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2876 jermar 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"
2881 jermar 39
#include "../../vfs/vfs.h"
2876 jermar 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
 
2881 jermar 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
 
3011 svoboda 71
/** Futex protecting the list of unused structures. */
72
static futex_t unused_futex = FUTEX_INITIALIZER;
73
 
74
/** List of unused structures. */
2881 jermar 75
static LIST_INITIALIZE(unused_head);
76
 
3011 svoboda 77
/** Futex protecting the up_hash and ui_hash. */
78
static futex_t used_futex = FUTEX_INITIALIZER;
79
 
2890 jermar 80
/**
81
 * Global hash table of all used fat_idx_t structures.
82
 * The index structures are hashed by the dev_handle, parent node's first
83
 * cluster and index within the parent directory.
84
 */
85
static hash_table_t up_hash;
2889 jermar 86
 
2890 jermar 87
#define UPH_BUCKETS_LOG 12
88
#define UPH_BUCKETS (1 << UPH_BUCKETS_LOG)
2889 jermar 89
 
2890 jermar 90
#define UPH_DH_KEY  0
91
#define UPH_PFC_KEY 1
92
#define UPH_PDI_KEY 2
2889 jermar 93
 
2890 jermar 94
static hash_index_t pos_hash(unsigned long key[])
2889 jermar 95
{
2890 jermar 96
    dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
97
    fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
98
    unsigned pdi = (unsigned)key[UPH_PDI_KEY];
2889 jermar 99
 
100
    hash_index_t h;
101
 
102
    /*
103
     * The least significant half of all bits are the least significant bits
104
     * of the parent node's first cluster.
105
     *
106
     * The least significant half of the most significant half of all bits
107
     * are the least significant bits of the node's dentry index within the
108
     * parent directory node.
109
     *
110
     * The most significant half of the most significant half of all bits
111
     * are the least significant bits of the device handle.
112
     */
2890 jermar 113
    h = pfc & ((1 << (UPH_BUCKETS_LOG / 2)) - 1);
114
    h |= (pdi & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
115
        (UPH_BUCKETS_LOG / 2);
116
    h |= (dev_handle & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
117
        (3 * (UPH_BUCKETS_LOG / 4));
2889 jermar 118
 
119
    return h;
120
}
121
 
2890 jermar 122
static int pos_compare(unsigned long key[], hash_count_t keys, link_t *item)
2889 jermar 123
{
2890 jermar 124
    dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
125
    fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
126
    unsigned pdi = (unsigned)key[UPH_PDI_KEY];
127
    fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uph_link);
2889 jermar 128
 
129
    return (dev_handle == fidx->dev_handle) && (pfc == fidx->pfc) &&
130
        (pdi == fidx->pdi);
131
}
132
 
2890 jermar 133
static void pos_remove_callback(link_t *item)
134
{
135
    /* nothing to do */
136
}
137
 
138
static hash_table_operations_t uph_ops = {
139
    .hash = pos_hash,
140
    .compare = pos_compare,
141
    .remove_callback = pos_remove_callback,
142
};
143
 
144
/**
145
 * Global hash table of all used fat_idx_t structures.
146
 * The index structures are hashed by the dev_handle and index.
147
 */
148
static hash_table_t ui_hash;
149
 
150
#define UIH_BUCKETS_LOG 12
151
#define UIH_BUCKETS (1 << UIH_BUCKETS_LOG)
152
 
153
#define UIH_DH_KEY  0
154
#define UIH_INDEX_KEY   1
155
 
156
static hash_index_t idx_hash(unsigned long key[])
157
{
158
    dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
159
    fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
160
 
161
    hash_index_t h;
162
 
163
    h = dev_handle & ((1 << (UIH_BUCKETS_LOG / 2)) - 1);
164
    h |= (index & ((1 << (UIH_BUCKETS_LOG / 2)) - 1)) <<
165
        (UIH_BUCKETS_LOG / 2);
166
 
167
    return h;
168
}
169
 
170
static int idx_compare(unsigned long key[], hash_count_t keys, link_t *item)
171
{
172
    dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
173
    fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
174
    fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uih_link);
175
 
176
    return (dev_handle == fidx->dev_handle) && (index == fidx->index);
177
}
178
 
