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/fs/pseudofs/pseudofs_vncache.c

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    1 /*-
    2  * Copyright (c) 2001 Dag-Erling Co´dan Sm°rgrav
    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: releng/6.0/sys/fs/pseudofs/pseudofs_vncache.c 147809 2005-07-07 07:33:10Z jeff $");
   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 
   55 SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW, 0,
   56     "pseudofs vnode cache");
   57 
   58 static int pfs_vncache_entries;
   59 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, entries, CTLFLAG_RD,
   60     &pfs_vncache_entries, 0,
   61     "number of entries in the vnode cache");
   62 
   63 static int pfs_vncache_maxentries;
   64 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, maxentries, CTLFLAG_RD,
   65     &pfs_vncache_maxentries, 0,
   66     "highest number of entries in the vnode cache");
   67 
   68 static int pfs_vncache_hits;
   69 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, hits, CTLFLAG_RD,
   70     &pfs_vncache_hits, 0,
   71     "number of cache hits since initialization");
   72 
   73 static int pfs_vncache_misses;
   74 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, misses, CTLFLAG_RD,
   75     &pfs_vncache_misses, 0,
   76     "number of cache misses since initialization");
   77 
   78 extern struct vop_vector pfs_vnodeops;  /* XXX -> .h file */
   79 
   80 /*
   81  * Initialize vnode cache
   82  */
   83 void
   84 pfs_vncache_load(void)
   85 {
   86         mtx_init(&pfs_vncache_mutex, "pseudofs_vncache", NULL, MTX_DEF);
   87         pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL,
   88             EVENTHANDLER_PRI_ANY);
   89 }
   90 
   91 /*
   92  * Tear down vnode cache
   93  */
   94 void
   95 pfs_vncache_unload(void)
   96 {
   97         EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag);
   98         if (pfs_vncache_entries != 0)
   99                 printf("pfs_vncache_unload(): %d entries remaining\n",
  100                     pfs_vncache_entries);
  101         mtx_destroy(&pfs_vncache_mutex);
  102 }
  103 
  104 /*
  105  * Allocate a vnode
  106  */
  107 int
  108 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp,
  109                   struct pfs_node *pn, pid_t pid)
  110 {
  111         struct pfs_vdata *pvd;
  112         int error;
  113 
  114         /*
  115          * See if the vnode is in the cache.
  116          * XXX linear search is not very efficient.
  117          */
  118         mtx_lock(&pfs_vncache_mutex);
  119         for (pvd = pfs_vncache; pvd; pvd = pvd->pvd_next) {
  120                 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid &&
  121                     pvd->pvd_vnode->v_mount == mp) {
  122                         if (vget(pvd->pvd_vnode, 0, curthread) == 0) {
  123                                 ++pfs_vncache_hits;
  124                                 *vpp = pvd->pvd_vnode;
  125                                 mtx_unlock(&pfs_vncache_mutex);
  126                                 /* XXX see comment at top of pfs_lookup() */
  127                                 cache_purge(*vpp);
  128                                 vn_lock(*vpp, LK_RETRY | LK_EXCLUSIVE,
  129                                     curthread);
  130                                 return (0);
  131                         }
  132                         /* XXX if this can happen, we're in trouble */
  133                         break;
  134                 }
  135         }
  136         mtx_unlock(&pfs_vncache_mutex);
  137         ++pfs_vncache_misses;
  138 
  139         /* nope, get a new one */
  140         MALLOC(pvd, struct pfs_vdata *, sizeof *pvd, M_PFSVNCACHE, M_WAITOK);
  141         if (++pfs_vncache_entries > pfs_vncache_maxentries)
  142                 pfs_vncache_maxentries = pfs_vncache_entries;
  143         error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp);
  144         if (error) {
  145                 FREE(pvd, M_PFSVNCACHE);
  146                 return (error);
  147         }
  148         pvd->pvd_pn = pn;
  149         pvd->pvd_pid = pid;
  150         (*vpp)->v_data = pvd;
  151         switch (pn->pn_type) {
  152         case pfstype_root:
  153                 (*vpp)->v_vflag = VV_ROOT;
  154 #if 0
  155                 printf("root vnode allocated\n");
  156 #endif
  157                 /* fall through */
  158         case pfstype_dir:
  159         case pfstype_this:
  160         case pfstype_parent:
  161         case pfstype_procdir:
  162                 (*vpp)->v_type = VDIR;
  163                 break;
  164         case pfstype_file:
  165                 (*vpp)->v_type = VREG;
  166                 break;
  167         case pfstype_symlink:
  168                 (*vpp)->v_type = VLNK;
  169                 break;
  170         case pfstype_none:
  171                 KASSERT(0, ("pfs_vncache_alloc called for null node\n"));
  172         default:
  173                 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type);
  174         }
  175         /*
  176          * Propagate flag through to vnode so users know it can change
