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4419 trochtova 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>
4537 trochtova 42
#include <adt/hash_table.h>
43
#include <adt/list.h>
4419 trochtova 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
static void unused_initialize(unused_t *u, dev_handle_t dev_handle)
78
{
79
    link_initialize(&u->link);
80
    u->dev_handle = dev_handle;
81
    u->next = 0;
82
    u->remaining = ((uint64_t)((fs_index_t)-1)) + 1;
83
    list_initialize(&u->freed_head);
84
}
85
 
86
static unused_t *unused_find(dev_handle_t dev_handle, bool lock)
87
{
88
    unused_t *u;
89
    link_t *l;
90
 
91
    if (lock)
92
        futex_down(&unused_futex);
93
    for (l = unused_head.next; l != &unused_head; l = l->next) {
94
        u = list_get_instance(l, unused_t, link);
95
        if (u->dev_handle == dev_handle)
96
            return u;
97
    }
98
    if (lock)
99
        futex_up(&unused_futex);
100
    return NULL;
101
}
102
 
103
/** Futex protecting the up_hash and ui_hash. */
104
static futex_t used_futex = FUTEX_INITIALIZER;
105
 
106
/**
107
 * Global hash table of all used fat_idx_t structures.
108
 * The index structures are hashed by the dev_handle, parent node's first
109
 * cluster and index within the parent directory.
110
 */
111
static hash_table_t up_hash;
112
 
113
#define UPH_BUCKETS_LOG 12
114
#define UPH_BUCKETS (1 << UPH_BUCKETS_LOG)
115
 
116
#define UPH_DH_KEY  0
117
#define UPH_PFC_KEY 1
118
#define UPH_PDI_KEY 2
119
 
120
static hash_index_t pos_hash(unsigned long key[])
121
{
122
    dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
123
    fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
124
    unsigned pdi = (unsigned)key[UPH_PDI_KEY];
125
 
126
    hash_index_t h;
127
 
128
    /*
129
     * The least significant half of all bits are the least significant bits
130
     * of the parent node's first cluster.
131
     *
132
     * The least significant half of the most significant half of all bits
133
     * are the least significant bits of the node's dentry index within the
134
     * parent directory node.
135
     *
136
     * The most significant half of the most significant half of all bits
137
     * are the least significant bits of the device handle.
138
     */
139
    h = pfc & ((1 << (UPH_BUCKETS_LOG / 2)) - 1);
140
    h |= (pdi & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
141
        (UPH_BUCKETS_LOG / 2);
142
    h |= (dev_handle & ((1 << (UPH_BUCKETS_LOG / 4)) - 1)) <<
143
        (3 * (UPH_BUCKETS_LOG / 4));
144
 
145
    return h;
146
}
147
 
148
static int pos_compare(unsigned long key[], hash_count_t keys, link_t *item)
149
{
150
    dev_handle_t dev_handle = (dev_handle_t)key[UPH_DH_KEY];
151
    fat_cluster_t pfc = (fat_cluster_t)key[UPH_PFC_KEY];
152
    unsigned pdi = (unsigned)key[UPH_PDI_KEY];
153
    fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uph_link);
154
 
155
    return (dev_handle == fidx->dev_handle) && (pfc == fidx->pfc) &&
156
        (pdi == fidx->pdi);
157
}
158
 
159
static void pos_remove_callback(link_t *item)
160
{
161
    /* nothing to do */
162
}
163
 
164
static hash_table_operations_t uph_ops = {
165
    .hash = pos_hash,
166
    .compare = pos_compare,
167
    .remove_callback = pos_remove_callback,
168
};
169
 
170
/**
171
 * Global hash table of all used fat_idx_t structures.
172
 * The index structures are hashed by the dev_handle and index.
173
 */
174
static hash_table_t ui_hash;
175
 
176
#define UIH_BUCKETS_LOG 12
177
#define UIH_BUCKETS (1 << UIH_BUCKETS_LOG)
178
 
179
#define UIH_DH_KEY  0
180
#define UIH_INDEX_KEY   1
181
 
182
static hash_index_t idx_hash(unsigned long key[])
183
{
184
    dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
185
    fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
186
 