2889 jermar 179
static void idx_remove_callback(link_t *item)
180
{
181
    /* nothing to do */
182
}
183
 
2890 jermar 184
static hash_table_operations_t uih_ops = {
2889 jermar 185
    .hash = idx_hash,
186
    .compare = idx_compare,
187
    .remove_callback = idx_remove_callback,
188
};
189
 
2881 jermar 190
/** Allocate a VFS index which is not currently in use. */
191
static bool fat_idx_alloc(dev_handle_t dev_handle, fs_index_t *index)
2876 jermar 192
{
2881 jermar 193
    link_t *l;
194
    unused_t *u;
195
 
196
    assert(index);
3011 svoboda 197
    futex_down(&unused_futex);
2881 jermar 198
    for (l = unused_head.next; l != &unused_head; l = l->next) {
199
        u = list_get_instance(l, unused_t, link);
200
        if (u->dev_handle == dev_handle)
201
            goto hit;
202
    }
3011 svoboda 203
    futex_up(&unused_futex);
204
 
2881 jermar 205
    /* dev_handle not found */
206
    return false;  
207
 
208
hit:
209
    if (list_empty(&u->freed_head)) {
210
        if (u->remaining) {
211
            /*
212
             * There are no freed indices, allocate one directly
213
             * from the counter.
214
             */
215
            *index = u->next++;
216
            --u->remaining;
3011 svoboda 217
            futex_up(&unused_futex);
2881 jermar 218
            return true;
219
        }
220
    } else {
221
        /* There are some freed indices which we can reuse. */
222
        freed_t *f = list_get_instance(u->freed_head.next, freed_t,
223
            link);
224
        *index = f->first;
225
        if (f->first++ == f->last) {
226
            /* Destroy the interval. */
227
            list_remove(&f->link);
228
            free(f);
229
        }
3011 svoboda 230
        futex_up(&unused_futex);
2881 jermar 231
        return true;
232
    }
233
    /*
234
     * We ran out of indices, which is extremely unlikely with FAT16, but
235
     * theoretically still possible (e.g. too many open unlinked nodes or
236
     * too many zero-sized nodes).
237
     */
3011 svoboda 238
    futex_up(&unused_futex);
2881 jermar 239
    return false;
240
}
241
 
2884 jermar 242
/** If possible, coalesce two intervals of freed indices. */
243
static void try_coalesce_intervals(link_t *l, link_t *r, link_t *cur)
2881 jermar 244
{
245
    freed_t *fl = list_get_instance(l, freed_t, link);
246
    freed_t *fr = list_get_instance(r, freed_t, link);
247
 
248
    if (fl->last + 1 == fr->first) {
249
        if (cur == l) {
250
            fl->last = fr->last;
251
            list_remove(r);
252
            free(r);
253
        } else {
254
            fr->first = fl->first;
255
            list_remove(l);
256
            free(l);
257
        }
258
    }
259
}
260
 
261
/** Free a VFS index, which is no longer in use. */
262
static void fat_idx_free(dev_handle_t dev_handle, fs_index_t index)
263
{
264
    link_t *l;
265
    unused_t *u;
266
 
3011 svoboda 267
    futex_down(&unused_futex);
2881 jermar 268
    for (l = unused_head.next; l != &unused_head; l = l->next) {
269
        u = list_get_instance(l, unused_t, link);
270
        if (u->dev_handle == dev_handle)
271
            goto hit;
272
    }
3011 svoboda 273
    futex_up(&unused_futex);
2881 jermar 274
 
