sys/kern/vfs_hash.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2005 Poul-Henning Kamp
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  *
  28  */
  29
  30 #include <sys/cdefs.h>
  31 __FBSDID("$FreeBSD$");
  32
  33 #include <sys/param.h>
  34 #include <sys/systm.h>
  35 #include <sys/kernel.h>
  36 #include <sys/malloc.h>
  37 #include <sys/mount.h>
  38 #include <sys/rwlock.h>
  39 #include <sys/vnode.h>
  40
  41 static MALLOC_DEFINE(M_VFS_HASH, "vfs_hash", "VFS hash table");
  42
  43 static LIST_HEAD(vfs_hash_head, vnode)  *vfs_hash_tbl;
  44 static LIST_HEAD(,vnode)                vfs_hash_side;
  45 static u_long                           vfs_hash_mask;
  46 static struct rwlock                    vfs_hash_lock;
  47
  48 static void
  49 vfs_hashinit(void *dummy __unused)
  50 {
  51
  52         vfs_hash_tbl = hashinit(desiredvnodes, M_VFS_HASH, &vfs_hash_mask);
  53         rw_init(&vfs_hash_lock, "vfs hash");
  54         LIST_INIT(&vfs_hash_side);
  55 }
  56
  57 /* Must be SI_ORDER_SECOND so desiredvnodes is available */
  58 SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL);
  59
  60 u_int
  61 vfs_hash_index(struct vnode *vp)
  62 {
  63
  64         return (vp->v_hash + vp->v_mount->mnt_hashseed);
  65 }
  66
  67 static struct vfs_hash_head *
  68 vfs_hash_bucket(const struct mount *mp, u_int hash)
  69 {
  70
  71         return (&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
  72 }
  73
  74 int
  75 vfs_hash_get(const struct mount *mp, u_int hash, int flags, struct thread *td,
  76     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
  77 {
  78         struct vnode *vp;
  79         int error;
  80
  81         while (1) {
  82                 rw_rlock(&vfs_hash_lock);
  83                 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
  84                         if (vp->v_hash != hash)
  85                                 continue;
  86                         if (vp->v_mount != mp)
  87                                 continue;
  88                         if (fn != NULL && fn(vp, arg))
  89                                 continue;
  90                         vhold(vp);
  91                         rw_runlock(&vfs_hash_lock);
  92                         error = vget(vp, flags | LK_VNHELD, td);
  93                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
  94                                 break;
  95                         if (error)
  96                                 return (error);
  97                         *vpp = vp;
  98                         return (0);
  99                 }
 100                 if (vp == NULL) {
 101                         rw_runlock(&vfs_hash_lock);
 102                         *vpp = NULL;
 103                         return (0);
 104                 }
 105         }
 106 }
 107
 108 void
 109 vfs_hash_ref(const struct mount *mp, u_int hash, struct thread *td,
 110     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
 111 {
 112         struct vnode *vp;
 113
 114         while (1) {
 115                 rw_rlock(&vfs_hash_lock);
 116                 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
 117                         if (vp->v_hash != hash)
 118                                 continue;
 119                         if (vp->v_mount != mp)
 120                                 continue;
 121                         if (fn != NULL && fn(vp, arg))
 122                                 continue;
 123                         vhold(vp);
 124                         rw_runlock(&vfs_hash_lock);
 125                         vref(vp);
 126                         vdrop(vp);
 127                         *vpp = vp;
 128                         return;
 129                 }
 130                 if (vp == NULL) {
 131                         rw_runlock(&vfs_hash_lock);
 132                         *vpp = NULL;
 133                         return;
 134                 }
 135         }
 136 }
 137
 138 void
 139 vfs_hash_remove(struct vnode *vp)
 140 {
 141
 142         rw_wlock(&vfs_hash_lock);
 143         LIST_REMOVE(vp, v_hashlist);
 144         rw_wunlock(&vfs_hash_lock);
 145 }
 146
 147 int
 148 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td,
 149     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
 150 {
 151         struct vnode *vp2;
 152         int error;
 153
 154         *vpp = NULL;
 155         while (1) {
 156                 rw_wlock(&vfs_hash_lock);
 157                 LIST_FOREACH(vp2,
 158                     vfs_hash_bucket(vp->v_mount, hash), v_hashlist) {
 159                         if (vp2->v_hash != hash)
 160                                 continue;
 161                         if (vp2->v_mount != vp->v_mount)
 162                                 continue;
 163                         if (fn != NULL && fn(vp2, arg))
 164                                 continue;
 165                         vhold(vp2);
 166                         rw_wunlock(&vfs_hash_lock);
 167                         error = vget(vp2, flags | LK_VNHELD, td);
 168                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
 169                                 break;
 170                         rw_wlock(&vfs_hash_lock);
 171                         LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
 172                         rw_wunlock(&vfs_hash_lock);
 173                         vput(vp);
 174                         if (!error)
 175                                 *vpp = vp2;
 176                         return (error);
 177                 }
 178                 if (vp2 == NULL)
 179                         break;
 180
 181         }
 182         vp->v_hash = hash;
 183         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
 184         rw_wunlock(&vfs_hash_lock);
 185         return (0);
 186 }
 187
 188 void
 189 vfs_hash_rehash(struct vnode *vp, u_int hash)
 190 {
 191
 192         rw_wlock(&vfs_hash_lock);
 193         LIST_REMOVE(vp, v_hashlist);
 194         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
 195         vp->v_hash = hash;
 196         rw_wunlock(&vfs_hash_lock);
 197 }
 198
 199 void
 200 vfs_hash_changesize(int newmaxvnodes)
 201 {
 202         struct vfs_hash_head *vfs_hash_newtbl, *vfs_hash_oldtbl;
 203         u_long vfs_hash_newmask, vfs_hash_oldmask;
 204         struct vnode *vp;
 205         int i;
 206
 207         vfs_hash_newtbl = hashinit(newmaxvnodes, M_VFS_HASH,
 208                 &vfs_hash_newmask);
 209         /* If same hash table size, nothing to do */
 210         if (vfs_hash_mask == vfs_hash_newmask) {
 211                 free(vfs_hash_newtbl, M_VFS_HASH);
 212                 return;
 213         }
 214         /*
 215          * Move everything from the old hash table to the new table.
 216          * None of the vnodes in the table can be recycled because to
 217          * do so, they have to be removed from the hash table.
 218          */
 219         rw_wlock(&vfs_hash_lock);
 220         vfs_hash_oldtbl = vfs_hash_tbl;
 221         vfs_hash_oldmask = vfs_hash_mask;
 222         vfs_hash_tbl = vfs_hash_newtbl;
 223         vfs_hash_mask = vfs_hash_newmask;
 224         for (i = 0; i <= vfs_hash_oldmask; i++) {
 225                 while ((vp = LIST_FIRST(&vfs_hash_oldtbl[i])) != NULL) {
 226                         LIST_REMOVE(vp, v_hashlist);
 227                         LIST_INSERT_HEAD(
 228                             vfs_hash_bucket(vp->v_mount, vp->v_hash),
 229                             vp, v_hashlist);
 230                 }
 231         }
 232         rw_wunlock(&vfs_hash_lock);
 233         free(vfs_hash_oldtbl, M_VFS_HASH);
 234 }