sys/fs/pseudofs/pseudofs_vncache.c

   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
  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
  87         mtx_assert(&Giant, MA_OWNED);
  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         mtx_assert(&Giant, MA_OWNED);
 101         EVENTHANDLER_DEREGISTER(process_exit, pfs_exit_tag);
 102         KASSERT(pfs_vncache_entries == 0,
 103             ("%d vncache entries remaining", pfs_vncache_entries));
 104         mtx_destroy(&pfs_vncache_mutex);
 105 }
 106
 107 /*
 108  * Allocate a vnode
 109  */
 110 int
 111 pfs_vncache_alloc(struct mount *mp, struct vnode **vpp,
 112                   struct pfs_node *pn, pid_t pid)
 113 {
 114         struct pfs_vdata *pvd;
 115         struct vnode *vp;
 116         int error;
 117
 118         /*
 119          * See if the vnode is in the cache.
 120          * XXX linear search is not very efficient.
 121          */
 122 retry:
 123         mtx_lock(&pfs_vncache_mutex);
 124         for (pvd = pfs_vncache; pvd; pvd = pvd->pvd_next) {
 125                 if (pvd->pvd_pn == pn && pvd->pvd_pid == pid &&
 126                     pvd->pvd_vnode->v_mount == mp) {
 127                         vp = pvd->pvd_vnode;
 128                         VI_LOCK(vp);
 129                         mtx_unlock(&pfs_vncache_mutex);
 130                         if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, curthread) == 0) {
 131                                 ++pfs_vncache_hits;
 132                                 *vpp = vp;
 133                                 /*
 134                                  * Some callers cache_enter(vp) later, so
 135                                  * we have to make sure it's not in the
 136                                  * VFS cache so it doesn't get entered
 137                                  * twice.  A better solution would be to
 138                                  * make pfs_vncache_alloc() responsible
 139                                  * for entering the vnode in the VFS
 140                                  * cache.
 141                                  */
 142                                 cache_purge(vp);
 143                                 return (0);
 144                         }
 145                         goto retry;
 146                 }
 147         }
 148         mtx_unlock(&pfs_vncache_mutex);
 149         ++pfs_vncache_misses;
 150
 151         /* nope, get a new one */
 152         MALLOC(pvd, struct pfs_vdata *, sizeof *pvd, M_PFSVNCACHE, M_WAITOK);
 153         mtx_lock(&pfs_vncache_mutex);
 154         if (++pfs_vncache_entries > pfs_vncache_maxentries)
 155                 pfs_vncache_maxentries = pfs_vncache_entries;
 156         mtx_unlock(&pfs_vncache_mutex);
 157         error = getnewvnode("pseudofs", mp, &pfs_vnodeops, vpp);
 158         if (error) {
 159                 mtx_lock(&pfs_vncache_mutex);
 160                 --pfs_vncache_entries;
 161                 mtx_unlock(&pfs_vncache_mutex);
 162                 FREE(pvd, M_PFSVNCACHE);
 163                 return (error);
 164         }
 165         pvd->pvd_pn = pn;
 166         pvd->pvd_pid = pid;
 167         (*vpp)->v_data = pvd;
 168         switch (pn->pn_type) {
 169         case pfstype_root:
 170                 (*vpp)->v_vflag = VV_ROOT;
 171 #if 0
 172                 printf("root vnode allocated\n");
 173 #endif
 174                 /* fall through */
 175         case pfstype_dir:
 176         case pfstype_this:
 177         case pfstype_parent:
 178         case pfstype_procdir:
 179                 (*vpp)->v_type = VDIR;
 180                 break;
 181         case pfstype_file:
 182                 (*vpp)->v_type = VREG;
 183                 break;
 184         case pfstype_symlink:
 185                 (*vpp)->v_type = VLNK;
 186                 break;
 187         case pfstype_none:
 188                 KASSERT(0, ("pfs_vncache_alloc called for null node\n"));
 189         default:
 190                 panic("%s has unexpected type: %d", pn->pn_name, pn->pn_type);
 191         }
 192         /*
 193          * Propagate flag through to vnode so users know it can change
