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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
 
2948 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
 
3153 svoboda 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
 
3009 svoboda 103
/** Futex protecting the up_hash and ui_hash. */
2948 svoboda 104
static futex_t used_futex = FUTEX_INITIALIZER;
105
 
2890 jermar 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;
2889 jermar 112
 
2890 jermar 113
#define UPH_BUCKETS_LOG 12
114
#define UPH_BUCKETS (1 << UPH_BUCKETS_LOG)
2889 jermar 115
 
2890 jermar 116
#define UPH_DH_KEY  0
117
#define UPH_PFC_KEY 1
118
#define UPH_PDI_KEY 2
2889 jermar 119
 
2890 jermar 120
static hash_index_t pos_hash(unsigned long key[])
2889 jermar 121
{
2890 jermar 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];
2889 jermar 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
     */
2890 jermar 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));
2889 jermar 144
 
145
    return h;
146
}
147
 
2890 jermar 148
static int pos_compare(unsigned long key[], hash_count_t keys, link_t *item)
2889 jermar 149
{
2890 jermar 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);
2889 jermar 154
 
155
    return (dev_handle == fidx->dev_handle) && (pfc == fidx->pfc) &&
156
        (pdi == fidx->pdi);
157
}
158
 
2890 jermar 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
 
2889 jermar 205
static void idx_remove_callback(link_t *item)
206
{
207
    /* nothing to do */
208
}
209
 
2890 jermar 210
static hash_table_operations_t uih_ops = {
2889 jermar 211
    .hash = idx_hash,
212
    .compare = idx_compare,
213
    .remove_callback = idx_remove_callback,
214
};
215
 
2881 jermar 216
/** Allocate a VFS index which is not currently in use. */
217
static bool fat_idx_alloc(dev_handle_t dev_handle, fs_index_t *index)
2876 jermar 218
{
2881 jermar 219
    unused_t *u;
220
 
221
    assert(index);
3153 svoboda 222
    u = unused_find(dev_handle, true);
223
    if (!u)
224
        return false;  
2881 jermar 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;
2948 svoboda 234
            futex_up(&unused_futex);
2881 jermar 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
        }
2948 svoboda 247
        futex_up(&unused_futex);
2881 jermar 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
     */
2948 svoboda 255
    futex_up(&unused_futex);
2881 jermar 256
    return false;
257
}
258
 
2884 jermar 259
/** If possible, coalesce two intervals of freed indices. */
260
static void try_coalesce_intervals(link_t *l, link_t *r, link_t *cur)
2881 jermar 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_idx_free(dev_handle_t dev_handle, fs_index_t index)
280
{
281
    unused_t *u;
282
 
3153 svoboda 283
    u = unused_find(dev_handle, true);
284
    assert(u);
2881 jermar 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)
2884 jermar 303
                    try_coalesce_intervals(lnk->prev, lnk,
2881 jermar 304
                        lnk);
2948 svoboda 305
                futex_up(&unused_futex);
2881 jermar 306
                return;
307
            }
308
            if (f->last == index - 1) {
309
                f->last++;
310
                if (lnk->next != &u->freed_head)
2884 jermar 311
                    try_coalesce_intervals(lnk, lnk->next,
2881 jermar 312
                        lnk);
2948 svoboda 313
                futex_up(&unused_futex);
2881 jermar 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);
2948 svoboda 324
                futex_up(&unused_futex);
2881 jermar 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
    }
2948 svoboda 338
    futex_up(&unused_futex);
2881 jermar 339
}
340
 
2890 jermar 341
fat_idx_t *
342
fat_idx_get_by_pos(dev_handle_t dev_handle, fat_cluster_t pfc, unsigned pdi)
2881 jermar 343
{
2889 jermar 344
    fat_idx_t *fidx;
345
    link_t *l;
2890 jermar 346
    unsigned long pkey[] = {
347
        [UPH_DH_KEY] = dev_handle,
348
        [UPH_PFC_KEY] = pfc,
349
        [UPH_PDI_KEY] = pdi,
2889 jermar 350
    };
351
 
