pseudofs_vncache.c

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    1 /*-
    2  * Copyright (c) 2001 Dag-Erling Coïdan Smørgrav
    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  *    in this position and unchanged.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. The name of the author may not be used to endorse or promote products
   15  *    derived from this software without specific prior written permission.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   18  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   19  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   20  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   21  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   22  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD$");
   31 
   32 #include "opt_pseudofs.h"
   33 
   34 #include <sys/param.h>
   35 #include <sys/kernel.h>
   36 #include <sys/systm.h>
   37 #include <sys/eventhandler.h>
   38 #include <sys/lock.h>
   39 #include <sys/malloc.h>
   40 #include <sys/mutex.h>
   41 #include <sys/proc.h>
   42 #include <sys/sysctl.h>
   43 #include <sys/vnode.h>
   44 
   45 #include <fs/pseudofs/pseudofs.h>
   46 #include <fs/pseudofs/pseudofs_internal.h>
   47 
   48 static MALLOC_DEFINE(M_PFSVNCACHE, "pfs_vncache", "pseudofs vnode cache");
   49 
   50 static struct mtx pfs_vncache_mutex;
   51 static struct pfs_vdata *pfs_vncache;
   52 static eventhandler_tag pfs_exit_tag;
   53 static void pfs_exit(void *arg, struct proc *p);
   54 static void pfs_purge_locked(struct pfs_node *pn, bool force);
   55 
   56 static SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW, 0,
   57     "pseudofs vnode cache");
   58 
   59 static int pfs_vncache_entries;
   60 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, entries, CTLFLAG_RD,
   61     &pfs_vncache_entries, 0,
   62     "number of entries in the vnode cache");
   63 
   64 static int pfs_vncache_maxentries;
   65 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, maxentries, CTLFLAG_RD,
   66     &pfs_vncache_maxentries, 0,
   67     "highest number of entries in the vnode cache");
   68 
   69 static int pfs_vncache_hits;
   70 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, hits, CTLFLAG_RD,
   71     &pfs_vncache_hits, 0,
   72     "number of cache hits since initialization");
   73 
   74 static int pfs_vncache_misses;
   75 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, misses, CTLFLAG_RD,
   76     &pfs_vncache_misses, 0,
   77     "number of cache misses since initialization");
   78 
   79 extern struct vop_vector pfs_vnodeops;  /* XXX -> .h file */
   80 
   81 /*
   82  * Initialize vnode cache
   83  */
   84 void
   85 pfs_vncache_load(void)
   86 {
   87 
   88         mtx_init(&pfs_vncache_mutex, "pfs_vncache", NULL, MTX_DEF);
   89         pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL,
   90             EVENTHANDLER_PRI_ANY);
   91 }
   92 
   93 /*
   94  * Tear down vnode cache
   95  */
   96 void
   97 pfs_vncache_unload(void)
   98 {
   99 
  100         EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag);
  101         mtx_lock(&pfs_vncache_mutex);
  102         pfs_purge_locked(NULL, true);
  103         mtx_unlock(&pfs_vncache_mutex);
  104         KASSERT(pfs_vncache_entries == 0,
  105             ("%d vncache entries remaining", pfs_vncache_entries));
  106         mtx_destroy(&pfs_vncache_mutex);
  107 }
  108 
  109 /*
  110  * Allocate a vnode
  111  */
  112 int
  113 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp,
  114                   struct pfs_node *pn, pid_t pid)
  115 {
  116         struct pfs_vdata *pvd, *pvd2;
  117         struct vnode *vp;
  118         int error;
  119 
  120         /*
  121          * See if the vnode is in the cache.
  122          * XXX linear search is not very efficient.
