xref: /openbmc/linux/fs/fat/fatent.c (revision 09c434b8)
1  /*
2   * Copyright (C) 2004, OGAWA Hirofumi
3   * Released under GPL v2.
4   */
5  
6  #include <linux/blkdev.h>
7  #include <linux/sched/signal.h>
8  #include "fat.h"
9  
10  struct fatent_operations {
11  	void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
12  	void (*ent_set_ptr)(struct fat_entry *, int);
13  	int (*ent_bread)(struct super_block *, struct fat_entry *,
14  			 int, sector_t);
15  	int (*ent_get)(struct fat_entry *);
16  	void (*ent_put)(struct fat_entry *, int);
17  	int (*ent_next)(struct fat_entry *);
18  };
19  
20  static DEFINE_SPINLOCK(fat12_entry_lock);
21  
22  static void fat12_ent_blocknr(struct super_block *sb, int entry,
23  			      int *offset, sector_t *blocknr)
24  {
25  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
26  	int bytes = entry + (entry >> 1);
27  	WARN_ON(!fat_valid_entry(sbi, entry));
28  	*offset = bytes & (sb->s_blocksize - 1);
29  	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
30  }
31  
32  static void fat_ent_blocknr(struct super_block *sb, int entry,
33  			    int *offset, sector_t *blocknr)
34  {
35  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
36  	int bytes = (entry << sbi->fatent_shift);
37  	WARN_ON(!fat_valid_entry(sbi, entry));
38  	*offset = bytes & (sb->s_blocksize - 1);
39  	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
40  }
41  
42  static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
43  {
44  	struct buffer_head **bhs = fatent->bhs;
45  	if (fatent->nr_bhs == 1) {
46  		WARN_ON(offset >= (bhs[0]->b_size - 1));
47  		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
48  		fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
49  	} else {
50  		WARN_ON(offset != (bhs[0]->b_size - 1));
51  		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
52  		fatent->u.ent12_p[1] = bhs[1]->b_data;
53  	}
54  }
55  
56  static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
57  {
58  	WARN_ON(offset & (2 - 1));
59  	fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
60  }
61  
62  static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
63  {
64  	WARN_ON(offset & (4 - 1));
65  	fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
66  }
67  
68  static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
69  			   int offset, sector_t blocknr)
70  {
71  	struct buffer_head **bhs = fatent->bhs;
72  
73  	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
74  	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
75  
76  	bhs[0] = sb_bread(sb, blocknr);
77  	if (!bhs[0])
78  		goto err;
79  
80  	if ((offset + 1) < sb->s_blocksize)
81  		fatent->nr_bhs = 1;
82  	else {
83  		/* This entry is block boundary, it needs the next block */
84  		blocknr++;
85  		bhs[1] = sb_bread(sb, blocknr);
86  		if (!bhs[1])
87  			goto err_brelse;
88  		fatent->nr_bhs = 2;
89  	}
90  	fat12_ent_set_ptr(fatent, offset);
91  	return 0;
92  
93  err_brelse:
94  	brelse(bhs[0]);
95  err:
96  	fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
97  	return -EIO;
98  }
99  
100  static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
101  			 int offset, sector_t blocknr)
102  {
103  	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
104  
105  	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
106  	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
107  	fatent->bhs[0] = sb_bread(sb, blocknr);
108  	if (!fatent->bhs[0]) {
109  		fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
110  		       (llu)blocknr);
111  		return -EIO;
112  	}
113  	fatent->nr_bhs = 1;
114  	ops->ent_set_ptr(fatent, offset);
115  	return 0;
116  }
117  
118  static int fat12_ent_get(struct fat_entry *fatent)
119  {
120  	u8 **ent12_p = fatent->u.ent12_p;
121  	int next;
122  
123  	spin_lock(&fat12_entry_lock);
124  	if (fatent->entry & 1)
125  		next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
126  	else
127  		next = (*ent12_p[1] << 8) | *ent12_p[0];
128  	spin_unlock(&fat12_entry_lock);
129  
130  	next &= 0x0fff;
131  	if (next >= BAD_FAT12)
132  		next = FAT_ENT_EOF;
133  	return next;
134  }
135  
136  static int fat16_ent_get(struct fat_entry *fatent)
137  {
138  	int next = le16_to_cpu(*fatent->u.ent16_p);
139  	WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
140  	if (next >= BAD_FAT16)
141  		next = FAT_ENT_EOF;
142  	return next;
143  }
144  
145  static int fat32_ent_get(struct fat_entry *fatent)
146  {
147  	int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
148  	WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
149  	if (next >= BAD_FAT32)
150  		next = FAT_ENT_EOF;
151  	return next;
152  }
153  
154  static void fat12_ent_put(struct fat_entry *fatent, int new)
155  {
156  	u8 **ent12_p = fatent->u.ent12_p;
157  
158  	if (new == FAT_ENT_EOF)
159  		new = EOF_FAT12;
160  
161  	spin_lock(&fat12_entry_lock);
162  	if (fatent->entry & 1) {
163  		*ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
