Subversion Repositories HelenOS

Rev

Rev 2884 | Rev 2890 | Go to most recent revision | Blame | Compare with Previous | Last modification | View Log | Download | RSS feed

  1. /*
  2.  * Copyright (c) 2008 Jakub Jermar
  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.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - 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.  * - 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. /** @addtogroup fs
  30.  * @{
  31.  */
  32.  
  33. /**
  34.  * @file    fat_idx.c
  35.  * @brief   Layer for translating FAT entities to VFS node indices.
  36.  */
  37.  
  38. #include "fat.h"
  39. #include "../../vfs/vfs.h"
  40. #include <errno.h>
  41. #include <string.h>
  42. #include <libadt/hash_table.h>
  43. #include <libadt/list.h>
  44. #include <assert.h>
  45. #include <futex.h>
  46.  
  47. /** Each instance of this type describes one interval of freed VFS indices. */
  48. typedef struct {
  49.     link_t      link;
  50.     fs_index_t  first;
  51.     fs_index_t  last;
  52. } freed_t;
  53.  
  54. /**
  55.  * Each instance of this type describes state of all VFS indices that
  56.  * are currently unused.
  57.  */
  58. typedef struct {
  59.     link_t      link;
  60.     dev_handle_t    dev_handle;
  61.  
  62.     /** Next unassigned index. */
  63.     fs_index_t  next;
  64.     /** Number of remaining unassigned indices. */
  65.     uint64_t    remaining;
  66.  
  67.     /** Sorted list of intervals of freed indices. */
  68.     link_t      freed_head;
  69. } unused_t;
  70.  
  71. static LIST_INITIALIZE(unused_head);
  72.  
  73. /** Global hash table of all used fat_idx_t structures. */
  74. static hash_table_t used_hash;
  75.  
  76. #define USED_HASH_BUCKETS_LOG   12
  77. #define USED_HASH_BUCKETS   (1 << USED_HASH_BUCKETS_LOG)
  78.  
  79. #define USED_HASH_DH_KEY    0
  80. #define USED_HASH_PFC_KEY   1
  81. #define USED_HASH_PDI_KEY   2
  82.  
  83. static hash_index_t idx_hash(unsigned long key[])
  84. {
  85.     dev_handle_t dev_handle = (dev_handle_t)key[USED_HASH_DH_KEY];
  86.     fat_cluster_t pfc = (fat_cluster_t)key[USED_HASH_PFC_KEY];
  87.     unsigned pdi = (unsigned)key[USED_HASH_PDI_KEY];
  88.  
  89.     hash_index_t h;
  90.  
  91.     /*
  92.      * The least significant half of all bits are the least significant bits
  93.      * of the parent node's first cluster.
  94.      *
  95.      * The least significant half of the most significant half of all bits
  96.      * are the least significant bits of the node's dentry index within the
  97.      * parent directory node.
  98.      *
  99.      * The most significant half of the most significant half of all bits
  100.      * are the least significant bits of the device handle.
  101.      */
  102.     h = pfc & ((USED_HASH_BUCKETS_LOG / 2) - 1);
  103.     h |= (pdi & ((USED_HASH_BUCKETS_LOG / 4) - 1)) <<
  104.         (USED_HASH_BUCKETS_LOG / 2);
  105.     h |= (dev_handle & ((USED_HASH_BUCKETS_LOG / 4) - 1)) <<
  106.         (3 * (USED_HASH_BUCKETS_LOG / 4));
  107.  
  108.     return h;
  109. }
  110.  
  111. static int idx_compare(unsigned long key[], hash_count_t keys, link_t *item)
  112. {
  113.     dev_handle_t dev_handle = (dev_handle_t)key[USED_HASH_DH_KEY];
  114.     fat_cluster_t pfc = (fat_cluster_t)key[USED_HASH_PFC_KEY];
  115.     unsigned pdi = (unsigned)key[USED_HASH_PDI_KEY];
  116.     fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uh_link);
  117.  
  118.     return (dev_handle == fidx->dev_handle) && (pfc == fidx->pfc) &&
  119.         (pdi == fidx->pdi);
  120. }
  121.  
  122. static void idx_remove_callback(link_t *item)
  123. {
  124.     /* nothing to do */
  125. }
  126.  
  127. static hash_table_operations_t used_idx_ops = {
  128.     .hash = idx_hash,
  129.     .compare = idx_compare,
  130.     .remove_callback = idx_remove_callback,
  131. };
  132.  
  133. /** Allocate a VFS index which is not currently in use. */
  134. static bool fat_idx_alloc(dev_handle_t dev_handle, fs_index_t *index)
  135. {
  136.     link_t *l;
  137.     unused_t *u;
  138.    
  139.     assert(index);
  140.     for (l = unused_head.next; l != &unused_head; l = l->next) {
  141.         u = list_get_instance(l, unused_t, link);
  142.         if (u->dev_handle == dev_handle)
  143.             goto hit;
  144.     }
  145.  
  146.     /* dev_handle not found */
  147.     return false;  
  148.  
  149. hit:
  150.     if (list_empty(&u->freed_head)) {
  151.         if (u->remaining) {
  152.             /*
  153.              * There are no freed indices, allocate one directly
  154.              * from the counter.
  155.              */
  156.             *index = u->next++;
  157.             --u->remaining;
  158.             return true;
  159.         }
  160.     } else {
  161.         /* There are some freed indices which we can reuse. */
