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