  123          */
  124 retry:
  125         mtx_lock(&pfs_vncache_mutex);
  126         for (pvd = pfs_vncache; pvd; pvd = pvd->pvd_next) {
  127                 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid &&
  128                     pvd->pvd_vnode->v_mount == mp) {
  129                         vp = pvd->pvd_vnode;
  130                         VI_LOCK(vp);
  131                         mtx_unlock(&pfs_vncache_mutex);
  132                         if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, curthread) == 0) {
  133                                 ++pfs_vncache_hits;
  134                                 *vpp = vp;
  135                                 /*
  136                                  * Some callers cache_enter(vp) later, so
  137                                  * we have to make sure it's not in the
  138                                  * VFS cache so it doesn't get entered
  139                                  * twice.  A better solution would be to
  140                                  * make pfs_vncache_alloc() responsible
  141                                  * for entering the vnode in the VFS
  142                                  * cache.
  143                                  */
  144                                 cache_purge(vp);
  145                                 return (0);
  146                         }
  147                         goto retry;
  148                 }
  149         }
  150         mtx_unlock(&pfs_vncache_mutex);
  151 
  152         /* nope, get a new one */
  153         pvd = malloc(sizeof *pvd, M_PFSVNCACHE, M_WAITOK);
  154         pvd->pvd_next = pvd->pvd_prev = NULL;
  155         error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp);
  156         if (error) {
  157                 free(pvd, M_PFSVNCACHE);
  158                 return (error);
  159         }
  160         pvd->pvd_pn = pn;
  161         pvd->pvd_pid = pid;
  162         (*vpp)->v_data = pvd;
  163         switch (pn->pn_type) {
  164         case pfstype_root:
  165                 (*vpp)->v_vflag = VV_ROOT;
  166 #if 0
  167                 printf("root vnode allocated\n");
  168 #endif
  169                 /* fall through */
  170         case pfstype_dir:
  171         case pfstype_this:
  172         case pfstype_parent:
  173         case pfstype_procdir:
  174                 (*vpp)->v_type = VDIR;
  175                 break;
  176         case pfstype_file:
  177                 (*vpp)->v_type = VREG;
  178                 break;
  179         case pfstype_symlink:
  180                 (*vpp)->v_type = VLNK;
  181                 break;
  182         case pfstype_none:
  183                 KASSERT(0, ("pfs_vncache_alloc called for null node\n"));
  184         default:
  185                 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type);
  186         }
  187         /*
  188          * Propagate flag through to vnode so users know it can change
  189          * if the process changes (i.e. execve)
  190          */
  191         if ((pn->pn_flags & PFS_PROCDEP) != 0)
  192                 (*vpp)->v_vflag |= VV_PROCDEP;
  193         pvd->pvd_vnode = *vpp;
  194         vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY);
  195         VN_LOCK_AREC(*vpp);
  196         error = insmntque(*vpp, mp);
  197         if (error != 0) {
  198                 free(pvd, M_PFSVNCACHE);
  199                 *vpp = NULLVP;
  200                 return (error);
  201         }
  202 retry2:
  203         mtx_lock(&pfs_vncache_mutex);
  204         /*
  205          * Other thread may race with us, creating the entry we are
  206          * going to insert into the cache. Recheck after
  207          * pfs_vncache_mutex is reacquired.