187
    hash_index_t h;
188
 
189
    h = dev_handle & ((1 << (UIH_BUCKETS_LOG / 2)) - 1);
190
    h |= (index & ((1 << (UIH_BUCKETS_LOG / 2)) - 1)) <<
191
        (UIH_BUCKETS_LOG / 2);
192
 
193
    return h;
194
}
195
 
196
static int idx_compare(unsigned long key[], hash_count_t keys, link_t *item)
197
{
198
    dev_handle_t dev_handle = (dev_handle_t)key[UIH_DH_KEY];
199
    fs_index_t index = (fs_index_t)key[UIH_INDEX_KEY];
200
    fat_idx_t *fidx = list_get_instance(item, fat_idx_t, uih_link);
201
 
202
    return (dev_handle == fidx->dev_handle) && (index == fidx->index);
203
}
204
 
205
static void idx_remove_callback(link_t *item)
206
{
207
    /* nothing to do */
208
}
209
 
210
static hash_table_operations_t uih_ops = {
211
    .hash = idx_hash,
212
    .compare = idx_compare,
213
    .remove_callback = idx_remove_callback,
214
};
215
 
216
/** Allocate a VFS index which is not currently in use. */
217
static bool fat_index_alloc(dev_handle_t dev_handle, fs_index_t *index)
218
{
219
    unused_t *u;
220
 
221
    assert(index);
222
    u = unused_find(dev_handle, true);
223
    if (!u)
224
        return false;  
225
 
226
    if (list_empty(&u->freed_head)) {
227
        if (u->remaining) {
228
            /*
229
             * There are no freed indices, allocate one directly
230
             * from the counter.
231
             */
232
            *index = u->next++;
233
            --u->remaining;
234
            futex_up(&unused_futex);
235
            return true;
236
        }
237
    } else {
238
        /* There are some freed indices which we can reuse. */
239
        freed_t *f = list_get_instance(u->freed_head.next, freed_t,
240
            link);
241
        *index = f->first;
242
        if (f->first++ == f->last) {
243
            /* Destroy the interval. */
244
            list_remove(&f->link);
245
            free(f);
246
        }
247
        futex_up(&unused_futex);
248
        return true;
249
    }
250
    /*
251
     * We ran out of indices, which is extremely unlikely with FAT16, but
252
     * theoretically still possible (e.g. too many open unlinked nodes or
253
     * too many zero-sized nodes).
254
     */
255
    futex_up(&unused_futex);
256
    return false;
257
}
258
 
259
/** If possible, coalesce two intervals of freed indices. */
260
static void try_coalesce_intervals(link_t *l, link_t *r, link_t *cur)
261
{
262
    freed_t *fl = list_get_instance(l, freed_t, link);
263
    freed_t *fr = list_get_instance(r, freed_t, link);
264
 
265
    if (fl->last + 1 == fr->first) {
266
        if (cur == l) {
267
            fl->last = fr->last;
268
            list_remove(r);
269
            free(r);
270
        } else {
271
            fr->first = fl->first;
272
            list_remove(l);
273
            free(l);
274
        }
275
    }
276
}
277
 
278
/** Free a VFS index, which is no longer in use. */
279
static void fat_index_free(dev_handle_t dev_handle, fs_index_t index)
280
{
281
    unused_t *u;
282
 
283
    u = unused_find(dev_handle, true);
284
    assert(u);
285
 
286
    if (u->next == index + 1) {
287
        /* The index can be returned directly to the counter. */
288
        u->next--;
289
        u->remaining++;
290
    } else {
291
        /*
292
         * The index must be returned either to an existing freed
293
         * interval or a new interval must be created.
294
         */
295
        link_t *lnk;
296
        freed_t *n;
297
        for (lnk = u->freed_head.next; lnk != &u->freed_head;
298
            lnk = lnk->next) {
299
            freed_t *f = list_get_instance(lnk, freed_t, link);
300
            if (f->first == index + 1) {
301
                f->first--;
302
                if (lnk->prev != &u->freed_head)
303
                    try_coalesce_intervals(lnk->prev, lnk,
304
                        lnk);
305
                futex_up(&unused_futex);
306
                return;
307
            }
308
            if (f->last == index - 1) {
309
                f->last++;
310
                if (lnk->next != &u->freed_head)
311
                    try_coalesce_intervals(lnk, lnk->next,
312
                        lnk);
313
                futex_up(&unused_futex);
314
                return;
315
            }
316
            if (index > f->first) {
317
                n = malloc(sizeof(freed_t));
318
                /* TODO: sleep until allocation succeeds */
319
                assert(n);
320
                link_initialize(&n->link);
321
                n->first = index;
322
                n->last = index;
323
                list_insert_before(&n->link, lnk);
324
                futex_up(&unused_futex);
325
                return;
326
            }
327
 
