null_subr.c

Version: - FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10
    1 /*-
    2  * Copyright (c) 1992, 1993
    3  *      The Regents of the University of California.  All rights reserved.
    4  *
    5  * This code is derived from software donated to Berkeley by
    6  * Jan-Simon Pendry.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 4. Neither the name of the University nor the names of its contributors
   17  *    may be used to endorse or promote products derived from this software
   18  *    without specific prior written permission.
   19  *
   20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   30  * SUCH DAMAGE.
   31  *
   32  *      @(#)null_subr.c 8.7 (Berkeley) 5/14/95
   33  *
   34  * $FreeBSD$
   35  */
   36 
   37 #include <sys/param.h>
   38 #include <sys/systm.h>
   39 #include <sys/kernel.h>
   40 #include <sys/lock.h>
   41 #include <sys/mutex.h>
   42 #include <sys/malloc.h>
   43 #include <sys/mount.h>
   44 #include <sys/proc.h>
   45 #include <sys/vnode.h>
   46 
   47 #include <fs/nullfs/null.h>
   48 
   49 /*
   50  * Null layer cache:
   51  * Each cache entry holds a reference to the lower vnode
   52  * along with a pointer to the alias vnode.  When an
   53  * entry is added the lower vnode is VREF'd.  When the
   54  * alias is removed the lower vnode is vrele'd.
   55  */
   56 
   57 #define NULL_NHASH(vp) (&null_node_hashtbl[vfs_hash_index(vp) & null_hash_mask])
   58 
   59 static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
   60 static struct mtx null_hashmtx;
   61 static u_long null_hash_mask;
   62 
   63 static MALLOC_DEFINE(M_NULLFSHASH, "nullfs_hash", "NULLFS hash table");
   64 MALLOC_DEFINE(M_NULLFSNODE, "nullfs_node", "NULLFS vnode private part");
   65 
   66 static struct vnode * null_hashins(struct mount *, struct null_node *);
   67 
   68 /*
   69  * Initialise cache headers
   70  */
   71 int
   72 nullfs_init(vfsp)
   73         struct vfsconf *vfsp;
   74 {
   75 
   76         null_node_hashtbl = hashinit(desiredvnodes, M_NULLFSHASH,
   77             &null_hash_mask);
   78         mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF);
   79         return (0);
   80 }
   81 
   82 int
   83 nullfs_uninit(vfsp)
   84         struct vfsconf *vfsp;
   85 {
   86 
   87         mtx_destroy(&null_hashmtx);
   88         hashdestroy(null_node_hashtbl, M_NULLFSHASH, null_hash_mask);
   89         return (0);
   90 }
   91 
   92 /*
   93  * Return a VREF'ed alias for lower vnode if already exists, else 0.
   94  * Lower vnode should be locked on entry and will be left locked on exit.
   95  */
   96 struct vnode *
   97 null_hashget(mp, lowervp)
   98         struct mount *mp;
   99         struct vnode *lowervp;
  100 {
  101         struct null_node_hashhead *hd;
  102         struct null_node *a;
  103         struct vnode *vp;
  104 
  105         ASSERT_VOP_LOCKED(lowervp, "null_hashget");
  106 
  107         /*
  108          * Find hash base, and then search the (two-way) linked
  109          * list looking for a null_node structure which is referencing
  110          * the lower vnode.  If found, the increment the null_node
  111          * reference count (but NOT the lower vnode's VREF counter).
  112          */
  113         hd = NULL_NHASH(lowervp);
  114         mtx_lock(&null_hashmtx);
  115         LIST_FOREACH(a, hd, null_hash) {
  116                 if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
  117                         /*
  118                          * Since we have the lower node locked the nullfs
  119                          * node can not be in the process of recycling.  If
  120                          * it had been recycled before we grabed the lower
  121                          * lock it would not have been found on the hash.
  122                          */
  123                         vp = NULLTOV(a);
  124                         vref(vp);
  125                         mtx_unlock(&null_hashmtx);
  126                         return (vp);
  127                 }
  128         }
  129         mtx_unlock(&null_hashmtx);
  130         return (NULLVP);
  131 }
  132 
  133 /*
  134  * Act like null_hashget, but add passed null_node to hash if no existing
  135  * node found.
  136  */
  137 static struct vnode *
  138 null_hashins(mp, xp)
  139         struct mount *mp;
  140         struct null_node *xp;
  141 {
  142         struct null_node_hashhead *hd;
  143         struct null_node *oxp;
  144         struct vnode *ovp;
  145 
  146         hd = NULL_NHASH(xp->null_lowervp);
  147         mtx_lock(&null_hashmtx);
  148         LIST_FOREACH(oxp, hd, null_hash) {
  149                 if (oxp->null_lowervp == xp->null_lowervp &&
  150                     NULLTOV(oxp)->v_mount == mp) {
  151                         /*
  152                          * See null_hashget for a description of this
  153                          * operation.
  154                          */
  155                         ovp = NULLTOV(oxp);
  156                         vref(ovp);
  157                         mtx_unlock(&null_hashmtx);
  158                         return (ovp);
  159                 }
  160         }
  161         LIST_INSERT_HEAD(hd, xp, null_hash);
  162         mtx_unlock(&null_hashmtx);
  163         return (NULLVP);
  164 }
  165 
  166 static void
  167 null_destroy_proto(struct vnode *vp, void *xp)
  168 {
  169 
  170         lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
  171         VI_LOCK(vp);
  172         vp->v_data = NULL;
  173         vp->v_vnlock = &vp->v_lock;
  174         vp->v_op = &dead_vnodeops;
  175         VI_UNLOCK(vp);
  176         vgone(vp);
  177         vput(vp);
  178         free(xp, M_NULLFSNODE);
  179 }
  180 
  181 static void
  182 null_insmntque_dtr(struct vnode *vp, void *xp)
  183 {
  184 
  185         vput(((struct null_node *)xp)->null_lowervp);
  186         null_destroy_proto(vp, xp);
  187 }
  188 
  189 /*
  190  * Make a new or get existing nullfs node.
