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  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. /** Futex protecting the list of unused structures. */
  72. static futex_t unused_futex = FUTEX_INITIALIZER;
  73.  
  74. /** List of unused structures. */
  75. static LIST_INITIALIZE(unused_head);
  76.  
  77. /**
  78.  * Global hash table of all used fat_idx_t structures.
  79.  * The index structures are hashed by the dev_handle, parent node's first
  80.  * cluster and index within the parent directory.
  81.  */
  82. static hash_table_t up_hash;
  83.  
  84. #define UPH_BUCKETS_LOG 12
  85. #define UPH_BUCKETS (1 << UPH_BUCKETS_LOG)
  86.  
  87. #define UPH_DH_KEY  0
  88. #define UPH_PFC_KEY 1
  89. #define UPH_PDI_KEY 2
  90.  
  91. static hash_index_t pos_hash(unsigned long key[])
  92. {
  93.     dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
  94.     fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
  95.     unsigned pdi = (unsigned)key[UPH_PDI_KEY];
  96.  
  97.     hash_index_t h;
  98.  
  99.     /*
  100.      * The least significant half of all bits are the least significant bits
  101.      * of the parent node's first cluster.
  102.      *
  103.      * The least significant half of the most significant half of all bits
  104.      * are the least significant bits of the node's dentry index within the
  105.      * parent directory node.
  106.      *
  107.      * The most significant half of the most significant half of all bits
  108.      * are the least significant bits of the device handle.
  109.      */
  110.     h = pfc & ((1 << (UPH_BUCKETS_LOG / 2)) - 1);
  111.     h |= (pdi & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
  112.         (UPH_BUCKETS_LOG / 2);
  113.     h |= (dev_handle & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
  114.         (3 * (UPH_BUCKETS_LOG / 4));
  115.  
  116.     return h;
  117. }
  118.  
  119. static int pos_compare(unsigned long key[], hash_count_t keys, link_t *item)
  120. {
  121.     dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
  122.     fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
  123.     unsigned pdi = (unsigned)key[UPH_PDI_KEY];
  124.     fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uph_link);
  125.  
  126.     return (dev_handle == fidx->dev_handle) && (pfc == fidx->pfc) &&
  127.         (pdi == fidx->pdi);
  128. }
  129.  
  130. static void pos_remove_callback(link_t *item)
  131. {
  132.     /* nothing to do */
  133. }
  134.  
  135. static hash_table_operations_t uph_ops = {
  136.     .hash = pos_hash,
  137.     .compare = pos_compare,
  138.     .remove_callback = pos_remove_callback,
  139. };
  140.  
  141. /**
  142.  * Global hash table of all used fat_idx_t structures.
  143.  * The index structures are hashed by the dev_handle and index.
  144.  */
  145. static hash_table_t ui_hash;
  146.  
  147. #define UIH_BUCKETS_LOG 12
  148. #define UIH_BUCKETS (1 << UIH_BUCKETS_LOG)
  149.  
  150. #define UIH_DH_KEY  0
  151. #define UIH_INDEX_KEY   1
  152.  
  153. static hash_index_t idx_hash(unsigned long key[])
  154. {
  155.     dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
  156.     fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
  157.  
  158.     hash_index_t h;
  159.  
  160.     h = dev_handle & ((1 << (UIH_BUCKETS_LOG / 2)) - 1);
  161.     h |= (index & ((1 << (UIH_BUCKETS_LOG / 2)) - 1)) <<
  162.         (UIH_BUCKETS_LOG / 2);
  163.  
  164.     return h;
  165. }
  166.  
  167. static int idx_compare(unsigned long key[], hash_count_t keys, link_t *item)
  168. {
  169.     dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
  170.     fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
  171.     fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uih_link);
  172.  
  173.     return (dev_handle == fidx->dev_handle) && (index == fidx->index);
  174. }
  175.  
  176. static void idx_remove_callback(link_t *item)
  177. {
  178.     /* nothing to do */
  179. }
  180.  
  181. static hash_table_operations_t uih_ops = {
  182.     .hash = idx_hash,
  183.     .compare = idx_compare,
  184.     .remove_callback = idx_remove_callback,
  185. };
  186.  
  187. /** Allocate a VFS index which is not currently in use. */
  188. static bool fat_idx_alloc(dev_handle_t dev_handle, fs_index_t *index)
  189. {
  190.     link_t *l;
  191.     unused_t *u;
  192.    
  193.     assert(index);
  194.     futex_down(&unused_futex);
  195.     for (l = unused_head.next; l != &unused_head; l = l->next) {
  196.         u = list_get_instance(l, unused_t, link);
  197.         if (u->dev_handle == dev_handle)
  198.             goto hit;
  199.     }
  200.     futex_up(&unused_futex);
  201.    
  202.     /* dev_handle not found */
  203.     return false;  
  204.  
  205. hit:
  206.     if (list_empty(&u->freed_head)) {
  207.         if (u->remaining) {
  208.             /*
  209.              * There are no freed indices, allocate one directly
  210.              * from the counter.
  211.              */
  212.             *index = u->next++;
  213.             --u->remaining;
  214.             futex_up(&unused_futex);
  215.             return true;
  216.         }
  217.     } else {
  218.         /* There are some freed indices which we can reuse. */
  219.         freed_t *f = list_get_instance(u->freed_head.next, freed_t,
  220.             link);
  221.         *index = f->first;
  222.         if (f->first++ == f->last) {
  223.             /* Destroy the interval. */
  224.             list_remove(&f->link);
  225.             free(f);
  226.         }
  227.         futex_up(&unused_futex);
  228.         return true;
  229.     }
  230.     /*
  231.      * We ran out of indices, which is extremely unlikely with FAT16, but
  232.      * theoretically still possible (e.g. too many open unlinked nodes or
  233.      * too many zero-sized nodes).
