null_subr.c revision 143642
1/*- 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This code is derived from software donated to Berkeley by 6 * Jan-Simon Pendry. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)null_subr.c 8.7 (Berkeley) 5/14/95 33 * 34 * $FreeBSD: head/sys/fs/nullfs/null_subr.c 143642 2005-03-15 13:49:33Z jeff $ 35 */ 36 37#include <sys/param.h> 38#include <sys/systm.h> 39#include <sys/kernel.h> 40#include <sys/lock.h> 41#include <sys/mutex.h> 42#include <sys/malloc.h> 43#include <sys/mount.h> 44#include <sys/proc.h> 45#include <sys/vnode.h> 46 47#include <fs/nullfs/null.h> 48 49#define LOG2_SIZEVNODE 8 /* log2(sizeof struct vnode) */ 50#define NNULLNODECACHE 16 51 52/* 53 * Null layer cache: 54 * Each cache entry holds a reference to the lower vnode 55 * along with a pointer to the alias vnode. When an 56 * entry is added the lower vnode is VREF'd. When the 57 * alias is removed the lower vnode is vrele'd. 58 */ 59 60#define NULL_NHASH(vp) \ 61 (&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash]) 62 63static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl; 64static u_long null_node_hash; 65struct mtx null_hashmtx; 66 67static MALLOC_DEFINE(M_NULLFSHASH, "NULLFS hash", "NULLFS hash table"); 68MALLOC_DEFINE(M_NULLFSNODE, "NULLFS node", "NULLFS vnode private part"); 69 70static struct vnode * null_hashget(struct mount *, struct vnode *); 71static struct vnode * null_hashins(struct mount *, struct null_node *); 72 73/* 74 * Initialise cache headers 75 */ 76int 77nullfs_init(vfsp) 78 struct vfsconf *vfsp; 79{ 80 81 NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */ 82 null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash); 83 mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF); 84 return (0); 85} 86 87int 88nullfs_uninit(vfsp) 89 struct vfsconf *vfsp; 90{ 91 92 mtx_destroy(&null_hashmtx); 93 free(null_node_hashtbl, M_NULLFSHASH); 94 return (0); 95} 96 97/* 98 * Return a VREF'ed alias for lower vnode if already exists, else 0. 99 * Lower vnode should be locked on entry and will be left locked on exit. 100 */ 101static struct vnode * 102null_hashget(mp, lowervp) 103 struct mount *mp; 104 struct vnode *lowervp; 105{ 106 struct thread *td = curthread; /* XXX */ 107 struct null_node_hashhead *hd; 108 struct null_node *a; 109 struct vnode *vp; 110 111 /* 112 * Find hash base, and then search the (two-way) linked 113 * list looking for a null_node structure which is referencing 114 * the lower vnode. If found, the increment the null_node 115 * reference count (but NOT the lower vnode's VREF counter). 116 */ 117 hd = NULL_NHASH(lowervp); 118loop: 119 mtx_lock(&null_hashmtx); 120 LIST_FOREACH(a, hd, null_hash) { 121 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) { 122 vp = NULLTOV(a); 123 VI_LOCK(vp); 124 /* 125 * If the nullfs node is being recycled we have 126 * to wait until it finishes prior to scanning 127 * again. 128 */ 129 mtx_unlock(&null_hashmtx); 130 if ((vp->v_iflag & VI_DOOMED) != 0) { 131 /* Wait for recycling to finish. */ 132 VOP_LOCK(vp, LK_EXCLUSIVE|LK_INTERLOCK, td); 133 VOP_UNLOCK(vp, 0, td); 134 goto loop; 135 } 136 vget(vp, LK_INTERLOCK, td); 137 return (vp); 138 } 139 } 140 mtx_unlock(&null_hashmtx); 141 return (NULLVP); 142} 143 144/* 145 * Act like null_hashget, but add passed null_node to hash if no existing 146 * node found. 147 */ 148static struct vnode * 149null_hashins(mp, xp) 150 struct mount *mp; 151 struct null_node *xp; 152{ 153 struct thread *td = curthread; /* XXX */ 154 struct null_node_hashhead *hd; 155 struct null_node *oxp; 156 struct vnode *ovp; 157 158 hd = NULL_NHASH(xp->null_lowervp); 159loop: 160 mtx_lock(&null_hashmtx); 161 LIST_FOREACH(oxp, hd, null_hash) { 162 if (oxp->null_lowervp == xp->null_lowervp && 163 NULLTOV(oxp)->v_mount == mp) { 164 ovp = NULLTOV(oxp); 165 VI_LOCK(ovp); 166 /* 167 * If the nullfs node is being recycled we have 168 * to wait until it finishes prior to scanning 169 * again. 