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3504 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_fat.c
3517 jermar 35
 * @brief   Functions that manipulate the File Allocation Tables.
3504 jermar 36
 */
37
 
3506 jermar 38
#include "fat_fat.h"
39
#include "fat_dentry.h"
40
#include "fat.h"
41
#include "../../vfs/vfs.h"
42
#include <libfs.h>
3521 jermar 43
#include <libblock.h>
3506 jermar 44
#include <errno.h>
45
#include <byteorder.h>
46
#include <align.h>
47
#include <assert.h>
3517 jermar 48
#include <futex.h>
3504 jermar 49
 
3517 jermar 50
/**
51
 * The fat_alloc_lock futex protects all copies of the File Allocation Table
52
 * during allocation of clusters. The lock does not have to be held durring
53
 * deallocation of clusters.
54
 */  
55
static futex_t fat_alloc_lock = FUTEX_INITIALIZER;
56
 
3550 jermar 57
/** Walk the cluster chain.
3518 jermar 58
 *
3550 jermar 59
 * @param bs        Buffer holding the boot sector for the file.
60
 * @param dev_handle    Device handle of the device with the file.
61
 * @param firstc    First cluster to start the walk with.
3571 jermar 62
 * @param lastc     If non-NULL, output argument hodling the last cluster number visited.
3550 jermar 63
 * @param max_clusters  Maximum number of clusters to visit.   
3518 jermar 64
 *
3550 jermar 65
 * @return      Number of clusters seen during the walk.
3518 jermar 66
 */
3550 jermar 67
uint16_t
68
fat_cluster_walk(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
3571 jermar 69
    fat_cluster_t *lastc, uint16_t max_clusters)
3506 jermar 70
{
71
    block_t *b;
72
    unsigned bps;
73
    unsigned rscnt;     /* block address of the first FAT */
3550 jermar 74
    uint16_t clusters = 0;
3506 jermar 75
    fat_cluster_t clst = firstc;
76
 
3516 jermar 77
    bps = uint16_t_le2host(bs->bps);
78
    rscnt = uint16_t_le2host(bs->rscnt);
3506 jermar 79
 
3550 jermar 80
    if (firstc == FAT_CLST_RES0) {
81
        /* No space allocated to the file. */
3571 jermar 82
        if (lastc)
83
            *lastc = firstc;
3550 jermar 84
        return 0;
3506 jermar 85
    }
86
 
3550 jermar 87
    while (clst < FAT_CLST_LAST1 && clusters < max_clusters) {
3571 jermar 88
        bn_t fsec;  /* sector offset relative to FAT1 */
3506 jermar 89
        unsigned fidx;  /* FAT1 entry index */
90
 
3550 jermar 91
        assert(clst >= FAT_CLST_FIRST);
3571 jermar 92
        if (lastc)
93
            *lastc = clst;  /* remember the last cluster number */
3506 jermar 94
        fsec = (clst * sizeof(fat_cluster_t)) / bps;
95
        fidx = clst % (bps / sizeof(fat_cluster_t));
96
        /* read FAT1 */
3542 jermar 97
        b = block_get(dev_handle, rscnt + fsec);
3506 jermar 98
        clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
99
        assert(clst != FAT_CLST_BAD);
100
        block_put(b);
3550 jermar 101
        clusters++;
3506 jermar 102
    }
103
 
3571 jermar 104
    if (lastc && clst < FAT_CLST_LAST1)
105
        *lastc = clst;
3506 jermar 106
 
3550 jermar 107
    return clusters;
3506 jermar 108
}
109
 
3550 jermar 110
/** Read block from file located on a FAT file system.
3506 jermar 111
 *
3550 jermar 112
 * @param bs        Buffer holding the boot sector of the file system.
113
 * @param dev_handle    Device handle of the file system.
114
 * @param firstc    First cluster used by the file. Can be zero if the file
115
 *          is empty.
3571 jermar 116
 * @param bn        Block number.
3506 jermar 117
 *
3550 jermar 118
 * @return      Block structure holding the requested block.
3506 jermar 119
 */
3550 jermar 120
block_t *
121
_fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
3571 jermar 122
    bn_t bn)
3506 jermar 123
{
124
    block_t *b;
125
    unsigned bps;
126
    unsigned rscnt;     /* block address of the first FAT */
3550 jermar 127
    unsigned rde;
128
    unsigned rds;       /* root directory size */
129
    unsigned sf;
130
    unsigned ssa;       /* size of the system area */
131
    unsigned clusters, max_clusters;
3572 jermar 132
    fat_cluster_t lastc;
3506 jermar 133
 
