null_subr.c

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

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