  162.         freed_t *f = list_get_instance(u->freed_head.next, freed_t,
  163.             link);
  164.         *index = f->first;
  165.         if (f->first++ == f->last) {
  166.             /* Destroy the interval. */
  167.             list_remove(&f->link);
  168.             free(f);
  169.         }
  170.         return true;
  171.     }
  172.     /*
  173.      * We ran out of indices, which is extremely unlikely with FAT16, but
  174.      * theoretically still possible (e.g. too many open unlinked nodes or
  175.      * too many zero-sized nodes).
  176.      */
  177.     return false;
  178. }
  179.  
  180. /** If possible, coalesce two intervals of freed indices. */
  181. static void try_coalesce_intervals(link_t *l, link_t *r, link_t *cur)
  182. {
  183.     freed_t *fl = list_get_instance(l, freed_t, link);
  184.     freed_t *fr = list_get_instance(r, freed_t, link);
  185.  
  186.     if (fl->last + 1 == fr->first) {
  187.         if (cur == l) {
  188.             fl->last = fr->last;
  189.             list_remove(r);
  190.             free(r);
  191.         } else {
  192.             fr->first = fl->first;
  193.             list_remove(l);
  194.             free(l);
  195.         }
  196.     }
  197. }
  198.  
  199. /** Free a VFS index, which is no longer in use. */
  200. static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)
  201. {
  202.     link_t *l;
  203.     unused_t *u;
  204.  
  205.     for (l = unused_head.next; l != &unused_head; l = l->next) {
  206.         u = list_get_instance(l, unused_t, link);
  207.         if (u->dev_handle == dev_handle)
  208.             goto hit;
  209.     }
  210.  
  211.     /* should not happen */
  212.     assert(0);
  213.  
  214. hit:
  215.     if (u->next == index + 1) {
  216.         /* The index can be returned directly to the counter. */
  217.         u->next--;
  218.         u->remaining++;
  219.         return;
  220.     } else {
  221.         /*
  222.          * The index must be returned either to an existing freed
  223.          * interval or a new interval must be created.
  224.          */
  225.         link_t *lnk;
  226.         freed_t *n;
  227.         for (lnk = u->freed_head.next; lnk != &u->freed_head;
  228.             lnk = lnk->next) {
  229.             freed_t *f = list_get_instance(lnk, freed_t, link);
  230.             if (f->first == index + 1) {
  231.                 f->first--;
  232.                 if (lnk->prev != &u->freed_head)
  233.                     try_coalesce_intervals(lnk->prev, lnk,
  234.                         lnk);
  235.                 return;
  236.             }
  237.             if (f->last == index - 1) {
  238.                 f->last++;
  239.                 if (lnk->next != &u->freed_head)
  240.                     try_coalesce_intervals(lnk, lnk->next,
  241.                         lnk);
  242.                 return;
  243.             }
  244.             if (index > f->first) {
  245.                 n = malloc(sizeof(freed_t));
  246.                 /* TODO: sleep until allocation succeeds */
  247.                 assert(n);
  248.                 link_initialize(&n->link);
  249.                 n->first = index;
  250.                 n->last = index;
  251.                 list_insert_before(&n->link, lnk);
  252.                 return;
  253.             }
  254.  
  255.         }
  256.         /* The index will form the last interval. */
  257.         n = malloc(sizeof(freed_t));
  258.         /* TODO: sleep until allocation succeeds */
  259.         assert(n);
  260.         link_initialize(&n->link);
  261.         n->first = index;
  262.         n->last = index;
  263.         list_append(&n->link, &u->freed_head);
  264.     }
  265. }
  266.  
  267. fat_idx_t *fat_idx_map(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
  268. {
  269.     fat_idx_t *fidx;
  270.     link_t *l;
  271.     unsigned long key[] = {
  272.         [USED_HASH_DH_KEY] = dev_handle,
  273.         [USED_HASH_PFC_KEY] = pfc,
  274.         [USED_HASH_PDI_KEY] = pdi,
  275.     };
  276.  
  277.     l = hash_table_find(&used_hash, key);
  278.     if (l) {
  279.         fidx = hash_table_get_instance(l, fat_idx_t, uh_link);
  280.     } else {
  281.         fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));
  282.         if (!fidx) {
  283.             return NULL;
  284.         }
  285.         if (!fat_idx_alloc(dev_handle, &fidx->index)) {
  286.             free(fidx);
  287.             return NULL;
  288.         }
  289.         link_initialize(&fidx->uh_link);
  290.         fidx->dev_handle = dev_handle;
  291.         fidx->pfc = pfc;
  292.         fidx->pdi = pdi;
  293.         fidx->nodep = NULL;
  294.         hash_table_insert(&used_hash, key, &fidx->uh_link);
  295.     }
  296.  
  297.     return fidx;
  298. }
  299.  
  300.