3516 jermar 134
    bps = uint16_t_le2host(bs->bps);
135
    rscnt = uint16_t_le2host(bs->rscnt);
3550 jermar 136
    rde = uint16_t_le2host(bs->root_ent_max);
137
    sf = uint16_t_le2host(bs->sec_per_fat);
3506 jermar 138
 
3550 jermar 139
    rds = (sizeof(fat_dentry_t) * rde) / bps;
140
    rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
141
    ssa = rscnt + bs->fatcnt * sf + rds;
142
 
143
    if (firstc == FAT_CLST_ROOT) {
144
        /* root directory special case */
3571 jermar 145
        assert(bn < rds);
146
        b = block_get(dev_handle, rscnt + bs->fatcnt * sf + bn);
3550 jermar 147
        return b;
3506 jermar 148
    }
149
 
3571 jermar 150
    max_clusters = bn / bs->spc;
151
    clusters = fat_cluster_walk(bs, dev_handle, firstc, &lastc,
3550 jermar 152
        max_clusters);
153
    assert(clusters == max_clusters);
3506 jermar 154
 
3550 jermar 155
    b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
3571 jermar 156
        bn % bs->spc);
3506 jermar 157
 
3550 jermar 158
    return b;
3506 jermar 159
}
160
 
161
/** Fill the gap between EOF and a new file position.
162
 *
3516 jermar 163
 * @param bs        Buffer holding the boot sector for nodep.
3506 jermar 164
 * @param nodep     FAT node with the gap.
165
 * @param mcl       First cluster in an independent cluster chain that will
166
 *          be later appended to the end of the node's own cluster
167
 *          chain. If pos is still in the last allocated cluster,
168
 *          this argument is ignored.
169
 * @param pos       Position in the last node block.
170
 */
3516 jermar 171
void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
3506 jermar 172
{
173
    uint16_t bps;
174
    unsigned spc;
3516 jermar 175
    block_t *b;
3506 jermar 176
    off_t o, boundary;
177
 
3516 jermar 178
    bps = uint16_t_le2host(bs->bps);
179
    spc = bs->spc;
3506 jermar 180
 
181
    boundary = ROUND_UP(nodep->size, bps * spc);
182
 
183
    /* zero out already allocated space */
184
    for (o = nodep->size - 1; o < pos && o < boundary;
185
        o = ALIGN_DOWN(o + bps, bps)) {
3516 jermar 186
        b = fat_block_get(bs, nodep, o / bps);
3506 jermar 187
        memset(b->data + o % bps, 0, bps - o % bps);
188
        b->dirty = true;        /* need to sync node */
189
        block_put(b);
190
    }
191
 
192
    if (o >= pos)
193
        return;
194
 
195
    /* zero out the initial part of the new cluster chain */
196
    for (o = boundary; o < pos; o += bps) {
3516 jermar 197
        b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
3506 jermar 198
            (o - boundary) / bps);
199
        memset(b->data, 0, min(bps, pos - o));
200
        b->dirty = true;        /* need to sync node */
201
        block_put(b);
202
    }
203
}
204
 
3572 jermar 205
/** Get cluster from the first FAT.
3518 jermar 206
 *
207
 * @param bs        Buffer holding the boot sector for the file system.
208
 * @param dev_handle    Device handle for the file system.
3572 jermar 209
 * @param clst      Cluster which to get.
210
 *
211
 * @return      Value found in the cluster.
212
 */
213
fat_cluster_t
214
fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst)
215
{
216
    block_t *b;
217
    uint16_t bps;
218
    uint16_t rscnt;
219
    fat_cluster_t *cp, value;
220
 
221
    bps = uint16_t_le2host(bs->bps);
222
    rscnt = uint16_t_le2host(bs->rscnt);
223
 
224
    b = block_get(dev_handle, rscnt + (clst * sizeof(fat_cluster_t)) / bps);
225
    cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
226
    value = uint16_t_le2host(*cp);
227
    block_put(b);
228
 
