Note: layer_node_find() has taken another reference to 270 * the alias vnode and moved the lock holding to aliasvp. 271 */ 272 #ifdef LAYERFS_DIAGNOSTIC 273 if (layerfs_debug) 274 vprint("layer_node_create: exists", aliasvp); 275 #endif 276 } else { 277 int error; 278 279 mutex_exit(&lmp->layerm_hashlock); 280 /* 281 * Get a new vnode. Make it to reference the layer_node. 282 * Note: aliasvp will be return with the reference held. 283 */ 284 error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp); 285 if (error) 286 return error; 287 #ifdef LAYERFS_DIAGNOSTIC 288 if (layerfs_debug) 289 printf("layer_node_create: create new alias vnode\n"); 290 #endif 291 } 292 293 /* 294 * Now that we acquired a reference on the upper vnode, release one 295 * on the lower node. The existence of the layer_node retains one 296 * reference to the lower node. 297 */ 298 vrele(lowervp); 299 KASSERT(lowervp->v_usecount > 0); 300 301 #ifdef LAYERFS_DIAGNOSTIC 302 if (layerfs_debug) 303 vprint("layer_node_create: alias", aliasvp); 304 #endif 305 *nvpp = aliasvp; 306 return 0; 307 } 308 309 #ifdef LAYERFS_DIAGNOSTIC 310 struct vnode * 311 layer_checkvp(struct vnode *vp, const char *fil, int lno) 312 { 313 struct layer_node *a = VTOLAYER(vp); 314 #ifdef notyet 315 /* 316 * Can't do this check because vop_reclaim runs 317 * with a funny vop vector. 318 * 319 * WRS - no it doesnt... 320 */ 321 if (vp->v_op != layer_vnodeop_p) { 322 printf ("layer_checkvp: on non-layer-node\n"); 323 #ifdef notyet 324 while (layer_checkvp_barrier) /*WAIT*/ ; 325 #endif 326 panic("layer_checkvp"); 327 }; 328 #endif 329 if (a->layer_lowervp == NULL) { 330 /* Should never happen */ 331 int i; u_long *p; 332 printf("vp = %p, ZERO ptr\n", vp); 333 for (p = (u_long *) a, i = 0; i < 8; i++) 334 printf(" %lx", p[i]); 335 printf("\n"); 336 /* wait for debugger */ 337 panic("layer_checkvp"); 338 } 339 if (a->layer_lowervp->v_usecount < 1) { 340 int i; u_long *p; 341 printf("vp = %p, unref'ed lowervp\n", vp); 342 for (p = (u_long *) a, i = 0; i < 8; i++) 343 printf(" %lx", p[i]); 344 printf("\n"); 345 /* wait for debugger */ 346 panic ("layer with unref'ed lowervp"); 347 }; 348 #ifdef notnow 349 printf("layer %p/%d -> %p/%d [%s, %d]\n", 350 LAYERTOV(a), LAYERTOV(a)->v_usecount, 351 a->layer_lowervp, a->layer_lowervp->v_usecount, 352 fil, lno); 353 #endif 354 return a->layer_lowervp; 355 } 356 #endif 357
Indexes created Thu Oct 02 14:10:14 GMT 2025