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/10.1/sys/kern/vfs_hash.c 245406 2013-01-14 05:41:40Z kib $");
   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 u_int
   58 vfs_hash_index(struct vnode *vp)
   59 {
   60 
   61         return (vp->v_hash + vp->v_mount->mnt_hashseed);
   62 }
   63 
   64 static struct vfs_hash_head *
   65 vfs_hash_bucket(const struct mount *mp, u_int hash)
   66 {
   67 
   68         return (&vfs_hash_tbl[(hash + mp->mnt_hashseed) & vfs_hash_mask]);
   69 }
   70 
   71 int
   72 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)
   73 {
   74         struct vnode *vp;
   75         int error;
   76 
   77         while (1) {
   78                 mtx_lock(&vfs_hash_mtx);
   79                 LIST_FOREACH(vp, vfs_hash_bucket(mp, hash), v_hashlist) {
   80                         if (vp->v_hash != hash)
   81                                 continue;
   82                         if (vp->v_mount != mp)
   83                                 continue;
   84                         if (fn != NULL && fn(vp, arg))
   85                                 continue;
   86                         VI_LOCK(vp);
   87                         mtx_unlock(&vfs_hash_mtx);
   88                         error = vget(vp, flags | LK_INTERLOCK, td);
   89                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
   90                                 break;
   91                         if (error)
   92                                 return (error);
   93                         *vpp = vp;
   94                         return (0);
   95                 }
   96                 if (vp == NULL) {
   97                         mtx_unlock(&vfs_hash_mtx);
   98                         *vpp = NULL;
   99                         return (0);
  100                 }
  101         }
  102 }
  103 
  104 void
  105 vfs_hash_remove(struct vnode *vp)
  106 {
  107 
  108         mtx_lock(&vfs_hash_mtx);
  109         LIST_REMOVE(vp, v_hashlist);
  110         mtx_unlock(&vfs_hash_mtx);
  111 }
  112 
  113 int
  114 vfs_hash_insert(struct vnode *vp, u_int hash, int flags, struct thread *td, struct vnode **vpp, vfs_hash_cmp_t *fn, void *arg)
  115 {
  116         struct vnode *vp2;
  117         int error;
  118 
  119         *vpp = NULL;
  120         while (1) {
  121                 mtx_lock(&vfs_hash_mtx);
  122                 LIST_FOREACH(vp2,
  123                     vfs_hash_bucket(vp->v_mount, hash), v_hashlist) {
  124                         if (vp2->v_hash != hash)
  125                                 continue;
  126                         if (vp2->v_mount != vp->v_mount)
  127                                 continue;
  128                         if (fn != NULL && fn(vp2, arg))
  129                                 continue;
  130                         VI_LOCK(vp2);
  131                         mtx_unlock(&vfs_hash_mtx);
  132                         error = vget(vp2, flags | LK_INTERLOCK, td);
  133                         if (error == ENOENT && (flags & LK_NOWAIT) == 0)
  134                                 break;
  135                         mtx_lock(&vfs_hash_mtx);
  136                         LIST_INSERT_HEAD(&vfs_hash_side, vp, v_hashlist);
  137                         mtx_unlock(&vfs_hash_mtx);
  138                         vput(vp);
  139                         if (!error)
  140                                 *vpp = vp2;
  141                         return (error);
  142                 }
  143                 if (vp2 == NULL)
  144                         break;
  145                         
  146         }
  147         vp->v_hash = hash;
  148         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
  149         mtx_unlock(&vfs_hash_mtx);
  150         return (0);
  151 }
  152 
  153 void
  154 vfs_hash_rehash(struct vnode *vp, u_int hash)
  155 {
  156 
  157         mtx_lock(&vfs_hash_mtx);
  158         LIST_REMOVE(vp, v_hashlist);
  159         LIST_INSERT_HEAD(vfs_hash_bucket(vp->v_mount, hash), vp, v_hashlist);
  160         vp->v_hash = hash;
  161         mtx_unlock(&vfs_hash_mtx);
  162 }

Cache object: 22d85be70977db46bd3298c03b8957f0


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