229
    return value;
230
}
231
 
232
/** Set cluster in one instance of FAT.
233
 *
234
 * @param bs        Buffer holding the boot sector for the file system.
235
 * @param dev_handle    Device handle for the file system.
3518 jermar 236
 * @param fatno     Number of the FAT instance where to make the change.
3572 jermar 237
 * @param clst      Cluster which is to be set.
238
 * @param value     Value to set the cluster with.
3518 jermar 239
 */
3506 jermar 240
void
3572 jermar 241
fat_set_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
3516 jermar 242
    fat_cluster_t clst, fat_cluster_t value)
3506 jermar 243
{
3516 jermar 244
    block_t *b;
3510 jermar 245
    uint16_t bps;
246
    uint16_t rscnt;
247
    uint16_t sf;
248
    fat_cluster_t *cp;
249
 
3516 jermar 250
    bps = uint16_t_le2host(bs->bps);
251
    rscnt = uint16_t_le2host(bs->rscnt);
252
    sf = uint16_t_le2host(bs->sec_per_fat);
3510 jermar 253
 
3516 jermar 254
    assert(fatno < bs->fatcnt);
255
    b = block_get(dev_handle, rscnt + sf * fatno +
3542 jermar 256
        (clst * sizeof(fat_cluster_t)) / bps);
3516 jermar 257
    cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
3510 jermar 258
    *cp = host2uint16_t_le(value);
3516 jermar 259
    b->dirty = true;        /* need to sync block */
260
    block_put(b);
3506 jermar 261
}
262
 
3518 jermar 263
/** Replay the allocatoin of clusters in all shadow instances of FAT.
264
 *
265
 * @param bs        Buffer holding the boot sector of the file system.
266
 * @param dev_handle    Device handle of the file system.
267
 * @param lifo      Chain of allocated clusters.
268
 * @param nclsts    Number of clusters in the lifo chain.
269
 */
3516 jermar 270
void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle,
271
    fat_cluster_t *lifo, unsigned nclsts)
3506 jermar 272
{
3507 jermar 273
    uint8_t fatno;
274
    unsigned c;
275
 
3516 jermar 276
    for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
3507 jermar 277
        for (c = 0; c < nclsts; c++) {
3572 jermar 278
            fat_set_cluster(bs, dev_handle, fatno, lifo[c],
3507 jermar 279
                c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
280
        }
281
    }
3506 jermar 282
}
283
 
3518 jermar 284
/** Allocate clusters in FAT1.
285
 *
286
 * This function will attempt to allocate the requested number of clusters in
287
 * the first FAT instance.  The FAT will be altered so that the allocated
288
 * clusters form an independent chain (i.e. a chain which does not belong to any
289
 * file yet).
290
 *
291
 * @param bs        Buffer holding the boot sector of the file system.
292
 * @param dev_handle    Device handle of the file system.
293
 * @param nclsts    Number of clusters to allocate.
294
 * @param mcl       Output parameter where the first cluster in the chain
295
 *          will be returned.
296
 * @param lcl       Output parameter where the last cluster in the chain
297
 *          will be returned.
298
 *
299
 * @return      EOK on success, a negative error code otherwise.
300
 */
3506 jermar 301
int
3516 jermar 302
fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts,
303
    fat_cluster_t *mcl, fat_cluster_t *lcl)
3506 jermar 304
{
305
    uint16_t bps;
306
    uint16_t rscnt;
307
    uint16_t sf;
3516 jermar 308
    block_t *blk;
3506 jermar 309
    fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
310
    unsigned found = 0; /* top of the free cluster number stack */
311
    unsigned b, c, cl;
312
 
313
    lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
314
    if (lifo)
315
        return ENOMEM;
316
 
3516 jermar 317
    bps = uint16_t_le2host(bs->bps);
318
    rscnt = uint16_t_le2host(bs->rscnt);
319
    sf = uint16_t_le2host(bs->sec_per_fat);
3506 jermar 320
 
321
    /*
322
     * Search FAT1 for unused clusters.
323
     */
3517 jermar 324
    futex_down(&fat_alloc_lock);
3506 jermar 325
    for (b = 0, cl = 0; b < sf; blk++) {
3542 jermar 326
        blk = block_get(dev_handle, rscnt + b);
3506 jermar 327
        for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
328
            fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
3512 jermar 329
            if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
3506 jermar 330
                /*
331
                 * The cluster is free. Put it into our stack
332
                 * of found clusters and mark it as non-free.
333
                 */
334
                lifo[found] = cl;
3512 jermar 335
                *clst = (found == 0) ?
336
                    host2uint16_t_le(FAT_CLST_LAST1) :
337
                    host2uint16_t_le(lifo[found - 1]);
3506 jermar 338
                blk->dirty = true;  /* need to sync block */
339
                if (++found == nclsts) {
340
                    /* we are almost done */
341
                    block_put(blk);
342
                    /* update the shadow copies of FAT */
3516 jermar 343
                    fat_alloc_shadow_clusters(bs,
344
                        dev_handle, lifo, nclsts);
3506 jermar 345
                    *mcl = lifo[found - 1];
346
                    *lcl = lifo[0];
347
                    free(lifo);
3517 jermar 348
                    futex_up(&fat_alloc_lock);
3506 jermar 349
                    return EOK;
350
                }
351
            }
352
        }
353
        block_put(blk);
354
    }
3517 jermar 355
    futex_up(&fat_alloc_lock);
3506 jermar 356
 
