The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    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: releng/7.3/sys/kern/vfs_hash.c 180695 2008-07-22 14:27:47Z rwatson $");
   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/vnode.h>
   37 
   38 static MALLOC_DEFINE(M_VFS_HASH, "vfs_hash", "VFS hash table");
   39 
   40 static LIST_HEAD(vfs_hash_head, vnode)  *vfs_hash_tbl;
   41 static LIST_HEAD(,vnode)                vfs_hash_side;
   42 static u_long                           vfs_hash_mask;
   43 static struct mtx                       vfs_hash_mtx;
   44 
   45 static void
   46 vfs_hashinit(void *dummy __unused)
   47 {
   48 
   49         vfs_hash_tbl = hashinit(desiredvnodes, M_VFS_HASH, &vfs_hash_mask);
   50         mtx_init(&vfs_hash_mtx, "vfs hash", NULL, MTX_DEF);
   51         LIST_INIT(&vfs_hash_side);
   52 }
   53 
   54 /* Must be SI_ORDER_SECOND so desiredvnodes is available */
   55 SYSINIT(vfs_hash, SI_SUB_VFS, SI_ORDER_SECOND, vfs_hashinit, NULL);
   56 
   57 static struct vfs_hash_head *
   58 vfs_hash_index(const struct mount *mp, u_int hash)
   59 {
   60 
   61         return(&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
   62 }
   63 
   64 int
   65 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)
   66 {
   67         struct vnode *vp;
   68         int error;
   69 
   70         while (1) {
   71                 mtx_lock(&vfs_hash_mtx);
   72                 LIST_FOREACH(vp, vfs_hash_index(mp, hash), v_hashlist) {
   73                         if (vp->v_hash != hash)
   74                                 continue;
   75                         if (vp->v_mount != mp)
   76                                 continue;
   77                         if (fn != NULL && fn(vp, arg))
   78                                 continue;
   79                         VI_LOCK(vp);
   80                         mtx_unlock(&vfs_hash_mtx);
   81                         error = vget(vp, flags | LK_INTERLOCK, td);
   82                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
   83                                 break;
   84                         if (error)
   85                                 return (error);
   86                         *vpp = vp;
   87                         return (0);
   88                 }
   89                 if (vp == NULL) {
   90                         mtx_unlock(&vfs_hash_mtx);
   91                         *vpp = NULL;
   92                         return (0);
   93                 }
   94         }
   95 }
   96 
   97 void
   98 vfs_hash_remove(struct vnode *vp)
   99 {
  100 
  101         mtx_lock(&vfs_hash_mtx);
  102         LIST_REMOVE(vp, v_hashlist);
  103         mtx_unlock(&vfs_hash_mtx);
  104 }
  105 
  106 int
  107 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
  108 {
  109         struct vnode *vp2;
  110         int error;
  111 
  112         *vpp = NULL;
  113         while (1) {
  114                 mtx_lock(&vfs_hash_mtx);
  115                 LIST_FOREACH(vp2,
  116                     vfs_hash_index(vp->v_mount, hash), v_hashlist) {
  117                         if (vp2->v_hash != hash)
  118                                 continue;
  119                         if (vp2->v_mount != vp->v_mount)
  120                                 continue;
  121                         if (fn != NULL && fn(vp2, arg))
  122                                 continue;
  123                         VI_LOCK(vp2);
  124                         mtx_unlock(&vfs_hash_mtx);
  125                         error = vget(vp2, flags | LK_INTERLOCK, td);
  126                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
  127                                 break;
  128                         mtx_lock(&vfs_hash_mtx);
  129                         LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
  130                         mtx_unlock(&vfs_hash_mtx);
  131                         vput(vp);
  132                         if (!error)
  133                                 *vpp = vp2;
  134                         return (error);
  135                 }
  136                 if (vp2 == NULL)
  137                         break;
  138                         
  139         }
  140         vp->v_hash = hash;
  141         LIST_INSERT_HEAD(vfs_hash_index(vp->v_mount, hash), vp, v_hashlist);
  142         mtx_unlock(&vfs_hash_mtx);
  143         return (0);
  144 }
  145 
  146 void
  147 vfs_hash_rehash(struct vnode *vp, u_int hash)
  148 {
  149 
  150         mtx_lock(&vfs_hash_mtx);
  151         LIST_REMOVE(vp, v_hashlist);
  152         LIST_INSERT_HEAD(vfs_hash_index(vp->v_mount, hash), vp, v_hashlist);
  153         vp->v_hash = hash;
  154         mtx_unlock(&vfs_hash_mtx);
  155 }

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