The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/fs/pseudofs/pseudofs_fileno.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: releng/5.0/sys/fs/pseudofs/pseudofs_fileno.c 97940 2002-06-06 16:59:24Z des $
   29  */
   30 
   31 #include <sys/param.h>
   32 #include <sys/kernel.h>
   33 #include <sys/systm.h>
   34 #include <sys/lock.h>
   35 #include <sys/malloc.h>
   36 #include <sys/mutex.h>
   37 #include <sys/sysctl.h>
   38 
   39 #include <machine/limits.h>
   40 
   41 #include <fs/pseudofs/pseudofs.h>
   42 #include <fs/pseudofs/pseudofs_internal.h>
   43 
   44 static MALLOC_DEFINE(M_PFSFILENO, "pfs_fileno", "pseudofs fileno bitmap");
   45 
   46 static struct mtx pfs_fileno_mutex;
   47 
   48 #define PFS_BITMAP_SIZE 4096
   49 #define PFS_SLOT_BITS   (int)(sizeof(unsigned int) * CHAR_BIT)
   50 #define PFS_BITMAP_BITS (PFS_BITMAP_SIZE * PFS_SLOT_BITS)
   51 struct pfs_bitmap {
   52         u_int32_t                pb_offset;
   53         int                      pb_used;
   54         unsigned int             pb_bitmap[PFS_BITMAP_SIZE];
   55         struct pfs_bitmap       *pb_next;
   56 };
   57 
   58 /*
   59  * Initialization
   60  */
   61 void
   62 pfs_fileno_load(void)
   63 {
   64         mtx_init(&pfs_fileno_mutex, "pseudofs_fileno", NULL, MTX_DEF);
   65 }
   66 
   67 /*
   68  * Teardown
   69  */
   70 void
   71 pfs_fileno_unload(void)
   72 {
   73         mtx_destroy(&pfs_fileno_mutex);
   74 }
   75 
   76 /*
   77  * Initialize fileno bitmap
   78  */
   79 void
   80 pfs_fileno_init(struct pfs_info *pi)
   81 {
   82         struct pfs_bitmap *pb;
   83 
   84         MALLOC(pb, struct pfs_bitmap *, sizeof *pb,
   85             M_PFSFILENO, M_WAITOK|M_ZERO);
   86 
   87         mtx_lock(&pi->pi_mutex);
   88 
   89         pb->pb_bitmap[0] = 07;
   90         pb->pb_used = 3;
   91         pi->pi_bitmap = pb;
   92         pi->pi_root->pn_fileno = 2;
   93 
   94         mtx_unlock(&pi->pi_mutex);
   95 }
   96 
   97 /*
   98  * Tear down fileno bitmap
   99  */
  100 void
  101 pfs_fileno_uninit(struct pfs_info *pi)
  102 {
  103         struct pfs_bitmap *pb, *npb;
  104         int used;
  105 
  106         mtx_lock(&pi->pi_mutex);
  107 
  108         pb = pi->pi_bitmap;
  109         pi->pi_bitmap = NULL;
  110 
  111         mtx_unlock(&pi->pi_mutex);
  112 
  113         for (used = 0; pb; pb = npb) {
  114                 npb = pb->pb_next;
  115                 used += pb->pb_used;
  116                 FREE(pb, M_PFSFILENO);
  117         }
  118 #if 0
  119         /* we currently don't reclaim filenos */
  120         if (used > 2)
  121                 printf("WARNING: %d file numbers still in use\n", used);
  122 #endif
  123 }
  124 
  125 /*
  126  * Get the next available file number
  127  */
  128 static u_int32_t
  129 pfs_get_fileno(struct pfs_info *pi)
  130 {
  131         struct pfs_bitmap *pb, *ppb;
  132         u_int32_t fileno;
  133         unsigned int *p;
  134         int i;
  135 
  136         mtx_lock(&pi->pi_mutex);
  137 
  138         /* look for the first page with free bits */
  139         for (ppb = NULL, pb = pi->pi_bitmap; pb; ppb = pb, pb = pb->pb_next)
  140                 if (pb->pb_used != PFS_BITMAP_BITS)
  141                         break;
  142 
  143         /* out of pages? */
  144         if (pb == NULL) {
  145                 mtx_unlock(&pi->pi_mutex);
  146                 MALLOC(pb, struct pfs_bitmap *, sizeof *pb,
  147                     M_PFSFILENO, M_WAITOK|M_ZERO);
  148                 mtx_lock(&pi->pi_mutex);
  149                 /* protect against possible race */
  150                 while (ppb->pb_next)
  151                         ppb = ppb->pb_next;
  152                 pb->pb_offset = ppb->pb_offset + PFS_BITMAP_BITS;
  153                 ppb->pb_next = pb;
  154         }
  155 
  156         /* find the first free slot */
  157         for (i = 0; i < PFS_BITMAP_SIZE; ++i)
  158                 if (pb->pb_bitmap[i] != UINT_MAX)
  159                         break;
  160 
  161         /* find the first available bit and flip it */
  162         fileno = pb->pb_offset + i * PFS_SLOT_BITS;
  163         p = &pb->pb_bitmap[i];
  164         for (i = 0; i < PFS_SLOT_BITS; ++i, ++fileno)
  165                 if ((*p & (unsigned int)(1 << i)) == 0)
