1 /* $NetBSD: layer_subr.c,v 1.35 2014/02/10 11:23:14 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 1.35 2014/02/10 11:23:14 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 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. 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 mutex_exit(&lmp->layerm_hashlock); 146 error = vget(vp, 0); 147 if (error) { 148 mutex_enter(&lmp->layerm_hashlock); 149 goto loop; 150 } 151 return vp; 152 } 153 return NULL; 154 } 155 156 /* 157 * layer_node_alloc: make a new layerfs vnode. 158 * 159 * => vp is the alias vnode, lowervp is the lower vnode. 160 * => We will hold a reference to lowervp. 161 */ 162 int 163 layer_node_alloc(struct mount *mp, struct vnode *lowervp, struct vnode **vpp) 164 { 165 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 166 struct layer_node_hashhead *hd; 167 struct layer_node *xp; 168 struct vnode *vp, *nvp; 169 int error; 170 171 /* Get a new vnode and share its interlock with underlying vnode. */ 172 error = getnewvnode(lmp->layerm_tag, mp, lmp->layerm_vnodeop_p, 173 lowervp->v_interlock, &vp); 174 if (error) { 175 return error; 176 } 177 vp->v_type = lowervp->v_type; 178 mutex_enter(vp->v_interlock); 179 vp->v_iflag |= VI_LAYER; 180 mutex_exit(vp->v_interlock); 181 182 xp = kmem_alloc(lmp->layerm_size, KM_SLEEP); 183 if (xp == NULL) { 184 ungetnewvnode(vp); 185 return ENOMEM; 186 } 187 if (vp->v_type == VBLK || vp->v_type == VCHR) { 188 spec_node_init(vp, lowervp->v_rdev); 189 } 190 191 /* 192 * Before inserting the node into the hash, check if other thread 193 * did not race with us. If so - return that node, destroy ours. 194 */ 195 mutex_enter(&lmp->layerm_hashlock); 196 if ((nvp = layer_node_find(mp, lowervp)) != NULL) { 197 ungetnewvnode(vp); 198 kmem_free(xp, lmp->layerm_size); 199 *vpp = nvp; 200 return 0; 201 } 202 203 vp->v_data = xp; 204 vp->v_vflag = (vp->v_vflag & ~VV_MPSAFE) | 205 (lowervp->v_vflag & VV_MPSAFE); 206 xp->layer_vnode = vp; 207 xp->layer_lowervp = lowervp; 208 xp->layer_flags = 0; 209 210 /* 211 * Insert the new node into the hash. 212 * Add a reference to the lower node. 213 */ 214 vref(lowervp); 215 hd = LAYER_NHASH(lmp, lowervp); 216 LIST_INSERT_HEAD(hd, xp, layer_hash); 217 uvm_vnp_setsize(vp, 0); 218 mutex_exit(&lmp->layerm_hashlock); 219 220 *vpp = vp; 221 return 0; 222 } 223 224 /* 225 * layer_node_create: try to find an existing layerfs vnode refering to it, 226 * otherwise make a new vnode which contains a reference to the lower vnode. 227 * 228 * => Caller should lock the lower node. 229 */ 230 int 231 layer_node_create(struct mount *mp, struct vnode *lowervp, struct vnode **nvpp) 232 { 233 struct vnode *aliasvp; 234 struct layer_mount *lmp = MOUNTTOLAYERMOUNT(mp); 235 236 mutex_enter(&lmp->layerm_hashlock); 237 aliasvp = layer_node_find(mp, lowervp); 238 if (aliasvp != NULL) { 239 /* 240 * Note: layer_node_find() has taken another reference to 241 * the alias vnode and moved the lock holding to aliasvp. 242 */ 243 #ifdef LAYERFS_DIAGNOSTIC 244 if (layerfs_debug) 245 vprint("layer_node_create: exists", aliasvp); 246 #endif 247 } else { 248 int error; 249 250 mutex_exit(&lmp->layerm_hashlock); 251 /* 252 * Get a new vnode. Make it to reference the layer_node. 253 * Note: aliasvp will be return with the reference held. 254 */ 255 error = (lmp->layerm_alloc)(mp, lowervp, &aliasvp); 256 if (error) 257 return error; 258 #ifdef LAYERFS_DIAGNOSTIC 259 if (layerfs_debug) 260 printf("layer_node_create: create new alias vnode\n"); 261 #endif 262 } 263 264 /* 265 * Now that we acquired a reference on the upper vnode, release one 266 * on the lower node. The existence of the layer_node retains one 267 * reference to the lower node. 268 */ 269 vrele(lowervp); 270 KASSERT(lowervp->v_usecount > 0); 271 272 #ifdef LAYERFS_DIAGNOSTIC 273 if (layerfs_debug) 274 vprint("layer_node_create: alias", aliasvp); 275 #endif 276 *nvpp = aliasvp; 277 return 0; 278 } 279 280 #ifdef LAYERFS_DIAGNOSTIC 281 struct vnode * 282 layer_checkvp(struct vnode *vp, const char *fil, int lno) 283 { 284 struct layer_node *a = VTOLAYER(vp); 285 #ifdef notyet 286 /* 287 * Can't do this check because vop_reclaim runs 288 * with a funny vop vector. 289 * 290 * WRS - no it doesnt... 291 */ 292 if (vp->v_op != layer_vnodeop_p) { 293 printf ("layer_checkvp: on non-layer-node\n"); 294 #ifdef notyet 295 while (layer_checkvp_barrier) /*WAIT*/ ; 296 #endif 297 panic("layer_checkvp"); 298 }; 299 #endif 300 if (a->layer_lowervp == NULL) { 301 /* Should never happen */ 302 int i; u_long *p; 303 printf("vp = %p, ZERO ptr\n", vp); 304 for (p = (u_long *) a, i = 0; i < 8; i++) 305 printf(" %lx", p[i]); 306 printf("\n"); 307 /* wait for debugger */ 308 panic("layer_checkvp"); 309 } 310 if (a->layer_lowervp->v_usecount < 1) { 311 int i; u_long *p; 312 printf("vp = %p, unref'ed lowervp\n", vp); 313 for (p = (u_long *) a, i = 0; i < 8; i++) 314 printf(" %lx", p[i]); 315 printf("\n"); 316 /* wait for debugger */ 317 panic ("layer with unref'ed lowervp"); 318 }; 319 #ifdef notnow 320 printf("layer %p/%d -> %p/%d [%s, %d]\n", 321 LAYERTOV(a), LAYERTOV(a)->v_usecount, 322 a->layer_lowervp, a->layer_lowervp->v_usecount, 323 fil, lno); 324 #endif 325 return a->layer_lowervp; 326 } 327 #endif 328