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 __exclusive_cache_line 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         enum vgetstate vs;
  80         int error;
  81
  82         while (1) {
  83                 rw_rlock(&vfs_hash_lock);
  84                 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
  85                         if (vp->v_hash != hash)
  86                                 continue;
  87                         if (vp->v_mount != mp)
  88                                 continue;
  89                         if (fn != NULL && fn(vp, arg))
  90                                 continue;
  91                         vs = vget_prep(vp);
  92                         rw_runlock(&vfs_hash_lock);
  93                         error = vget_finish(vp, flags, vs);
  94                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
  95                                 break;
  96                         if (error)
  97                                 return (error);
  98                         *vpp = vp;
  99                         return (0);
 100                 }
 101                 if (vp == NULL) {
 102                         rw_runlock(&vfs_hash_lock);
 103                         *vpp = NULL;
 104                         return (0);
 105                 }
 106         }
 107 }
 108
 109 void
 110 vfs_hash_ref(const struct mount *mp, u_int hash, struct thread *td,
 111     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
 112 {
 113         struct vnode *vp;
 114
 115         while (1) {
 116                 rw_rlock(&vfs_hash_lock);
 117                 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
 118                         if (vp->v_hash != hash)
 119                                 continue;
 120                         if (vp->v_mount != mp)
 121                                 continue;
 122                         if (fn != NULL && fn(vp, arg))
 123                                 continue;
 124                         vhold(vp);
 125                         rw_runlock(&vfs_hash_lock);
 126                         vref(vp);
 127                         vdrop(vp);
 128                         *vpp = vp;
 129                         return;
 130                 }
 131                 if (vp == NULL) {
 132                         rw_runlock(&vfs_hash_lock);
 133                         *vpp = NULL;
 134                         return;
 135                 }
 136         }
 137 }
 138
 139 void
 140 vfs_hash_remove(struct vnode *vp)
 141 {
 142
 143         rw_wlock(&vfs_hash_lock);
 144         LIST_REMOVE(vp, v_hashlist);
 145         rw_wunlock(&vfs_hash_lock);
 146 }
 147
 148 int
 149 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td,
 150     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
 151 {
 152         struct vnode *vp2;
 153         enum vgetstate vs;
 154         int error;
 155
 156         *vpp = NULL;
 157         while (1) {
 158                 rw_wlock(&vfs_hash_lock);
 159                 LIST_FOREACH(vp2,
 160                     vfs_hash_bucket(vp->v_mount, hash), v_hashlist) {
 161                         if (vp2->v_hash != hash)
 162                                 continue;
 163                         if (vp2->v_mount != vp->v_mount)
 164                                 continue;
 165                         if (fn != NULL && fn(vp2, arg))
 166                                 continue;
 167                         vs = vget_prep(vp2);
 168                         rw_wunlock(&vfs_hash_lock);
 169                         error = vget_finish(vp2, flags, vs);
 170                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
 171                                 break;
 172                         rw_wlock(&vfs_hash_lock);
 173                         LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
 174                         rw_wunlock(&vfs_hash_lock);
 175                         vgone(vp);
 176                         vput(vp);
 177                         if (!error)
 178                                 *vpp = vp2;
 179                         return (error);
 180                 }
 181                 if (vp2 == NULL)
 182                         break;
 183         }
 184         vp->v_hash = hash;
 185         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
 186         rw_wunlock(&vfs_hash_lock);
 187         return (0);
 188 }
 189
 190 void
 191 vfs_hash_rehash(struct vnode *vp, u_int hash)
 192 {
 193
 194         rw_wlock(&vfs_hash_lock);
 195         LIST_REMOVE(vp, v_hashlist);
 196         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
 197         vp->v_hash = hash;
 198         rw_wunlock(&vfs_hash_lock);
 199 }
 200
 201 void
 202 vfs_hash_changesize(u_long newmaxvnodes)
 203 {
 204         struct vfs_hash_head *vfs_hash_newtbl, *vfs_hash_oldtbl;
 205         u_long vfs_hash_newmask, vfs_hash_oldmask;
 206         struct vnode *vp;
 207         int i;
 208
 209         vfs_hash_newtbl = hashinit(newmaxvnodes, M_VFS_HASH,
 210                 &vfs_hash_newmask);
 211         /* If same hash table size, nothing to do */
 212         if (vfs_hash_mask == vfs_hash_newmask) {
 213                 free(vfs_hash_newtbl, M_VFS_HASH);
 214                 return;
 215         }
 216         /*
 217          * Move everything from the old hash table to the new table.
 218          * None of the vnodes in the table can be recycled because to
 219          * do so, they have to be removed from the hash table.
 220          */
 221         rw_wlock(&vfs_hash_lock);
 222         vfs_hash_oldtbl = vfs_hash_tbl;
 223         vfs_hash_oldmask = vfs_hash_mask;
 224         vfs_hash_tbl = vfs_hash_newtbl;
 225         vfs_hash_mask = vfs_hash_newmask;
 226         for (i = 0; i <= vfs_hash_oldmask; i++) {
 227                 while ((vp = LIST_FIRST(&vfs_hash_oldtbl[i])) != NULL) {
 228                         LIST_REMOVE(vp, v_hashlist);
 229                         LIST_INSERT_HEAD(
 230                             vfs_hash_bucket(vp->v_mount, vp->v_hash),
 231                             vp, v_hashlist);
 232                 }
 233         }
 234         rw_wunlock(&vfs_hash_lock);
 235         free(vfs_hash_oldtbl, M_VFS_HASH);
 236 }