  166                         break;
  167         KASSERT(i < PFS_SLOT_BITS,
  168             ("slot has free bits, yet doesn't"));
  169         *p |= (unsigned int)(1 << i);
  170         ++pb->pb_used;
  171 
  172         mtx_unlock(&pi->pi_mutex);
  173 
  174         return fileno;
  175 }
  176 
  177 /*
  178  * Free a file number
  179  */
  180 static void
  181 pfs_free_fileno(struct pfs_info *pi, u_int32_t fileno)
  182 {
  183         struct pfs_bitmap *pb;
  184         unsigned int *p;
  185         int i;
  186 
  187         mtx_lock(&pi->pi_mutex);
  188 
  189         /* find the right page */
  190         for (pb = pi->pi_bitmap;
  191              pb && fileno >= PFS_BITMAP_BITS;
  192              pb = pb->pb_next, fileno -= PFS_BITMAP_BITS)
  193                 /* nothing */ ;
  194         KASSERT(pb,
  195             ("fileno isn't in any bitmap"));
  196 
  197         /* find the right bit in the right slot and flip it */
  198         p = &pb->pb_bitmap[fileno / PFS_SLOT_BITS];
  199         i = fileno % PFS_SLOT_BITS;
  200         KASSERT(*p & (unsigned int)(1 << i),
  201             ("fileno is already free"));
  202         *p &= ~((unsigned int)(1 << i));
  203         --pb->pb_used;
  204 
  205         mtx_unlock(&pi->pi_mutex);
  206         printf("pfs_free_fileno(): reclaimed %d\n", fileno);
  207 }
  208 
  209 /*
  210  * Allocate a file number
  211  */
  212 void
  213 pfs_fileno_alloc(struct pfs_info *pi, struct pfs_node *pn)
  214 {
  215         /* make sure our parent has a file number */
  216         if (pn->pn_parent && !pn->pn_parent->pn_fileno)
  217                 pfs_fileno_alloc(pi, pn->pn_parent);
  218 
  219         switch (pn->pn_type) {
  220         case pfstype_root:
  221         case pfstype_dir:
  222         case pfstype_file:
  223         case pfstype_symlink:
  224         case pfstype_procdir:
  225                 pn->pn_fileno = pfs_get_fileno(pi);
  226                 break;
  227         case pfstype_this:
  228                 KASSERT(pn->pn_parent != NULL,
  229                     ("pfstype_this node has no parent"));
  230                 pn->pn_fileno = pn->pn_parent->pn_fileno;
  231                 break;
  232         case pfstype_parent:
  233                 KASSERT(pn->pn_parent != NULL,
  234                     ("pfstype_parent node has no parent"));
  235                 if (pn->pn_parent == pi->pi_root) {
  236                         pn->pn_fileno = pn->pn_parent->pn_fileno;
  237                         break;
  238                 }
  239                 KASSERT(pn->pn_parent->pn_parent != NULL,
  240                     ("pfstype_parent node has no grandparent"));
  241                 pn->pn_fileno = pn->pn_parent->pn_parent->pn_fileno;
  242                 break;
  243         case pfstype_none:
  244                 KASSERT(0,
  245                     ("pfs_fileno_alloc() called for pfstype_none node"));
  246                 break;
  247         }
  248 
  249 #if 0
  250         printf("pfs_fileno_alloc(): %s: ", pi->pi_name);
  251         if (pn->pn_parent) {
  252                 if (pn->pn_parent->pn_parent) {
  253                         printf("%s/", pn->pn_parent->pn_parent->pn_name);
  254                 }
  255                 printf("%s/", pn->pn_parent->pn_name);
  256         }
  257         printf("%s -> %d\n", pn->pn_name, pn->pn_fileno);
  258 #endif
  259 }
  260 
  261 /*
  262  * Release a file number
  263  */
  264 void
  265 pfs_fileno_free(struct pfs_info *pi, struct pfs_node *pn)
  266 {
  267         switch (pn->pn_type) {
  268         case pfstype_root:
  269         case pfstype_dir:
  270         case pfstype_file:
  271         case pfstype_symlink:
  272         case pfstype_procdir:
  273                 pfs_free_fileno(pi, pn->pn_fileno);
  274                 break;
  275         case pfstype_this:
  276         case pfstype_parent:
  277                 /* ignore these, as they don't "own" their file number */
  278                 break;
  279         case pfstype_none:
  280                 KASSERT(0,
  281                     ("pfs_fileno_free() called for pfstype_none node"));
  282                 break;
  283         }
  284 }

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