  208          */
  209         for (pvd2 = pfs_vncache; pvd2; pvd2 = pvd2->pvd_next) {
  210                 if (pvd2->pvd_pn == pn && pvd2->pvd_pid == pid &&
  211                     pvd2->pvd_vnode->v_mount == mp) {
  212                         vp = pvd2->pvd_vnode;
  213                         VI_LOCK(vp);
  214                         mtx_unlock(&pfs_vncache_mutex);
  215                         if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, curthread) == 0) {
  216                                 ++pfs_vncache_hits;
  217                                 vgone(*vpp);
  218                                 vput(*vpp);
  219                                 *vpp = vp;
  220                                 cache_purge(vp);
  221                                 return (0);
  222                         }
  223                         goto retry2;
  224                 }
  225         }
  226         ++pfs_vncache_misses;
  227         if (++pfs_vncache_entries > pfs_vncache_maxentries)
  228                 pfs_vncache_maxentries = pfs_vncache_entries;
  229         pvd->pvd_prev = NULL;
  230         pvd->pvd_next = pfs_vncache;
  231         if (pvd->pvd_next)
  232                 pvd->pvd_next->pvd_prev = pvd;
  233         pfs_vncache = pvd;
  234         mtx_unlock(&pfs_vncache_mutex);
  235         return (0);
  236 }
  237 
  238 /*
  239  * Free a vnode
  240  */
  241 int
  242 pfs_vncache_free(struct vnode *vp)
  243 {
  244         struct pfs_vdata *pvd;
  245 
  246         mtx_lock(&pfs_vncache_mutex);
  247         pvd = (struct pfs_vdata *)vp->v_data;
  248         KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n"));
  249         if (pvd->pvd_next)
  250                 pvd->pvd_next->pvd_prev = pvd->pvd_prev;
  251         if (pvd->pvd_prev) {
  252                 pvd->pvd_prev->pvd_next = pvd->pvd_next;
  253                 --pfs_vncache_entries;
  254         } else if (pfs_vncache == pvd) {
  255                 pfs_vncache = pvd->pvd_next;
  256                 --pfs_vncache_entries;
  257         }
  258         mtx_unlock(&pfs_vncache_mutex);
  259 
  260         free(pvd, M_PFSVNCACHE);
  261         vp->v_data = NULL;
  262         return (0);
  263 }
  264 
  265 /*
  266  * Purge the cache of dead entries
  267  *
  268  * This is extremely inefficient due to the fact that vgone() not only
  269  * indirectly modifies the vnode cache, but may also sleep.  We can
  270  * neither hold pfs_vncache_mutex across a vgone() call, nor make any
  271  * assumptions about the state of the cache after vgone() returns.  In
  272  * consequence, we must start over after every vgone() call, and keep
  273  * trying until we manage to traverse the entire cache.
  274  *
  275  * The only way to improve this situation is to change the data structure
  276  * used to implement the cache.
  277  */
  278 static void
  279 pfs_purge_locked(struct pfs_node *pn, bool force)
  280 {
  281         struct pfs_vdata *pvd;
  282         struct vnode *vnp;
  283 
  284         mtx_assert(&pfs_vncache_mutex, MA_OWNED);
  285         pvd = pfs_vncache;
  286         while (pvd != NULL) {
  287                 if (force || pvd->pvd_dead ||
  288                     (pn != NULL && pvd->pvd_pn == pn)) {
  289                         vnp = pvd->pvd_vnode;
  290                         vhold(vnp);
  291                         mtx_unlock(&pfs_vncache_mutex);
  292                         VOP_LOCK(vnp, LK_EXCLUSIVE);
  293                         vgone(vnp);
  294                         VOP_UNLOCK(vnp, 0);
  295                         mtx_lock(&pfs_vncache_mutex);
  296                         vdrop(vnp);
  297                         pvd = pfs_vncache;
  298                 } else {
  299                         pvd = pvd->pvd_next;
  300                 }
  301         }
  302 }
  303 
  304 void
  305 pfs_purge(struct pfs_node *pn)
  306 {
  307 
  308         mtx_lock(&pfs_vncache_mutex);
  309         pfs_purge_locked(pn, false);
  310         mtx_unlock(&pfs_vncache_mutex);
  311 }
  312 
  313 /*
  314  * Free all vnodes associated with a defunct process
  315  */
  316 static void
  317 pfs_exit(void *arg, struct proc *p)
  318 {
  319         struct pfs_vdata *pvd;
  320         int dead;
  321 
  322         if (pfs_vncache == NULL)
  323                 return;
  324         mtx_lock(&pfs_vncache_mutex);
  325         for (pvd = pfs_vncache, dead = 0; pvd != NULL; pvd = pvd->pvd_next)
  326                 if (pvd->pvd_pid == p->p_pid)
  327                         dead = pvd->pvd_dead = 1;
  328         if (dead)
  329                 pfs_purge_locked(NULL, false);
  330         mtx_unlock(&pfs_vncache_mutex);
  331 }
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FreeBSD/Linux Kernel Cross Reference sys/fs/pseudofs/pseudofs_vncache.c

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sys/fs/pseudofs/pseudofs_vncache.c
