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| Rev | Author | Line No. | Line |
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| 2876 | jermar | 1 | /* |
| 2 | * Copyright (c) 2008 Jakub Jermar |
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| 3 | * All rights reserved. |
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| 4 | * |
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| 5 | * Redistribution and use in source and binary forms, with or without |
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| 6 | * modification, are permitted provided that the following conditions |
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| 7 | * are met: |
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| 8 | * |
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| 9 | * - Redistributions of source code must retain the above copyright |
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| 10 | * notice, this list of conditions and the following disclaimer. |
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| 11 | * - Redistributions in binary form must reproduce the above copyright |
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| 12 | * notice, this list of conditions and the following disclaimer in the |
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| 13 | * documentation and/or other materials provided with the distribution. |
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| 14 | * - The name of the author may not be used to endorse or promote products |
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| 15 | * derived from this software without specific prior written permission. |
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| 16 | * |
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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| 27 | */ |
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| 28 | |||
| 29 | /** @addtogroup fs |
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| 30 | * @{ |
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| 31 | */ |
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| 32 | |||
| 33 | /** |
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| 34 | * @file fat_idx.c |
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| 35 | * @brief Layer for translating FAT entities to VFS node indices. |
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| 36 | */ |
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| 37 | |||
| 38 | #include "fat.h" |
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| 2881 | jermar | 39 | #include "../../vfs/vfs.h" |
| 2876 | jermar | 40 | #include <errno.h> |
| 41 | #include <string.h> |
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| 42 | #include <libadt/hash_table.h> |
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| 43 | #include <libadt/list.h> |
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| 44 | #include <assert.h> |
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| 45 | #include <futex.h> |
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| 46 | |||
| 2881 | jermar | 47 | /** Each instance of this type describes one interval of freed VFS indices. */ |
| 48 | typedef struct { |
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| 49 | link_t link; |
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| 50 | fs_index_t first; |
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| 51 | fs_index_t last; |
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| 52 | } freed_t; |
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| 53 | |||
| 54 | /** |
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| 55 | * Each instance of this type describes state of all VFS indices that |
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| 56 | * are currently unused. |
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| 57 | */ |
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| 58 | typedef struct { |
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| 59 | link_t link; |
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| 60 | dev_handle_t dev_handle; |
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| 61 | |||
| 62 | /** Next unassigned index. */ |
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| 63 | fs_index_t next; |
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| 64 | /** Number of remaining unassigned indices. */ |
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| 65 | uint64_t remaining; |
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| 66 | |||
| 67 | /** Sorted list of intervals of freed indices. */ |
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| 68 | link_t freed_head; |
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| 69 | } unused_t; |
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| 70 | |||
| 71 | static LIST_INITIALIZE(unused_head); |
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| 72 | |||
| 73 | /** Allocate a VFS index which is not currently in use. */ |
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| 74 | static bool fat_idx_alloc(dev_handle_t dev_handle, fs_index_t *index) |
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| 2876 | jermar | 75 | { |
| 2881 | jermar | 76 | link_t *l; |
| 77 | unused_t *u; |
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| 78 | |||
| 79 | assert(index); |
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| 80 | for (l = unused_head.next; l != &unused_head; l = l->next) { |
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| 81 | u = list_get_instance(l, unused_t, link); |
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| 82 | if (u->dev_handle == dev_handle) |
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| 83 | goto hit; |
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| 84 | } |
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| 85 | |||
| 86 | /* dev_handle not found */ |
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| 87 | return false; |
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| 88 | |||
| 89 | hit: |
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| 90 | if (list_empty(&u->freed_head)) { |
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| 91 | if (u->remaining) { |
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| 92 | /* |
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| 93 | * There are no freed indices, allocate one directly |
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| 94 | * from the counter. |
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| 95 | */ |
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| 96 | *index = u->next++; |
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| 97 | --u->remaining; |
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| 98 | return true; |
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| 99 | } |
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| 100 | } else { |
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| 101 | /* There are some freed indices which we can reuse. */ |
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| 102 | freed_t *f = list_get_instance(u->freed_head.next, freed_t, |
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| 103 | link); |
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| 104 | *index = f->first; |
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| 105 | if (f->first++ == f->last) { |
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| 106 | /* Destroy the interval. */ |
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| 107 | list_remove(&f->link); |
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| 108 | free(f); |
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| 109 | } |
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| 110 | return true; |
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| 111 | } |
