vfs_hash.c

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    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: releng/12.0/sys/kern/vfs_hash.c 326271 2017-11-27 15:20:12Z pfg $");
   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 }

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FreeBSD/Linux Kernel Cross Reference sys/kern/vfs_hash.c

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sys/kern/vfs_hash.c