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("$FreeBSD$");
   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 }

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

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