275
    /* should not happen */
276
    assert(0);
277
 
278
hit:
279
    if (u->next == index + 1) {
280
        /* The index can be returned directly to the counter. */
281
        u->next--;
282
        u->remaining++;
283
    } else {
284
        /*
285
         * The index must be returned either to an existing freed
286
         * interval or a new interval must be created.
287
         */
288
        link_t *lnk;
289
        freed_t *n;
290
        for (lnk = u->freed_head.next; lnk != &u->freed_head;
291
            lnk = lnk->next) {
292
            freed_t *f = list_get_instance(lnk, freed_t, link);
293
            if (f->first == index + 1) {
294
                f->first--;
295
                if (lnk->prev != &u->freed_head)
2884 jermar 296
                    try_coalesce_intervals(lnk->prev, lnk,
2881 jermar 297
                        lnk);
3011 svoboda 298
                futex_up(&unused_futex);
2881 jermar 299
                return;
300
            }
301
            if (f->last == index - 1) {
302
                f->last++;
303
                if (lnk->next != &u->freed_head)
2884 jermar 304
                    try_coalesce_intervals(lnk, lnk->next,
2881 jermar 305
                        lnk);
3011 svoboda 306
                futex_up(&unused_futex);
2881 jermar 307
                return;
308
            }
309
            if (index > f->first) {
310
                n = malloc(sizeof(freed_t));
311
                /* TODO: sleep until allocation succeeds */
312
                assert(n);
313
                link_initialize(&n->link);
314
                n->first = index;
315
                n->last = index;
316
                list_insert_before(&n->link, lnk);
3011 svoboda 317
                futex_up(&unused_futex);
2881 jermar 318
                return;
319
            }
320
 
321
        }
322
        /* The index will form the last interval. */
323
        n = malloc(sizeof(freed_t));
324
        /* TODO: sleep until allocation succeeds */
325
        assert(n);
326
        link_initialize(&n->link);
327
        n->first = index;
328
        n->last = index;
329
        list_append(&n->link, &u->freed_head);
330
    }
3011 svoboda 331
    futex_up(&unused_futex);
2881 jermar 332
}
333
 
2890 jermar 334
fat_idx_t *
335
fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
2881 jermar 336
{
2889 jermar 337
    fat_idx_t *fidx;
338
    link_t *l;
2890 jermar 339
    unsigned long pkey[] = {
340
        [UPH_DH_KEY] = dev_handle,
341
        [UPH_PFC_KEY] = pfc,
342
        [UPH_PDI_KEY] = pdi,
2889 jermar 343
    };
344
 
3011 svoboda 345
    futex_down(&used_futex);
2890 jermar 346
    l = hash_table_find(&up_hash, pkey);
2889 jermar 347
    if (l) {
2890 jermar 348
        fidx = hash_table_get_instance(l, fat_idx_t, uph_link);
2889 jermar 349
    } else {
350
        fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));
351
        if (!fidx) {
3011 svoboda 352
            futex_up(&used_futex);
2889 jermar 353
            return NULL;
354
        }
355
        if (!fat_idx_alloc(dev_handle, &fidx->index)) {
356
            free(fidx);
3011 svoboda 357
            futex_up(&used_futex);
2889 jermar 358
            return NULL;
359
        }
2890 jermar 360
 
361
        unsigned long ikey[] = {
362
            [UIH_DH_KEY] = dev_handle,
363
            [UIH_INDEX_KEY] = fidx->index,
364
        };
365
 
366
        link_initialize(&fidx->uph_link);
367
        link_initialize(&fidx->uih_link);
3011 svoboda 368
        futex_initialize(&fidx->lock, 1);
2889 jermar 369
        fidx->dev_handle = dev_handle;
370
        fidx->pfc = pfc;
371
        fidx->pdi = pdi;
372
        fidx->nodep = NULL;
2890 jermar 373
 
374
        hash_table_insert(&up_hash, pkey, &fidx->uph_link);
375
        hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
2889 jermar 376
    }
3011 svoboda 377
    futex_down(&fidx->lock);
378
    futex_up(&used_futex);
2889 jermar 379
 
380
    return fidx;
2876 jermar 381
}
2889 jermar 382
 
2890 jermar 383
fat_idx_t *
384
fat_idx_get_by_index(dev_handle_t dev_handle, fs_index_t index)
385
{
386
    fat_idx_t *fidx = NULL;
387
    link_t *l;
388
    unsigned long ikey[] = {
389
        [UIH_DH_KEY] = dev_handle,
390
        [UIH_INDEX_KEY] = index,
391
    };
392
 
3011 svoboda 393
    futex_down(&used_futex);
2890 jermar 394
    l = hash_table_find(&ui_hash, ikey);
395
    if (l) {
396
        fidx = hash_table_get_instance(l, fat_idx_t, uih_link);
3011 svoboda 397
        futex_down(&fidx->lock);
2890 jermar 398
    }
3011 svoboda 399
    futex_up(&used_futex);
2890 jermar 400
 
401
    return fidx;
402
}
403