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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 */
3595 jermar 97
        b = block_get(dev_handle, rscnt + fsec, BLOCK_FLAGS_NONE);
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.
3595 jermar 117
 * @param flags     Flags passed to libblock.
3506 jermar 118
 *
3550 jermar 119
 * @return      Block structure holding the requested block.
3506 jermar 120
 */
3550 jermar 121
block_t *
122
_fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
3595 jermar 123
    bn_t bn, int flags)
3506 jermar 124
{
125
    block_t *b;
126
    unsigned bps;
127
    unsigned rscnt;     /* block address of the first FAT */
3550 jermar 128
    unsigned rde;
129
    unsigned rds;       /* root directory size */
130
    unsigned sf;
131
    unsigned ssa;       /* size of the system area */
132
    unsigned clusters, max_clusters;
3572 jermar 133
    fat_cluster_t lastc;
3506 jermar 134
 
3516 jermar 135
    bps = uint16_t_le2host(bs->bps);
136
    rscnt = uint16_t_le2host(bs->rscnt);
3550 jermar 137
    rde = uint16_t_le2host(bs->root_ent_max);
138
    sf = uint16_t_le2host(bs->sec_per_fat);
3506 jermar 139
 
3550 jermar 140
    rds = (sizeof(fat_dentry_t) * rde) / bps;
141
    rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
142
    ssa = rscnt + bs->fatcnt * sf + rds;
143
 
144
    if (firstc == FAT_CLST_ROOT) {
145
        /* root directory special case */
3571 jermar 146
        assert(bn < rds);
3595 jermar 147
        b = block_get(dev_handle, rscnt + bs->fatcnt * sf + bn, flags);
3550 jermar 148
        return b;
3506 jermar 149
    }
150
 
3571 jermar 151
    max_clusters = bn / bs->spc;
152
    clusters = fat_cluster_walk(bs, dev_handle, firstc, &lastc,
3550 jermar 153
        max_clusters);
154
    assert(clusters == max_clusters);
3506 jermar 155
 
3550 jermar 156
    b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
3595 jermar 157
        bn % bs->spc, flags);
3506 jermar 158
 
3550 jermar 159
    return b;
3506 jermar 160
}
161
 
162
/** Fill the gap between EOF and a new file position.
163
 *
3516 jermar 164
 * @param bs        Buffer holding the boot sector for nodep.
3506 jermar 165
 * @param nodep     FAT node with the gap.
166
 * @param mcl       First cluster in an independent cluster chain that will
167
 *          be later appended to the end of the node's own cluster
168
 *          chain. If pos is still in the last allocated cluster,
169
 *          this argument is ignored.
170
 * @param pos       Position in the last node block.
171
 */
3516 jermar 172
void fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, off_t pos)
3506 jermar 173
{
174
    uint16_t bps;
175
    unsigned spc;
3516 jermar 176
    block_t *b;
3506 jermar 177
    off_t o, boundary;
178
 
3516 jermar 179
    bps = uint16_t_le2host(bs->bps);
180
    spc = bs->spc;
3506 jermar 181
 
182
    boundary = ROUND_UP(nodep->size, bps * spc);
183
 
184
    /* zero out already allocated space */
3652 jermar 185
    for (o = nodep->size; o < pos && o < boundary;
3506 jermar 186
        o = ALIGN_DOWN(o + bps, bps)) {
3595 jermar 187
            int flags = (o % bps == 0) ?
188
            BLOCK_FLAGS_NOREAD : BLOCK_FLAGS_NONE;
189
        b = fat_block_get(bs, nodep, o / bps, flags);
3506 jermar 190
        memset(b->data + o % bps, 0, bps - o % bps);
191
        b->dirty = true;        /* need to sync node */
192
        block_put(b);
193
    }
194
 
195
    if (o >= pos)
196
        return;
197
 
198
    /* zero out the initial part of the new cluster chain */
199
    for (o = boundary; o < pos; o += bps) {
3516 jermar 200
        b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
3595 jermar 201
            (o - boundary) / bps, BLOCK_FLAGS_NOREAD);
3506 jermar 202
        memset(b->data, 0, min(bps, pos - o));
203
        b->dirty = true;        /* need to sync node */
204
        block_put(b);
205
    }
206
}
207
 
3572 jermar 208
/** Get cluster from the first FAT.
3518 jermar 209
 *
210
 * @param bs        Buffer holding the boot sector for the file system.
211
 * @param dev_handle    Device handle for the file system.
3572 jermar 212
 * @param clst      Cluster which to get.
213
 *
214
 * @return      Value found in the cluster.
215
 */
216
fat_cluster_t
217
fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst)
218
{
219
    block_t *b;
220
    uint16_t bps;
221
    uint16_t rscnt;
222
    fat_cluster_t *cp, value;
223
 
224
    bps = uint16_t_le2host(bs->bps);
225
    rscnt = uint16_t_le2host(bs->rscnt);
226
 