328
        }
329
        /* The index will form the last interval. */
330
        n = malloc(sizeof(freed_t));
331
        /* TODO: sleep until allocation succeeds */
332
        assert(n);
333
        link_initialize(&n->link);
334
        n->first = index;
335
        n->last = index;
336
        list_append(&n->link, &u->freed_head);
337
    }
338
    futex_up(&unused_futex);
339
}
340
 
341
static fat_idx_t *fat_idx_create(dev_handle_t dev_handle)
342
{
343
    fat_idx_t *fidx;
344
 
345
    fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));
346
    if (!fidx)
347
        return NULL;
348
    if (!fat_index_alloc(dev_handle, &fidx->index)) {
349
        free(fidx);
350
        return NULL;
351
    }
352
 
353
    link_initialize(&fidx->uph_link);
354
    link_initialize(&fidx->uih_link);
355
    futex_initialize(&fidx->lock, 1);
356
    fidx->dev_handle = dev_handle;
357
    fidx->pfc = FAT_CLST_RES0;  /* no parent yet */
358
    fidx->pdi = 0;
359
    fidx->nodep = NULL;
360
 
361
    return fidx;
362
}
363
 
364
fat_idx_t *fat_idx_get_new(dev_handle_t dev_handle)
365
{
366
    fat_idx_t *fidx;
367
 
368
    futex_down(&used_futex);
369
    fidx = fat_idx_create(dev_handle);
370
    if (!fidx) {
371
        futex_up(&used_futex);
372
        return NULL;
373
    }
374
 
375
    unsigned long ikey[] = {
376
        [UIH_DH_KEY] = dev_handle,
377
        [UIH_INDEX_KEY] = fidx->index,
378
    };
379
 
380
    hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
381
    futex_down(&fidx->lock);
382
    futex_up(&used_futex);
383
 
384
    return fidx;
385
}
386
 
387
fat_idx_t *
388
fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
389
{
390
    fat_idx_t *fidx;
391
    link_t *l;
392
    unsigned long pkey[] = {
393
        [UPH_DH_KEY] = dev_handle,
394
        [UPH_PFC_KEY] = pfc,
395
        [UPH_PDI_KEY] = pdi,
396
    };
397
 
398
    futex_down(&used_futex);
399
    l = hash_table_find(&up_hash, pkey);
400
    if (l) {
401
        fidx = hash_table_get_instance(l, fat_idx_t, uph_link);
402
    } else {
403
        fidx = fat_idx_create(dev_handle);
404
        if (!fidx) {
405
            futex_up(&used_futex);
406
            return NULL;
407
        }
408
 
409
        unsigned long ikey[] = {
410
            [UIH_DH_KEY] = dev_handle,
411
            [UIH_INDEX_KEY] = fidx->index,
412
        };
413
 
414
        fidx->pfc = pfc;
415
        fidx->pdi = pdi;
416
 
417
        hash_table_insert(&up_hash, pkey, &fidx->uph_link);
418
        hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
419
    }
420
    futex_down(&fidx->lock);
421
    futex_up(&used_futex);
422
 
423
    return fidx;
424
}
425
 
426
void fat_idx_hashin(fat_idx_t *idx)
427
{
428
    unsigned long pkey[] = {
429
        [UPH_DH_KEY] = idx->dev_handle,
430
        [UPH_PFC_KEY] = idx->pfc,
431
        [UPH_PDI_KEY] = idx->pdi,
432
    };
433
 