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| 112 | /* |
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| 113 | * We ran out of indices, which is extremely unlikely with FAT16, but |
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| 114 | * theoretically still possible (e.g. too many open unlinked nodes or |
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| 115 | * too many zero-sized nodes). |
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| 116 | */ |
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| 117 | return false; |
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| 118 | } |
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| 119 | |||
| 120 | /** If possible, merge two intervals of freed indices. */ |
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| 121 | static void try_merge_intervals(link_t *l, link_t *r, link_t *cur) |
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| 122 | { |
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| 123 | freed_t *fl = list_get_instance(l, freed_t, link); |
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| 124 | freed_t *fr = list_get_instance(r, freed_t, link); |
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| 125 | |||
| 126 | if (fl->last + 1 == fr->first) { |
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| 127 | if (cur == l) { |
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| 128 | fl->last = fr->last; |
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| 129 | list_remove(r); |
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| 130 | free(r); |
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| 131 | } else { |
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| 132 | fr->first = fl->first; |
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| 133 | list_remove(l); |
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| 134 | free(l); |
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| 135 | } |
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| 136 | } |
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| 137 | } |
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| 138 | |||
| 139 | /** Free a VFS index, which is no longer in use. */ |
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| 140 | static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index) |
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| 141 | { |
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| 142 | link_t *l; |
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| 143 | unused_t *u; |
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| 144 | |||
| 145 | for (l = unused_head.next; l != &unused_head; l = l->next) { |
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| 146 | u = list_get_instance(l, unused_t, link); |
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| 147 | if (u->dev_handle == dev_handle) |
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| 148 | goto hit; |
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| 149 | } |
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| 150 | |||
| 151 | /* should not happen */ |
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| 152 | assert(0); |
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| 153 | |||
| 154 | hit: |
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| 155 | if (u->next == index + 1) { |
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| 156 | /* The index can be returned directly to the counter. */ |
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| 157 | u->next--; |
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| 158 | u->remaining++; |
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| 159 | return; |
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| 160 | } else { |
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| 161 | /* |
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| 162 | * The index must be returned either to an existing freed |
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| 163 | * interval or a new interval must be created. |
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| 164 | */ |
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| 165 | link_t *lnk; |
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| 166 | freed_t *n; |
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| 167 | for (lnk = u->freed_head.next; lnk != &u->freed_head; |
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| 168 | lnk = lnk->next) { |
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| 169 | freed_t *f = list_get_instance(lnk, freed_t, link); |
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| 170 | if (f->first == index + 1) { |
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| 171 | f->first--; |
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| 172 | if (lnk->prev != &u->freed_head) |
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| 173 | try_merge_intervals(lnk->prev, lnk, |
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| 174 | lnk); |
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| 175 | return; |
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| 176 | } |
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| 177 | if (f->last == index - 1) { |
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| 178 | f->last++; |
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| 179 | if (lnk->next != &u->freed_head) |
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| 180 | try_merge_intervals(lnk, lnk->next, |
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| 181 | lnk); |
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| 182 | return; |
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| 183 | } |
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| 184 | if (index > f->first) { |
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| 185 | n = malloc(sizeof(freed_t)); |
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| 186 | /* TODO: sleep until allocation succeeds */ |
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| 187 | assert(n); |
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| 188 | link_initialize(&n->link); |
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| 189 | n->first = index; |
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| 190 | n->last = index; |
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| 191 | list_insert_before(&n->link, lnk); |
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| 192 | return; |
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| 193 | } |
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| 194 | |||
| 195 | } |
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| 196 | /* The index will form the last interval. */ |
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| 197 | n = malloc(sizeof(freed_t)); |
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| 198 | /* TODO: sleep until allocation succeeds */ |
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| 199 | assert(n); |
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| 200 | link_initialize(&n->link); |
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| 201 | n->first = index; |
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| 202 | n->last = index; |
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| 203 | list_append(&n->link, &u->freed_head); |
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| 204 | } |
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| 205 | } |
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| 206 | |||
| 207 | fat_idx_t *fat_idx_map(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi) |
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| 208 | { |
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| 2876 | jermar | 209 | return NULL; /* TODO */ |
| 210 | } |