3595 jermar 227
    b = block_get(dev_handle, rscnt + (clst * sizeof(fat_cluster_t)) / bps,
228
        BLOCK_FLAGS_NONE);
3572 jermar 229
    cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
230
    value = uint16_t_le2host(*cp);
231
    block_put(b);
232
 
233
    return value;
234
}
235
 
236
/** Set cluster in one instance of FAT.
237
 *
238
 * @param bs        Buffer holding the boot sector for the file system.
239
 * @param dev_handle    Device handle for the file system.
3518 jermar 240
 * @param fatno     Number of the FAT instance where to make the change.
3572 jermar 241
 * @param clst      Cluster which is to be set.
242
 * @param value     Value to set the cluster with.
3518 jermar 243
 */
3506 jermar 244
void
3572 jermar 245
fat_set_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
3516 jermar 246
    fat_cluster_t clst, fat_cluster_t value)
3506 jermar 247
{
3516 jermar 248
    block_t *b;
3510 jermar 249
    uint16_t bps;
250
    uint16_t rscnt;
251
    uint16_t sf;
252
    fat_cluster_t *cp;
253
 
3516 jermar 254
    bps = uint16_t_le2host(bs->bps);
255
    rscnt = uint16_t_le2host(bs->rscnt);
256
    sf = uint16_t_le2host(bs->sec_per_fat);
3510 jermar 257
 
3516 jermar 258
    assert(fatno < bs->fatcnt);
259
    b = block_get(dev_handle, rscnt + sf * fatno +
3595 jermar 260
        (clst * sizeof(fat_cluster_t)) / bps, BLOCK_FLAGS_NONE);
3516 jermar 261
    cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
3510 jermar 262
    *cp = host2uint16_t_le(value);
3516 jermar 263
    b->dirty = true;        /* need to sync block */
264
    block_put(b);
3506 jermar 265
}
266
 
3518 jermar 267
/** Replay the allocatoin of clusters in all shadow instances of FAT.
268
 *
269
 * @param bs        Buffer holding the boot sector of the file system.
270
 * @param dev_handle    Device handle of the file system.
271
 * @param lifo      Chain of allocated clusters.
272
 * @param nclsts    Number of clusters in the lifo chain.
273
 */
3516 jermar 274
void fat_alloc_shadow_clusters(fat_bs_t *bs, dev_handle_t dev_handle,
275
    fat_cluster_t *lifo, unsigned nclsts)
3506 jermar 276
{
3507 jermar 277
    uint8_t fatno;
278
    unsigned c;
279
 
3516 jermar 280
    for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
3507 jermar 281
        for (c = 0; c < nclsts; c++) {
3572 jermar 282
            fat_set_cluster(bs, dev_handle, fatno, lifo[c],
3507 jermar 283
                c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
284
        }
285
    }
3506 jermar 286
}
287
 
3632 jermar 288
/** Allocate clusters in all copies of FAT.
3518 jermar 289
 *
290
 * This function will attempt to allocate the requested number of clusters in
3632 jermar 291
 * all instances of the FAT.  The FAT will be altered so that the allocated
3518 jermar 292
 * clusters form an independent chain (i.e. a chain which does not belong to any
293
 * file yet).
294
 *
295
 * @param bs        Buffer holding the boot sector of the file system.
296
 * @param dev_handle    Device handle of the file system.
297
 * @param nclsts    Number of clusters to allocate.
298
 * @param mcl       Output parameter where the first cluster in the chain
299
 *          will be returned.
300
 * @param lcl       Output parameter where the last cluster in the chain
301
 *          will be returned.
302
 *
303
 * @return      EOK on success, a negative error code otherwise.
304
 */
3506 jermar 305
int
3516 jermar 306
fat_alloc_clusters(fat_bs_t *bs, dev_handle_t dev_handle, unsigned nclsts,
307
    fat_cluster_t *mcl, fat_cluster_t *lcl)
3506 jermar 308
{
309
    uint16_t bps;
310
    uint16_t rscnt;
311
    uint16_t sf;
3516 jermar 312
    block_t *blk;
3506 jermar 313
    fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
314
    unsigned found = 0; /* top of the free cluster number stack */
315
    unsigned b, c, cl;
316
 
317
    lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
3632 jermar 318
    if (!lifo)
3506 jermar 319
        return ENOMEM;
320
 
3516 jermar 321
    bps = uint16_t_le2host(bs->bps);
322
    rscnt = uint16_t_le2host(bs->rscnt);
323
    sf = uint16_t_le2host(bs->sec_per_fat);
3506 jermar 324
 