434
    futex_down(&used_futex);
435
    hash_table_insert(&up_hash, pkey, &idx->uph_link);
436
    futex_up(&used_futex);
437
}
438
 
439
void fat_idx_hashout(fat_idx_t *idx)
440
{
441
    unsigned long pkey[] = {
442
        [UPH_DH_KEY] = idx->dev_handle,
443
        [UPH_PFC_KEY] = idx->pfc,
444
        [UPH_PDI_KEY] = idx->pdi,
445
    };
446
 
447
    futex_down(&used_futex);
448
    hash_table_remove(&up_hash, pkey, 3);
449
    futex_up(&used_futex);
450
}
451
 
452
fat_idx_t *
453
fat_idx_get_by_index(dev_handle_t dev_handle, fs_index_t index)
454
{
455
    fat_idx_t *fidx = NULL;
456
    link_t *l;
457
    unsigned long ikey[] = {
458
        [UIH_DH_KEY] = dev_handle,
459
        [UIH_INDEX_KEY] = index,
460
    };
461
 
462
    futex_down(&used_futex);
463
    l = hash_table_find(&ui_hash, ikey);
464
    if (l) {
465
        fidx = hash_table_get_instance(l, fat_idx_t, uih_link);
466
        futex_down(&fidx->lock);
467
    }
468
    futex_up(&used_futex);
469
 
470
    return fidx;
471
}
472
 
473
/** Destroy the index structure.
474
 *
475
 * @param idx       The index structure to be destroyed.
476
 */
477
void fat_idx_destroy(fat_idx_t *idx)
478
{
479
    unsigned long ikey[] = {
480
        [UIH_DH_KEY] = idx->dev_handle,
481
        [UIH_INDEX_KEY] = idx->index,
482
    };
483
 
484
    assert(idx->pfc == FAT_CLST_RES0);
485
 
486
    futex_down(&used_futex);
487
    /*
488
     * Since we can only free unlinked nodes, the index structure is not
489
     * present in the position hash (uph). We therefore hash it out from
490
     * the index hash only.
491
     */
492
    hash_table_remove(&ui_hash, ikey, 2);
493
    futex_up(&used_futex);
494
    /* Release the VFS index. */
495
    fat_index_free(idx->dev_handle, idx->index);
496
    /* Deallocate the structure. */
497
    free(idx);
498
}
499
 
500
int fat_idx_init(void)
501
{
502
    if (!hash_table_create(&up_hash, UPH_BUCKETS, 3, &uph_ops))
503
        return ENOMEM;
504
    if (!hash_table_create(&ui_hash, UIH_BUCKETS, 2, &uih_ops)) {
505
        hash_table_destroy(&up_hash);
506
        return ENOMEM;
507
    }
508
    return EOK;
509
}
510
 
511
void fat_idx_fini(void)
512
{
513
    /* We assume the hash tables are empty. */
514
    hash_table_destroy(&up_hash);
515
    hash_table_destroy(&ui_hash);
516
}
517
 
518
int fat_idx_init_by_dev_handle(dev_handle_t dev_handle)
519
{
520
    unused_t *u;
521
    int rc = EOK;
522
 
523
    u = (unused_t *) malloc(sizeof(unused_t));
524
    if (!u)
525
        return ENOMEM;
526
    unused_initialize(u, dev_handle);
527
    futex_down(&unused_futex);
528
    if (!unused_find(dev_handle, false))
529
        list_append(&u->link, &unused_head);
530
    else
531
        rc = EEXIST;
532
    futex_up(&unused_futex);
533
    return rc;
534
}
535
 
536
void fat_idx_fini_by_dev_handle(dev_handle_t dev_handle)
537
{
538
    unused_t *u;
539
 
540
    u = unused_find(dev_handle, true);
541
    assert(u);
542
    list_remove(&u->link);
543
    futex_up(&unused_futex);
544
 
545
    while (!list_empty(&u->freed_head)) {
546
        freed_t *f;
547
        f = list_get_instance(u->freed_head.next, freed_t, link);
548
        list_remove(&f->link);
549
        free(f);
550
    }
551
    free(u);
552
}
553
 
554
/**
555
 * @}
556
 */