  191  * Vp is the alias vnode, lowervp is the lower vnode.
  192  * 
  193  * The lowervp assumed to be locked and having "spare" reference. This routine
  194  * vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
  195  * the caller's "spare" reference to created nullfs vnode.
  196  */
  197 int
  198 null_nodeget(mp, lowervp, vpp)
  199         struct mount *mp;
  200         struct vnode *lowervp;
  201         struct vnode **vpp;
  202 {
  203         struct null_node *xp;
  204         struct vnode *vp;
  205         int error;
  206 
  207         ASSERT_VOP_LOCKED(lowervp, "lowervp");
  208         KASSERT(lowervp->v_usecount >= 1, ("Unreferenced vnode %p", lowervp));
  209 
  210         /* Lookup the hash firstly. */
  211         *vpp = null_hashget(mp, lowervp);
  212         if (*vpp != NULL) {
  213                 vrele(lowervp);
  214                 return (0);
  215         }
  216 
  217         /*
  218          * The insmntque1() call below requires the exclusive lock on
  219          * the nullfs vnode.  Upgrade the lock now if hash failed to
  220          * provide ready to use vnode.
  221          */
  222         if (VOP_ISLOCKED(lowervp) != LK_EXCLUSIVE) {
  223                 KASSERT((MOUNTTONULLMOUNT(mp)->nullm_flags & NULLM_CACHE) != 0,
  224                     ("lowervp %p is not excl locked and cache is disabled",
  225                     lowervp));
  226                 vn_lock(lowervp, LK_UPGRADE | LK_RETRY);
  227                 if ((lowervp->v_iflag & VI_DOOMED) != 0) {
  228                         vput(lowervp);
  229                         return (ENOENT);
  230                 }
  231         }
  232 
  233         /*
  234          * We do not serialize vnode creation, instead we will check for
  235          * duplicates later, when adding new vnode to hash.
  236          * Note that duplicate can only appear in hash if the lowervp is
  237          * locked LK_SHARED.
  238          *
  239          * Do the MALLOC before the getnewvnode since doing so afterward
  240          * might cause a bogus v_data pointer to get dereferenced
  241          * elsewhere if MALLOC should block.
  242          */
  243         xp = malloc(sizeof(struct null_node), M_NULLFSNODE, M_WAITOK);
  244 
  245         error = getnewvnode("null", mp, &null_vnodeops, &vp);
  246         if (error) {
  247                 vput(lowervp);
  248                 free(xp, M_NULLFSNODE);
  249                 return (error);
  250         }
  251 
  252         xp->null_vnode = vp;
  253         xp->null_lowervp = lowervp;
  254         xp->null_flags = 0;
  255         vp->v_type = lowervp->v_type;
  256         vp->v_data = xp;
  257         vp->v_vnlock = lowervp->v_vnlock;
  258         error = insmntque1(vp, mp, null_insmntque_dtr, xp);
  259         if (error != 0)
  260                 return (error);
  261         /*
  262          * Atomically insert our new node into the hash or vget existing 
  263          * if someone else has beaten us to it.
  264          */
  265         *vpp = null_hashins(mp, xp);
  266         if (*vpp != NULL) {
  267                 vrele(lowervp);
  268                 null_destroy_proto(vp, xp);
  269                 return (0);
  270         }
  271         *vpp = vp;
  272 
  273         return (0);
  274 }
  275 
  276 /*
  277  * Remove node from hash.
  278  */
  279 void
  280 null_hashrem(xp)
  281         struct null_node *xp;
  282 {
  283 
  284         mtx_lock(&null_hashmtx);
  285         LIST_REMOVE(xp, null_hash);
  286         mtx_unlock(&null_hashmtx);
  287 }
  288 
  289 #ifdef DIAGNOSTIC
  290 
  291 struct vnode *
  292 null_checkvp(vp, fil, lno)
  293         struct vnode *vp;
  294         char *fil;
  295         int lno;
  296 {
  297         struct null_node *a = VTONULL(vp);
  298 
  299 #ifdef notyet
  300         /*
  301          * Can't do this check because vop_reclaim runs
  302          * with a funny vop vector.
  303          */
  304         if (vp->v_op != null_vnodeop_p) {
  305                 printf ("null_checkvp: on non-null-node\n");
  306                 panic("null_checkvp");
  307         }
  308 #endif
  309         if (a->null_lowervp == NULLVP) {
  310                 /* Should never happen */
  311                 panic("null_checkvp %p", vp);
  312         }
  313         VI_LOCK_FLAGS(a->null_lowervp, MTX_DUPOK);
  314         if (a->null_lowervp->v_usecount < 1)
  315                 panic ("null with unref'ed lowervp, vp %p lvp %p",
  316                     vp, a->null_lowervp);
  317         VI_UNLOCK(a->null_lowervp);
  318 #ifdef notyet
  319         printf("null %x/%d -> %x/%d [%s, %d]\n",
  320                 NULLTOV(a), vrefcnt(NULLTOV(a)),
  321                 a->null_lowervp, vrefcnt(a->null_lowervp),
  322                 fil, lno);
  323 #endif
  324         return (a->null_lowervp);
  325 }
  326 #endif
Cache object: 62a90a64cef7e8074f34770945518853
[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]
This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.
FreeBSD/Linux Kernel Cross Reference sys/fs/nullfs/null_subr.c

FreeBSD/Linux Kernel Cross Reference
sys/fs/nullfs/null_subr.c