325
    /*
326
     * Search FAT1 for unused clusters.
327
     */
3517 jermar 328
    futex_down(&fat_alloc_lock);
3632 jermar 329
    for (b = 0, cl = 0; b < sf; b++) {
330
        blk = block_get(dev_handle, rscnt + b, BLOCK_FLAGS_NONE);
3506 jermar 331
        for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
332
            fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
3512 jermar 333
            if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
3506 jermar 334
                /*
335
                 * The cluster is free. Put it into our stack
336
                 * of found clusters and mark it as non-free.
337
                 */
338
                lifo[found] = cl;
3512 jermar 339
                *clst = (found == 0) ?
340
                    host2uint16_t_le(FAT_CLST_LAST1) :
341
                    host2uint16_t_le(lifo[found - 1]);
3506 jermar 342
                blk->dirty = true;  /* need to sync block */
343
                if (++found == nclsts) {
344
                    /* we are almost done */
345
                    block_put(blk);
346
                    /* update the shadow copies of FAT */
3516 jermar 347
                    fat_alloc_shadow_clusters(bs,
348
                        dev_handle, lifo, nclsts);
3506 jermar 349
                    *mcl = lifo[found - 1];
350
                    *lcl = lifo[0];
351
                    free(lifo);
3517 jermar 352
                    futex_up(&fat_alloc_lock);
3506 jermar 353
                    return EOK;
354
                }
355
            }
356
        }
357
        block_put(blk);
358
    }
3517 jermar 359
    futex_up(&fat_alloc_lock);
3506 jermar 360
 
361
    /*
362
     * We could not find enough clusters. Now we need to free the clusters
363
     * we have allocated so far.
364
     */
3516 jermar 365
    while (found--) {
3572 jermar 366
        fat_set_cluster(bs, dev_handle, FAT1, lifo[found],
3516 jermar 367
            FAT_CLST_RES0);
368
    }
3506 jermar 369
 
370
    free(lifo);
371
    return ENOSPC;
372
}
373
 
3572 jermar 374
/** Free clusters forming a cluster chain in all copies of FAT.
375
 *
376
 * @param bs        Buffer hodling the boot sector of the file system.
377
 * @param dev_handle    Device handle of the file system.
378
 * @param firstc    First cluster in the chain which is to be freed.
379
 */
380
void
381
fat_free_clusters(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc)
382
{
383
    unsigned fatno;
384
    fat_cluster_t nextc;
385
 
386
    /* Mark all clusters in the chain as free in all copies of FAT. */
387
    while (firstc < FAT_CLST_LAST1) {
3637 jermar 388
        assert(firstc >= FAT_CLST_FIRST && firstc < FAT_CLST_BAD);
3572 jermar 389
        nextc = fat_get_cluster(bs, dev_handle, firstc);
390
        for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
391
            fat_set_cluster(bs, dev_handle, fatno, firstc,
392
                FAT_CLST_RES0);
393
        firstc = nextc;
394
    }
395
}
396
 
3518 jermar 397
/** Append a cluster chain to the last file cluster in all FATs.
398
 *
3572 jermar 399
 * @param bs        Buffer holding the boot sector of the file system.
3518 jermar 400
 * @param nodep     Node representing the file.
401
 * @param mcl       First cluster of the cluster chain to append.
402
 */
3516 jermar 403
void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
3506 jermar 404
{
3516 jermar 405
    dev_handle_t dev_handle = nodep->idx->dev_handle;
3513 jermar 406
    fat_cluster_t lcl;
3516 jermar 407
    uint8_t fatno;
3513 jermar 408
 
3572 jermar 409
    if (fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl,
3571 jermar 410
        (uint16_t) -1) == 0) {
3550 jermar 411
        /* No clusters allocated to the node yet. */
3656 jermar 412
        nodep->firstc = mcl;
3513 jermar 413
        nodep->dirty = true;        /* need to sync node */
414
        return;
415
    }
416
 
3516 jermar 417
    for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
3572 jermar 418
        fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
3506 jermar 419
}
420
 
3572 jermar 421
/** Chop off node clusters in all copies of FAT.
422
 *
423
 * @param bs        Buffer holding the boot sector of the file system.
424
 * @param nodep     FAT node where the chopping will take place.
425
 * @param lastc     Last cluster which will remain in the node. If this
426
 *          argument is FAT_CLST_RES0, then all clusters will
3573 jermar 427
 *          be chopped off.
3572 jermar 428
 */
429
void fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc)
430
{
431
    dev_handle_t dev_handle = nodep->idx->dev_handle;
432
    if (lastc == FAT_CLST_RES0) {
433
        /* The node will have zero size and no clusters allocated. */
434
        fat_free_clusters(bs, dev_handle, nodep->firstc);
435
        nodep->firstc = FAT_CLST_RES0;
436
        nodep->dirty = true;        /* need to sync node */
437
    } else {
438
        fat_cluster_t nextc;
439
        unsigned fatno;
440
 
441
        nextc = fat_get_cluster(bs, dev_handle, lastc);
442
 
443
        /* Terminate the cluster chain in all copies of FAT. */
444
        for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
445
            fat_set_cluster(bs, dev_handle, fatno, lastc, FAT_CLST_LAST1);
446
 
447
        /* Free all following clusters. */
448
        fat_free_clusters(bs, dev_handle, nextc);
449
    }
450
}
451
 
3504 jermar 452
/**
453
 * @}
454
 */