  234.      */
  235.     futex_up(&unused_futex);
  236.     return false;
  237. }
  238.  
  239. /** If possible, coalesce two intervals of freed indices. */
  240. static void try_coalesce_intervals(link_t *l, link_t *r, link_t *cur)
  241. {
  242.     freed_t *fl = list_get_instance(l, freed_t, link);
  243.     freed_t *fr = list_get_instance(r, freed_t, link);
  244.  
  245.     if (fl->last + 1 == fr->first) {
  246.         if (cur == l) {
  247.             fl->last = fr->last;
  248.             list_remove(r);
  249.             free(r);
  250.         } else {
  251.             fr->first = fl->first;
  252.             list_remove(l);
  253.             free(l);
  254.         }
  255.     }
  256. }
  257.  
  258. /** Free a VFS index, which is no longer in use. */
  259. static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)
  260. {
  261.     link_t *l;
  262.     unused_t *u;
  263.  
  264.     futex_down(&unused_futex);
  265.     for (l = unused_head.next; l != &unused_head; l = l->next) {
  266.         u = list_get_instance(l, unused_t, link);
  267.         if (u->dev_handle == dev_handle)
  268.             goto hit;
  269.     }
  270.     futex_up(&unused_futex);
  271.  
  272.     /* should not happen */
  273.     assert(0);
  274.  
  275. hit:
  276.     if (u->next == index + 1) {
  277.         /* The index can be returned directly to the counter. */
  278.         u->next--;
  279.         u->remaining++;
  280.     } else {
  281.         /*
  282.          * The index must be returned either to an existing freed
  283.          * interval or a new interval must be created.
  284.          */
  285.         link_t *lnk;
  286.         freed_t *n;
  287.         for (lnk = u->freed_head.next; lnk != &u->freed_head;
  288.             lnk = lnk->next) {
  289.             freed_t *f = list_get_instance(lnk, freed_t, link);
  290.             if (f->first == index + 1) {
  291.                 f->first--;
  292.                 if (lnk->prev != &u->freed_head)
  293.                     try_coalesce_intervals(lnk->prev, lnk,
  294.                         lnk);
  295.                 futex_up(&unused_futex);
  296.                 return;
  297.             }
  298.             if (f->last == index - 1) {
  299.                 f->last++;
  300.                 if (lnk->next != &u->freed_head)
  301.                     try_coalesce_intervals(lnk, lnk->next,
  302.                         lnk);
  303.                 futex_up(&unused_futex);
  304.                 return;
  305.             }
  306.             if (index > f->first) {
  307.                 n = malloc(sizeof(freed_t));
  308.                 /* TODO: sleep until allocation succeeds */
  309.                 assert(n);
  310.                 link_initialize(&n->link);
  311.                 n->first = index;
  312.                 n->last = index;
  313.                 list_insert_before(&n->link, lnk);
  314.                 futex_up(&unused_futex);
  315.                 return;
  316.             }
  317.  
  318.         }
  319.         /* The index will form the last interval. */
  320.         n = malloc(sizeof(freed_t));
  321.         /* TODO: sleep until allocation succeeds */
  322.         assert(n);
  323.         link_initialize(&n->link);
  324.         n->first = index;
  325.         n->last = index;
  326.         list_append(&n->link, &u->freed_head);
  327.     }
  328.     futex_up(&unused_futex);
  329. }
  330.  
  331. fat_idx_t *
  332. fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
  333. {
  334.     fat_idx_t *fidx;
  335.     link_t *l;
  336.     unsigned long pkey[] = {
  337.         [UPH_DH_KEY] = dev_handle,
  338.         [UPH_PFC_KEY] = pfc,
  339.         [UPH_PDI_KEY] = pdi,
  340.     };
  341.  
  342.     l = hash_table_find(&up_hash, pkey);
  343.     if (l) {
  344.         fidx = hash_table_get_instance(l, fat_idx_t, uph_link);
  345.     } else {
  346.         fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));
  347.         if (!fidx) {
  348.             return NULL;
  349.         }
  350.         if (!fat_idx_alloc(dev_handle, &fidx->index)) {
  351.             free(fidx);
  352.             return NULL;
  353.         }
  354.        
  355.         unsigned long ikey[] = {
  356.             [UIH_DH_KEY] = dev_handle,
  357.             [UIH_INDEX_KEY] = fidx->index,
  358.         };
  359.    
  360.         link_initialize(&fidx->uph_link);
  361.         link_initialize(&fidx->uih_link);
  362.         fidx->dev_handle = dev_handle;
  363.         fidx->pfc = pfc;
  364.         fidx->pdi = pdi;
  365.         fidx->nodep = NULL;
  366.  
  367.         hash_table_insert(&up_hash, pkey, &fidx->uph_link);
  368.         hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
  369.     }
  370.  
  371.     return fidx;
  372. }
  373.  
  374. fat_idx_t *
  375. fat_idx_get_by_index(dev_handle_t dev_handle, fs_index_t index)
  376. {
  377.     fat_idx_t *fidx = NULL;
  378.     link_t *l;
  379.     unsigned long ikey[] = {
  380.         [UIH_DH_KEY] = dev_handle,
  381.         [UIH_INDEX_KEY] = index,
  382.     };
  383.  
  384.     l = hash_table_find(&ui_hash, ikey);
  385.     if (l) {
  386.         fidx = hash_table_get_instance(l, fat_idx_t, uih_link);
  387.     }
  388.  
  389.     return fidx;
  390. }
  391.  
  392.