357
    /*
358
     * We could not find enough clusters. Now we need to free the clusters
359
     * we have allocated so far.
360
     */
3516 jermar 361
    while (found--) {
3572 jermar 362
        fat_set_cluster(bs, dev_handle, FAT1, lifo[found],
3516 jermar 363
            FAT_CLST_RES0);
364
    }
3506 jermar 365
 
366
    free(lifo);
367
    return ENOSPC;
368
}
369
 
3572 jermar 370
/** Free clusters forming a cluster chain in all copies of FAT.
371
 *
372
 * @param bs        Buffer hodling the boot sector of the file system.
373
 * @param dev_handle    Device handle of the file system.
374
 * @param firstc    First cluster in the chain which is to be freed.
375
 */
376
void
377
fat_free_clusters(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc)
378
{
379
    unsigned fatno;
380
    fat_cluster_t nextc;
381
 
382
    /* Mark all clusters in the chain as free in all copies of FAT. */
383
    while (firstc < FAT_CLST_LAST1) {
384
        nextc = fat_get_cluster(bs, dev_handle, firstc);
385
        assert(nextc >= FAT_CLST_FIRST && nextc < FAT_CLST_BAD);
386
        for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
387
            fat_set_cluster(bs, dev_handle, fatno, firstc,
388
                FAT_CLST_RES0);
389
        firstc = nextc;
390
    }
391
}
392
 
3518 jermar 393
/** Append a cluster chain to the last file cluster in all FATs.
394
 *
3572 jermar 395
 * @param bs        Buffer holding the boot sector of the file system.
3518 jermar 396
 * @param nodep     Node representing the file.
397
 * @param mcl       First cluster of the cluster chain to append.
398
 */
3516 jermar 399
void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
3506 jermar 400
{
3516 jermar 401
    dev_handle_t dev_handle = nodep->idx->dev_handle;
3513 jermar 402
    fat_cluster_t lcl;
3516 jermar 403
    uint8_t fatno;
3513 jermar 404
 
3572 jermar 405
    if (fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl,
3571 jermar 406
        (uint16_t) -1) == 0) {
3550 jermar 407
        /* No clusters allocated to the node yet. */
3513 jermar 408
        nodep->firstc = host2uint16_t_le(mcl);
409
        nodep->dirty = true;        /* need to sync node */
410
        return;
411
    }
412
 
3516 jermar 413
    for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
3572 jermar 414
        fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
3506 jermar 415
}
416
 
3572 jermar 417
/** Chop off node clusters in all copies of FAT.
418
 *
419
 * @param bs        Buffer holding the boot sector of the file system.
420
 * @param nodep     FAT node where the chopping will take place.
421
 * @param lastc     Last cluster which will remain in the node. If this
422
 *          argument is FAT_CLST_RES0, then all clusters will
3573 jermar 423
 *          be chopped off.
3572 jermar 424
 */
425
void fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc)
426
{
427
    dev_handle_t dev_handle = nodep->idx->dev_handle;
428
    if (lastc == FAT_CLST_RES0) {
429
        /* The node will have zero size and no clusters allocated. */
430
        fat_free_clusters(bs, dev_handle, nodep->firstc);
431
        nodep->firstc = FAT_CLST_RES0;
432
        nodep->dirty = true;        /* need to sync node */
433
    } else {
434
        fat_cluster_t nextc;
435
        unsigned fatno;
436
 
437
        nextc = fat_get_cluster(bs, dev_handle, lastc);
438
 
439
        /* Terminate the cluster chain in all copies of FAT. */
440
        for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
441
            fat_set_cluster(bs, dev_handle, fatno, lastc, FAT_CLST_LAST1);
442
 
443
        /* Free all following clusters. */
444
        fat_free_clusters(bs, dev_handle, nextc);
445
    }
446
}
447
 
3504 jermar 448
/**
449
 * @}
450
 */