 194          * if the process changes (i.e. execve)
 195          */
 196         if ((pn->pn_flags & PFS_PROCDEP) != 0)
 197                 (*vpp)->v_vflag |= VV_PROCDEP;
 198         pvd->pvd_vnode = *vpp;
 199         VN_LOCK_AREC(*vpp);
 200         vn_lock(*vpp, LK_EXCLUSIVE | LK_RETRY);
 201         error = insmntque(*vpp, mp);
 202         if (error != 0) {
 203                 mtx_lock(&pfs_vncache_mutex);
 204                 --pfs_vncache_entries;
 205                 mtx_unlock(&pfs_vncache_mutex);
 206                 FREE(pvd, M_PFSVNCACHE);
 207                 *vpp = NULLVP;
 208                 return (error);
 209         }
 210         mtx_lock(&pfs_vncache_mutex);
 211         pvd->pvd_prev = NULL;
 212         pvd->pvd_next = pfs_vncache;
 213         if (pvd->pvd_next)
 214                 pvd->pvd_next->pvd_prev = pvd;
 215         pfs_vncache = pvd;
 216         mtx_unlock(&pfs_vncache_mutex);
 217         return (0);
 218 }
 219
 220 /*
 221  * Free a vnode
 222  */
 223 int
 224 pfs_vncache_free(struct vnode *vp)
 225 {
 226         struct pfs_vdata *pvd;
 227
 228         mtx_lock(&pfs_vncache_mutex);
 229         pvd = (struct pfs_vdata *)vp->v_data;
 230         KASSERT(pvd != NULL, ("pfs_vncache_free(): no vnode data\n"));
 231         if (pvd->pvd_next)
 232                 pvd->pvd_next->pvd_prev = pvd->pvd_prev;
 233         if (pvd->pvd_prev)
 234                 pvd->pvd_prev->pvd_next = pvd->pvd_next;
 235         else
 236                 pfs_vncache = pvd->pvd_next;
 237         --pfs_vncache_entries;
 238         mtx_unlock(&pfs_vncache_mutex);
 239
 240         FREE(pvd, M_PFSVNCACHE);
 241         vp->v_data = NULL;
 242         return (0);
 243 }
 244
 245 /*
 246  * Purge the cache of dead entries
 247  *
 248  * This is extremely inefficient due to the fact that vgone() not only
 249  * indirectly modifies the vnode cache, but may also sleep.  We can
 250  * neither hold pfs_vncache_mutex across a vgone() call, nor make any
 251  * assumptions about the state of the cache after vgone() returns.  In
 252  * consequence, we must start over after every vgone() call, and keep
 253  * trying until we manage to traverse the entire cache.
 254  *
 255  * The only way to improve this situation is to change the data structure
 256  * used to implement the cache.
 257  */
 258 void
 259 pfs_purge(struct pfs_node *pn)
 260 {
 261         struct pfs_vdata *pvd;
 262         struct vnode *vnp;
 263
 264         mtx_lock(&pfs_vncache_mutex);
 265         pvd = pfs_vncache;
 266         while (pvd != NULL) {
 267                 if (pvd->pvd_dead || (pn != NULL && pvd->pvd_pn == pn)) {
 268                         vnp = pvd->pvd_vnode;
 269                         vhold(vnp);
 270                         mtx_unlock(&pfs_vncache_mutex);
 271                         VOP_LOCK(vnp, LK_EXCLUSIVE);
 272                         vgone(vnp);
 273                         VOP_UNLOCK(vnp, 0);
 274                         vdrop(vnp);
 275                         mtx_lock(&pfs_vncache_mutex);
 276                         pvd = pfs_vncache;
 277                 } else {
 278                         pvd = pvd->pvd_next;
 279                 }
 280         }
 281         mtx_unlock(&pfs_vncache_mutex);
 282 }
 283
 284 /*
 285  * Free all vnodes associated with a defunct process
 286  *
 287  * XXXRW: It is unfortunate that pfs_exit() always acquires and releases two
 288  * mutexes (one of which is Giant) for every process exit, even if procfs
 289  * isn't mounted.
 290  */
 291 static void
 292 pfs_exit(void *arg, struct proc *p)
 293 {
 294         struct pfs_vdata *pvd;
 295         int dead;
 296
 297         if (pfs_vncache == NULL)
 298                 return;
 299         mtx_lock(&Giant);
 300         mtx_lock(&pfs_vncache_mutex);
 301         for (pvd = pfs_vncache, dead = 0; pvd != NULL; pvd = pvd->pvd_next)
 302                 if (pvd->pvd_pid == p->p_pid)
 303                         dead = pvd->pvd_dead = 1;
 304         mtx_unlock(&pfs_vncache_mutex);
 305         if (dead)
 306                 pfs_purge(NULL);
 307         mtx_unlock(&Giant);
 308 }