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 != 0)
   97                                 return (error);
   98                         if (vp->v_hash != hash ||
   99                             (fn != NULL && fn(vp, arg))) {
  100                                 vput(vp);
  101                                 /* Restart the bucket walk. */
  102                                 break;
  103                         }
  104                         *vpp = vp;
  105                         return (0);
  106                 }
  107                 if (vp == NULL) {
  108                         rw_runlock(&vfs_hash_lock);
  109                         *vpp = NULL;
  110                         return (0);
  111                 }
  112         }
  113 }
  114 
  115 void
  116 vfs_hash_ref(const struct mount *mp, u_int hash, struct thread *td,
  117     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
  118 {
  119         struct vnode *vp;
  120 
  121         while (1) {
  122                 rw_rlock(&vfs_hash_lock);
  123                 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
  124                         if (vp->v_hash != hash)
  125                                 continue;
  126                         if (vp->v_mount != mp)
  127                                 continue;
  128                         if (fn != NULL && fn(vp, arg))
  129                                 continue;
  130                         vhold(vp);
  131                         rw_runlock(&vfs_hash_lock);
  132                         vref(vp);
  133                         vdrop(vp);
  134                         *vpp = vp;
  135                         return;
  136                 }
  137                 if (vp == NULL) {
  138                         rw_runlock(&vfs_hash_lock);
  139                         *vpp = NULL;
  140                         return;
  141                 }
  142         }
  143 }
  144 
  145 void
  146 vfs_hash_remove(struct vnode *vp)
  147 {
  148 
  149         rw_wlock(&vfs_hash_lock);
  150         LIST_REMOVE(vp, v_hashlist);
  151         rw_wunlock(&vfs_hash_lock);
  152 }
  153 
  154 int
  155 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td,
  156     struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
  157 {
  158         struct vnode *vp2;
  159         enum vgetstate vs;
  160         int error;
  161 
  162         *vpp = NULL;
  163         while (1) {
  164                 rw_wlock(&vfs_hash_lock);
  165                 LIST_FOREACH(vp2,
  166                     vfs_hash_bucket(vp->v_mount, hash), v_hashlist) {
  167                         if (vp2->v_hash != hash)
  168                                 continue;
  169                         if (vp2->v_mount != vp->v_mount)
  170                                 continue;
  171                         if (fn != NULL && fn(vp2, arg))
  172                                 continue;
  173                         vs = vget_prep(vp2);
  174                         rw_wunlock(&vfs_hash_lock);
  175                         error = vget_finish(vp2, flags, vs);
  176                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
  177                                 break;
  178                         rw_wlock(&vfs_hash_lock);
  179                         LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
  180                         rw_wunlock(&vfs_hash_lock);
  181                         vgone(vp);
  182                         vput(vp);
  183                         if (!error)
  184                                 *vpp = vp2;
  185                         return (error);
  186                 }
  187                 if (vp2 == NULL)
  188                         break;
  189         }
  190         vp->v_hash = hash;
  191         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
  192         rw_wunlock(&vfs_hash_lock);
  193         return (0);
  194 }
  195 
  196 void
  197 vfs_hash_rehash(struct vnode *vp, u_int hash)
  198 {
  199         ASSERT_VOP_ELOCKED(vp, "rehash requires excl lock");
  200 
  201         rw_wlock(&vfs_hash_lock);
  202         LIST_REMOVE(vp, v_hashlist);
  203         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
  204         vp->v_hash = hash;
  205         rw_wunlock(&vfs_hash_lock);
  206 }
  207 
  208 void
  209 vfs_hash_changesize(u_long newmaxvnodes)
  210 {
  211         struct vfs_hash_head *vfs_hash_newtbl, *vfs_hash_oldtbl;
  212         u_long vfs_hash_newmask, vfs_hash_oldmask;
  213         struct vnode *vp;
  214         int i;
  215 
  216         vfs_hash_newtbl = hashinit(newmaxvnodes, M_VFS_HASH,
  217                 &vfs_hash_newmask);
  218         /* If same hash table size, nothing to do */
  219         if (vfs_hash_mask == vfs_hash_newmask) {
  220                 free(vfs_hash_newtbl, M_VFS_HASH);
  221                 return;
  222         }
  223         /*
  224          * Move everything from the old hash table to the new table.
  225          * None of the vnodes in the table can be recycled because to
  226          * do so, they have to be removed from the hash table.
  227          */
  228         rw_wlock(&vfs_hash_lock);
  229         vfs_hash_oldtbl = vfs_hash_tbl;
  230         vfs_hash_oldmask = vfs_hash_mask;
  231         vfs_hash_tbl = vfs_hash_newtbl;
  232         vfs_hash_mask = vfs_hash_newmask;
  233         for (i = 0; i <= vfs_hash_oldmask; i++) {
  234                 while ((vp = LIST_FIRST(&vfs_hash_oldtbl[i])) != NULL) {
  235                         LIST_REMOVE(vp, v_hashlist);
  236                         LIST_INSERT_HEAD(
  237                             vfs_hash_bucket(vp->v_mount, vp->v_hash),
  238                             vp, v_hashlist);
  239                 }
  240         }
  241         rw_wunlock(&vfs_hash_lock);
  242         free(vfs_hash_oldtbl, M_VFS_HASH);
  243 }

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

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