170 */ 171 mtx_unlock(&null_hashmtx); 172 if ((ovp->v_iflag & VI_DOOMED) != 0) { 173 VOP_LOCK(ovp, LK_EXCLUSIVE|LK_INTERLOCK, td); 174 VOP_UNLOCK(ovp, 0, td); 175 goto loop; 176 } 177 vget(ovp, LK_INTERLOCK, td); 178 return (ovp); 179 } 180 } 181 LIST_INSERT_HEAD(hd, xp, null_hash); 182 mtx_unlock(&null_hashmtx); 183 return (NULLVP); 184} 185 186/* 187 * Make a new or get existing nullfs node. 188 * Vp is the alias vnode, lowervp is the lower vnode. 189 * 190 * The lowervp assumed to be locked and having "spare" reference. This routine 191 * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers" 192 * the caller's "spare" reference to created nullfs vnode. 193 */ 194int 195null_nodeget(mp, lowervp, vpp) 196 struct mount *mp; 197 struct vnode *lowervp; 198 struct vnode **vpp; 199{ 200 struct null_node *xp; 201 struct vnode *vp; 202 int error; 203 204 /* Lookup the hash firstly */ 205 *vpp = null_hashget(mp, lowervp); 206 if (*vpp != NULL) { 207 vrele(lowervp); 208 return (0); 209 } 210 211 /* 212 * We do not serialize vnode creation, instead we will check for 213 * duplicates later, when adding new vnode to hash. 214 * 215 * Note that duplicate can only appear in hash if the lowervp is 216 * locked LK_SHARED. 217 */ 218 219 /* 220 * Do the MALLOC before the getnewvnode since doing so afterward 221 * might cause a bogus v_data pointer to get dereferenced 222 * elsewhere if MALLOC should block. 223 */ 224 MALLOC(xp, struct null_node *, sizeof(struct null_node), 225 M_NULLFSNODE, M_WAITOK); 226 227 error = getnewvnode("null", mp, &null_vnodeops, &vp); 228 if (error) { 229 FREE(xp, M_NULLFSNODE); 230 return (error); 231 } 232 233 xp->null_vnode = vp; 234 xp->null_lowervp = lowervp; 235 vp->v_type = lowervp->v_type; 236 vp->v_data = xp; 237 vp->v_vnlock = lowervp->v_vnlock; 238 if (vp->v_vnlock == NULL) 239 panic("null_nodeget: Passed a NULL vnlock.\n"); 240 /* 241 * Atomically insert our new node into the hash or vget existing 242 * if someone else has beaten us to it. 243 */ 244 *vpp = null_hashins(mp, xp); 245 if (*vpp != NULL) { 246 vrele(lowervp); 247 vp->v_vnlock = &vp->v_lock; 248 xp->null_lowervp = NULL; 249 vrele(vp); 250 return (0); 251 } 252 *vpp = vp; 253 254 return (0); 255} 256 257/* 258 * Remove node from hash. 259 */ 260void 261null_hashrem(xp) 262 struct null_node *xp; 263{ 264 265 mtx_lock(&null_hashmtx); 266 LIST_REMOVE(xp, null_hash); 267 mtx_unlock(&null_hashmtx); 268} 269 270#ifdef DIAGNOSTIC 271 272#ifdef KDB 273#define null_checkvp_barrier 1 274#else 275#define null_checkvp_barrier 0 276#endif 277 278struct vnode * 279null_checkvp(vp, fil, lno) 280 struct vnode *vp; 281 char *fil; 282 int lno; 283{ 284 struct null_node *a = VTONULL(vp); 285#ifdef notyet 286 /* 287 * Can't do this check because vop_reclaim runs 288 * with a funny vop vector. 289 */ 290 if (vp->v_op != null_vnodeop_p) { 291 printf ("null_checkvp: on non-null-node\n"); 292 while (null_checkvp_barrier) /*WAIT*/ ; 293 panic("null_checkvp"); 294 }; 295#endif 296 if (a->null_lowervp == NULLVP) { 297 /* Should never happen */ 298 int i; u_long *p; 299 printf("vp = %p, ZERO ptr\n", (void *)vp); 300 for (p = (u_long *) a, i = 0; i < 8; i++) 301 printf(" %lx", p[i]); 302 printf("\n"); 303 /* wait for debugger */ 304 while (null_checkvp_barrier) /*WAIT*/ ; 305 panic("null_checkvp"); 306 } 307 if (vrefcnt(a->null_lowervp) < 1) { 308 int i; u_long *p; 309 printf("vp = %p, unref'ed lowervp\n", (void *)vp); 310 for (p = (u_long *) a, i = 0; i < 8; i++) 311 printf(" %lx", p[i]); 312 printf("\n"); 313 /* wait for debugger */ 314 while (null_checkvp_barrier) /*WAIT*/ ; 315 panic ("null with unref'ed lowervp"); 316 }; 317#ifdef notyet 318 printf("null %x/%d -> %x/%d [%s, %d]\n", 319 NULLTOV(a), vrefcnt(NULLTOV(a)), 320 a->null_lowervp, vrefcnt(a->null_lowervp), 321 fil, lno); 322#endif 323 return a->null_lowervp; 324} 325#endif 326