  177          * if the process changes (i.e. execve)
  178          */
  179         if ((pn->pn_flags & PFS_PROCDEP) != 0)
  180                 (*vpp)->v_vflag |= VV_PROCDEP;
  181         pvd->pvd_vnode = *vpp;
  182         mtx_lock(&pfs_vncache_mutex);
  183         pvd->pvd_prev = NULL;
  184         pvd->pvd_next = pfs_vncache;
  185         if (pvd->pvd_next)
  186                 pvd->pvd_next->pvd_prev = pvd;
  187         pfs_vncache = pvd;
  188         mtx_unlock(&pfs_vncache_mutex);
  189         (*vpp)->v_vnlock->lk_flags |= LK_CANRECURSE;
  190         vn_lock(*vpp, LK_RETRY | LK_EXCLUSIVE, curthread);
  191         return (0);
  192 }
  193 
  194 /*
  195  * Free a vnode
  196  */
  197 int
  198 pfs_vncache_free(struct vnode *vp)
  199 {
  200         struct pfs_vdata *pvd;
  201 
  202         mtx_lock(&pfs_vncache_mutex);
  203         pvd = (struct pfs_vdata *)vp->v_data;
  204         KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n"));
  205         if (pvd->pvd_next)
  206                 pvd->pvd_next->pvd_prev = pvd->pvd_prev;
  207         if (pvd->pvd_prev)
  208                 pvd->pvd_prev->pvd_next = pvd->pvd_next;
  209         else
  210                 pfs_vncache = pvd->pvd_next;
  211         mtx_unlock(&pfs_vncache_mutex);
  212 
  213         --pfs_vncache_entries;
  214         FREE(pvd, M_PFSVNCACHE);
  215         vp->v_data = NULL;
  216         return (0);
  217 }
  218 
  219 /*
  220  * Free all vnodes associated with a defunct process
  221  *
  222  * XXXRW: It is unfortunate that pfs_exit() always acquires and releases two
  223  * mutexes (one of which is Giant) for every process exit, even if procfs
  224  * isn't mounted.
  225  */
  226 static void
  227 pfs_exit(void *arg, struct proc *p)
  228 {
  229         struct pfs_vdata *pvd;
  230         struct vnode *vnp;
  231 
  232         if (pfs_vncache == NULL)
  233                 return;
  234         mtx_lock(&Giant);
  235         /*
  236          * This is extremely inefficient due to the fact that vgone() not
  237          * only indirectly modifies the vnode cache, but may also sleep.
  238          * We can neither hold pfs_vncache_mutex across a vgone() call,
  239          * nor make any assumptions about the state of the cache after
  240          * vgone() returns.  In consequence, we must start over after
  241          * every vgone() call, and keep trying until we manage to traverse
  242          * the entire cache.
  243          *
  244          * The only way to improve this situation is to change the data
  245          * structure used to implement the cache.  An obvious choice in
  246          * this particular case would be a BST sorted by PID.
  247          */
  248         mtx_lock(&pfs_vncache_mutex);
  249         pvd = pfs_vncache;
  250         while (pvd != NULL) {
  251                 if (pvd->pvd_pid == p->p_pid) {
  252                         vnp = pvd->pvd_vnode;
  253                         vhold(vnp);
  254                         mtx_unlock(&pfs_vncache_mutex);
  255                         VOP_LOCK(vnp, LK_EXCLUSIVE, curthread);
  256                         vgone(vnp);
  257                         VOP_UNLOCK(vnp, 0, curthread);
  258                         vdrop(vnp);
  259                         mtx_lock(&pfs_vncache_mutex);
  260                         pvd = pfs_vncache;
  261                 } else {
  262                         pvd = pvd->pvd_next;
  263                 }
  264         }
  265         mtx_unlock(&pfs_vncache_mutex);
  266         mtx_unlock(&Giant);
  267 }
  268 
  269 /*
  270  * Disable a pseudofs node, and free all vnodes associated with it
  271  */
  272 int
  273 pfs_disable(struct pfs_node *pn)
  274 {
  275         struct pfs_vdata *pvd;
  276         struct vnode *vnp;
  277 
  278         if (pn->pn_flags & PFS_DISABLED)
  279                 return (0);
  280         pn->pn_flags |= PFS_DISABLED;
  281         /* XXX see comment above nearly identical code in pfs_exit() */
  282         mtx_lock(&pfs_vncache_mutex);
  283         pvd = pfs_vncache;
  284         while (pvd != NULL) {
  285                 if (pvd->pvd_pn == pn) {
  286                         vnp = pvd->pvd_vnode;
  287                         vhold(vnp);
  288                         mtx_unlock(&pfs_vncache_mutex);
  289                         VOP_LOCK(vnp, LK_EXCLUSIVE, curthread);
  290                         vgone(vnp);
  291                         VOP_UNLOCK(vnp, 0, curthread);
  292                         vdrop(vnp);
  293                         mtx_lock(&pfs_vncache_mutex);
  294                         pvd = pfs_vncache;
  295                 } else {
  296                         pvd = pvd->pvd_next;
  297                 }
  298         }
  299         mtx_unlock(&pfs_vncache_mutex);
  300         return (0);
  301 }
  302 
  303 /*
  304  * Re-enable a disabled pseudofs node
  305  */
  306 int
  307 pfs_enable(struct pfs_node *pn)
  308 {
  309         pn->pn_flags &= ~PFS_DISABLED;
  310         return (0);
  311 }

Cache object: dd61d6bd278eec7a816039fd70111f35


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