2948 svoboda 352
    futex_down(&used_futex);
2890 jermar 353
    l = hash_table_find(&up_hash, pkey);
2889 jermar 354
    if (l) {
2890 jermar 355
        fidx = hash_table_get_instance(l, fat_idx_t, uph_link);
2889 jermar 356
    } else {
357
        fidx = (fat_idx_t *) malloc(sizeof(fat_idx_t));
358
        if (!fidx) {
3009 svoboda 359
            futex_up(&used_futex);
2889 jermar 360
            return NULL;
361
        }
362
        if (!fat_idx_alloc(dev_handle, &fidx->index)) {
363
            free(fidx);
3009 svoboda 364
            futex_up(&used_futex);
2889 jermar 365
            return NULL;
366
        }
2890 jermar 367
 
368
        unsigned long ikey[] = {
369
            [UIH_DH_KEY] = dev_handle,
370
            [UIH_INDEX_KEY] = fidx->index,
371
        };
372
 
373
        link_initialize(&fidx->uph_link);
374
        link_initialize(&fidx->uih_link);
3009 svoboda 375
        futex_initialize(&fidx->lock, 1);
2889 jermar 376
        fidx->dev_handle = dev_handle;
377
        fidx->pfc = pfc;
378
        fidx->pdi = pdi;
379
        fidx->nodep = NULL;
2890 jermar 380
 
381
        hash_table_insert(&up_hash, pkey, &fidx->uph_link);
382
        hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
2889 jermar 383
    }
3009 svoboda 384
    futex_down(&fidx->lock);
385
    futex_up(&used_futex);
2889 jermar 386
 
387
    return fidx;
2876 jermar 388
}
2889 jermar 389
 
2890 jermar 390
fat_idx_t *
391
fat_idx_get_by_index(dev_handle_t dev_handle, fs_index_t index)
392
{
393
    fat_idx_t *fidx = NULL;
394
    link_t *l;
395
    unsigned long ikey[] = {
396
        [UIH_DH_KEY] = dev_handle,
397
        [UIH_INDEX_KEY] = index,
398
    };
399
 
2948 svoboda 400
    futex_down(&used_futex);
2890 jermar 401
    l = hash_table_find(&ui_hash, ikey);
402
    if (l) {
403
        fidx = hash_table_get_instance(l, fat_idx_t, uih_link);
3009 svoboda 404
        futex_down(&fidx->lock);
2890 jermar 405
    }
3009 svoboda 406
    futex_up(&used_futex);
2890 jermar 407
 
408
    return fidx;
409
}
410
 
3153 svoboda 411
int fat_idx_init(void)
412
{
413
    if (!hash_table_create(&up_hash, UPH_BUCKETS, 3, &uph_ops))
414
        return ENOMEM;
415
    if (!hash_table_create(&ui_hash, UIH_BUCKETS, 2, &uih_ops)) {
416
        hash_table_destroy(&up_hash);
417
        return ENOMEM;
418
    }
419
    return EOK;
420
}
421
 
422
void fat_idx_fini(void)
423
{
424
    /* We assume the hash tables are empty. */
425
    hash_table_destroy(&up_hash);
426
    hash_table_destroy(&ui_hash);
427
}
428
 
429
int fat_idx_init_by_dev_handle(dev_handle_t dev_handle)
430
{
431
    unused_t *u;
432
    int rc = EOK;
433
 
434
    u = (unused_t *) malloc(sizeof(unused_t));
435
    if (!u)
436
        return ENOMEM;
437
    unused_initialize(u, dev_handle);
438
    futex_down(&unused_futex);
439
    if (!unused_find(dev_handle, false))
440
        list_append(&u->link, &unused_head);
441
    else
442
        rc = EEXIST;
443
    futex_up(&unused_futex);
444
    return rc;
445
}
446
 
447
void fat_idx_fini_by_dev_handle(dev_handle_t dev_handle)
448
{
449
    unused_t *u;
450
 
451
    u = unused_find(dev_handle, true);
452
    assert(u);
453
    list_remove(&u->link);
454
    futex_up(&unused_futex);
455
 
456
    while (!list_empty(&u->freed_head)) {
457
        freed_t *f;
458
        f = list_get_instance(u->freed_head.next, freed_t, link);
459
        list_remove(&f->link);
460
        free(f);
461
    }
462
    free(u);
463
}
464
 
465
/**
466
 * @}
467
 */