sys/kern/vfs_hash.c

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