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  *      $FreeBSD$
   29  */
   30 
   31 #include <sys/param.h>
   32 #include <sys/kernel.h>
   33 #include <sys/systm.h>
   34 #include <sys/eventhandler.h>
   35 #include <sys/lock.h>
   36 #include <sys/malloc.h>
   37 #include <sys/mutex.h>
   38 #include <sys/proc.h>
   39 #include <sys/sysctl.h>
   40 #include <sys/vnode.h>
   41 
   42 #include <fs/pseudofs/pseudofs.h>
   43 #include <fs/pseudofs/pseudofs_internal.h>
   44 
   45 static MALLOC_DEFINE(M_PFSVNCACHE, "pfs_vncache", "pseudofs vnode cache");
   46 
   47 static struct mtx pfs_vncache_mutex;
   48 static struct pfs_vdata *pfs_vncache;
   49 static eventhandler_tag pfs_exit_tag;
   50 static void pfs_exit(void *arg, struct proc *p);
   51 
   52 SYSCTL_NODE(_vfs_pfs, OID_AUTO, vncache, CTLFLAG_RW, 0,
   53     "pseudofs vnode cache");
   54 
   55 static int pfs_vncache_entries;
   56 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, entries, CTLFLAG_RD,
   57     &pfs_vncache_entries, 0,
   58     "number of entries in the vnode cache");
   59 
   60 static int pfs_vncache_maxentries;
   61 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, maxentries, CTLFLAG_RD,
   62     &pfs_vncache_maxentries, 0,
   63     "highest number of entries in the vnode cache");
   64 
   65 static int pfs_vncache_hits;
   66 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, hits, CTLFLAG_RD,
   67     &pfs_vncache_hits, 0,
   68     "number of cache hits since initialization");
   69 
   70 static int pfs_vncache_misses;
   71 SYSCTL_INT(_vfs_pfs_vncache, OID_AUTO, misses, CTLFLAG_RD,
   72     &pfs_vncache_misses, 0,
   73     "number of cache misses since initialization");
   74 
   75 extern vop_t **pfs_vnodeop_p;
   76 
   77 /*
   78  * Initialize vnode cache
   79  */
   80 void
   81 pfs_vncache_load(void)
   82 {
   83         mtx_init(&pfs_vncache_mutex, "pseudofs_vncache", NULL, MTX_DEF);
   84         pfs_exit_tag = EVENTHANDLER_REGISTER(process_exit, pfs_exit, NULL,
   85             EVENTHANDLER_PRI_ANY);
   86 }
   87 
   88 /*
   89  * Tear down vnode cache
   90  */
   91 void
   92 pfs_vncache_unload(void)
   93 {
   94         EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag);
   95         if (pfs_vncache_entries != 0)
   96                 printf("pfs_vncache_unload(): %d entries remaining\n",
   97                     pfs_vncache_entries);
   98         mtx_destroy(&pfs_vncache_mutex);
   99 }
  100 
  101 /*
  102  * Allocate a vnode
  103  */
  104 int
  105 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp,
  106                   struct pfs_node *pn, pid_t pid)
  107 {
  108         struct pfs_vdata *pvd;
  109         int error;
  110 
  111         /*
  112          * See if the vnode is in the cache.
  113          * XXX linear search is not very efficient.
  114          */
  115         mtx_lock(&pfs_vncache_mutex);
  116         for (pvd = pfs_vncache; pvd; pvd = pvd->pvd_next) {
  117                 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid &&
  118                     pvd->pvd_vnode->v_mount == mp) {
  119                         if (vget(pvd->pvd_vnode, 0, curthread) == 0) {
  120                                 ++pfs_vncache_hits;
  121                                 *vpp = pvd->pvd_vnode;
  122                                 mtx_unlock(&pfs_vncache_mutex);
  123                                 /* XXX see comment at top of pfs_lookup() */
  124                                 cache_purge(*vpp);
  125                                 vn_lock(*vpp, LK_RETRY | LK_EXCLUSIVE,
  126                                     curthread);
  127                                 return (0);
  128                         }
  129                         /* XXX if this can happen, we're in trouble */
  130                         break;
  131                 }
  132         }
  133         mtx_unlock(&pfs_vncache_mutex);
  134         ++pfs_vncache_misses;
  135 
  136         /* nope, get a new one */
  137         MALLOC(pvd, struct pfs_vdata *, sizeof *pvd, M_PFSVNCACHE, M_WAITOK);
  138         if (++pfs_vncache_entries > pfs_vncache_maxentries)
  139                 pfs_vncache_maxentries = pfs_vncache_entries;
  140         error = getnewvnode("pseudofs", mp, pfs_vnodeop_p, vpp);
  141         if (error) {
  142                 FREE(pvd, M_PFSVNCACHE);
  143                 return (error);
  144         }
  145         pvd->pvd_pn = pn;
  146         pvd->pvd_pid = pid;
  147         (*vpp)->v_data = pvd;
  148         switch (pn->pn_type) {
  149         case pfstype_root:
  150                 (*vpp)->v_vflag = VV_ROOT;
  151 #if 0
  152                 printf("root vnode allocated\n");
  153 #endif
  154                 /* fall through */
  155         case pfstype_dir:
  156         case pfstype_this:
  157         case pfstype_parent:
  158         case pfstype_procdir:
  159                 (*vpp)->v_type = VDIR;
  160                 break;
  161         case pfstype_file:
  162                 (*vpp)->v_type = VREG;
  163                 break;
  164         case pfstype_symlink:
  165                 (*vpp)->v_type = VLNK;
  166                 break;
  167         case pfstype_none:
  168                 KASSERT(0, ("pfs_vncache_alloc called for null node\n"));
  169         default:
  170                 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type);
  171         }
  172         /*
  173          * Propagate flag through to vnode so users know it can change
  174          * if the process changes (i.e. execve)
  175          */
  176         if ((pn->pn_flags & PFS_PROCDEP) != 0)
  177                 (*vpp)->v_vflag |= VV_PROCDEP;
  178         pvd->pvd_vnode = *vpp;
  179         mtx_lock(&pfs_vncache_mutex);
  180         pvd->pvd_prev = NULL;
  181         pvd->pvd_next = pfs_vncache;
  182         if (pvd->pvd_next)
  183                 pvd->pvd_next->pvd_prev = pvd;
  184         pfs_vncache = pvd;
  185         mtx_unlock(&pfs_vncache_mutex);
  186         (*vpp)->v_vnlock->lk_flags |= LK_CANRECURSE;
  187         vn_lock(*vpp, LK_RETRY | LK_EXCLUSIVE, curthread);
  188         return (0);
  189 }
  190 
  191 /*
  192  * Free a vnode
  193  */
  194 int
  195 pfs_vncache_free(struct vnode *vp)
  196 {
  197         struct pfs_vdata *pvd;
  198 
  199         mtx_lock(&pfs_vncache_mutex);
  200         pvd = (struct pfs_vdata *)vp->v_data;
  201         KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n"));
  202         if (pvd->pvd_next)
  203                 pvd->pvd_next->pvd_prev = pvd->pvd_prev;
  204         if (pvd->pvd_prev)
  205                 pvd->pvd_prev->pvd_next = pvd->pvd_next;
  206         else
  207                 pfs_vncache = pvd->pvd_next;
  208         mtx_unlock(&pfs_vncache_mutex);
  209 
  210         --pfs_vncache_entries;
  211         FREE(pvd, M_PFSVNCACHE);
  212         vp->v_data = NULL;
  213         return (0);
  214 }
  215 
  216 /*
  217  * Free all vnodes associated with a defunct process
  218  */
  219 static void
  220 pfs_exit(void *arg, struct proc *p)
  221 {
  222         struct pfs_vdata *pvd;
  223         struct vnode *vnp;
  224 
  225         mtx_lock(&Giant);
  226         /*
  227          * This is extremely inefficient due to the fact that vgone() not
  228          * only indirectly modifies the vnode cache, but may also sleep.
  229          * We can neither hold pfs_vncache_mutex across a vgone() call,
  230          * nor make any assumptions about the state of the cache after
  231          * vgone() returns.  In consequence, we must start over after
  232          * every vgone() call, and keep trying until we manage to traverse
  233          * the entire cache.
  234          *
  235          * The only way to improve this situation is to change the data
  236          * structure used to implement the cache.  An obvious choice in
  237          * this particular case would be a BST sorted by PID.
  238          */
  239         mtx_lock(&pfs_vncache_mutex);
  240         pvd = pfs_vncache;
  241         while (pvd != NULL) {
  242                 if (pvd->pvd_pid == p->p_pid) {
  243                         vnp = pvd->pvd_vnode;
  244                         mtx_unlock(&pfs_vncache_mutex);
  245                         vgone(vnp);
  246                         mtx_lock(&pfs_vncache_mutex);
  247                         pvd = pfs_vncache;
  248                 } else {
  249                         pvd = pvd->pvd_next;
  250                 }
  251         }
  252         mtx_unlock(&pfs_vncache_mutex);
  253         mtx_unlock(&Giant);
  254 }
  255 
  256 /*
  257  * Disable a pseudofs node, and free all vnodes associated with it
  258  */
  259 int
  260 pfs_disable(struct pfs_node *pn)
  261 {
  262         struct pfs_vdata *pvd;
  263         struct vnode *vnp;
  264 
  265         if (pn->pn_flags & PFS_DISABLED)
  266                 return (0);
  267         pn->pn_flags |= PFS_DISABLED;
  268         /* XXX see comment above nearly identical code in pfs_exit() */
  269         mtx_lock(&pfs_vncache_mutex);
  270         pvd = pfs_vncache;
  271         while (pvd != NULL) {
  272                 if (pvd->pvd_pn == pn) {
  273                         vnp = pvd->pvd_vnode;
  274                         mtx_unlock(&pfs_vncache_mutex);
  275                         vgone(vnp);
  276                         mtx_lock(&pfs_vncache_mutex);
  277                         pvd = pfs_vncache;
  278                 } else {
  279                         pvd = pvd->pvd_next;
  280                 }
  281         }
  282         mtx_unlock(&pfs_vncache_mutex);
  283         return (0);
  284 }
  285 
  286 /*
  287  * Re-enable a disabled pseudofs node
  288  */
  289 int
  290 pfs_enable(struct pfs_node *pn)
  291 {
  292         pn->pn_flags &= ~PFS_DISABLED;
  293         return (0);
  294 }

Cache object: b70d7d8664a96764c3221f9ae85b00ed


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