164  		*ent12_p[1] = new >> 4;
165  	} else {
166  		*ent12_p[0] = new & 0xff;
167  		*ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
168  	}
169  	spin_unlock(&fat12_entry_lock);
170  
171  	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
172  	if (fatent->nr_bhs == 2)
173  		mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
174  }
175  
176  static void fat16_ent_put(struct fat_entry *fatent, int new)
177  {
178  	if (new == FAT_ENT_EOF)
179  		new = EOF_FAT16;
180  
181  	*fatent->u.ent16_p = cpu_to_le16(new);
182  	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
183  }
184  
185  static void fat32_ent_put(struct fat_entry *fatent, int new)
186  {
187  	WARN_ON(new & 0xf0000000);
188  	new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
189  	*fatent->u.ent32_p = cpu_to_le32(new);
190  	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
191  }
192  
193  static int fat12_ent_next(struct fat_entry *fatent)
194  {
195  	u8 **ent12_p = fatent->u.ent12_p;
196  	struct buffer_head **bhs = fatent->bhs;
197  	u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
198  
199  	fatent->entry++;
200  	if (fatent->nr_bhs == 1) {
201  		WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
202  							(bhs[0]->b_size - 2)));
203  		WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
204  							(bhs[0]->b_size - 1)));
205  		if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
206  			ent12_p[0] = nextp - 1;
207  			ent12_p[1] = nextp;
208  			return 1;
209  		}
210  	} else {
211  		WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
212  							(bhs[0]->b_size - 1)));
213  		WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
214  		ent12_p[0] = nextp - 1;
215  		ent12_p[1] = nextp;
216  		brelse(bhs[0]);
217  		bhs[0] = bhs[1];
218  		fatent->nr_bhs = 1;
219  		return 1;
220  	}
221  	ent12_p[0] = NULL;
222  	ent12_p[1] = NULL;
223  	return 0;
224  }
225  
226  static int fat16_ent_next(struct fat_entry *fatent)
227  {
228  	const struct buffer_head *bh = fatent->bhs[0];
229  	fatent->entry++;
230  	if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
231  		fatent->u.ent16_p++;
232  		return 1;
233  	}
234  	fatent->u.ent16_p = NULL;
235  	return 0;
236  }
237  
238  static int fat32_ent_next(struct fat_entry *fatent)
239  {
240  	const struct buffer_head *bh = fatent->bhs[0];
241  	fatent->entry++;
242  	if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
243  		fatent->u.ent32_p++;
244  		return 1;
245  	}
246  	fatent->u.ent32_p = NULL;
247  	return 0;
248  }
249  
250  static const struct fatent_operations fat12_ops = {
251  	.ent_blocknr	= fat12_ent_blocknr,
252  	.ent_set_ptr	= fat12_ent_set_ptr,
253  	.ent_bread	= fat12_ent_bread,
254  	.ent_get	= fat12_ent_get,
255  	.ent_put	= fat12_ent_put,
256  	.ent_next	= fat12_ent_next,
257  };
258  
259  static const struct fatent_operations fat16_ops = {
260  	.ent_blocknr	= fat_ent_blocknr,
261  	.ent_set_ptr	= fat16_ent_set_ptr,
262  	.ent_bread	= fat_ent_bread,
263  	.ent_get	= fat16_ent_get,
264  	.ent_put	= fat16_ent_put,
265  	.ent_next	= fat16_ent_next,
266  };
267  
268  static const struct fatent_operations fat32_ops = {
269  	.ent_blocknr	= fat_ent_blocknr,
270  	.ent_set_ptr	= fat32_ent_set_ptr,
271  	.ent_bread	= fat_ent_bread,
272  	.ent_get	= fat32_ent_get,
273  	.ent_put	= fat32_ent_put,
274  	.ent_next	= fat32_ent_next,
275  };
276  
277  static inline void lock_fat(struct msdos_sb_info *sbi)
278  {
279  	mutex_lock(&sbi->fat_lock);
280  }
281  
282  static inline void unlock_fat(struct msdos_sb_info *sbi)
283  {
284  	mutex_unlock(&sbi->fat_lock);
285  }
286  
287  void fat_ent_access_init(struct super_block *sb)
288  {
289  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
290  
291  	mutex_init(&sbi->fat_lock);
292  
293  	if (is_fat32(sbi)) {
294  		sbi->fatent_shift = 2;
295  		sbi->fatent_ops = &fat32_ops;
296  	} else if (is_fat16(sbi)) {
297  		sbi->fatent_shift = 1;
298  		sbi->fatent_ops = &fat16_ops;
299  	} else if (is_fat12(sbi)) {
300  		sbi->fatent_shift = -1;
301  		sbi->fatent_ops = &fat12_ops;
302  	} else {
303  		fat_fs_error(sb, "invalid FAT variant, %u bits", sbi->fat_bits);
304  	}
305  }
306  
307  static void mark_fsinfo_dirty(struct super_block *sb)
308  {
309  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
310  
311  	if (sb_rdonly(sb) || !is_fat32(sbi))
312  		return;
313  
314  	__mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
315  }
316  
317  static inline int fat_ent_update_ptr(struct super_block *sb,
318  				     struct fat_entry *fatent,
319  				     int offset, sector_t blocknr)
320  {
321  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
322  	const struct fatent_operations *ops = sbi->fatent_ops;
323  	struct buffer_head **bhs = fatent->bhs;
324  
325  	/* Is this fatent's blocks including this entry? */
326  	if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
327  		return 0;
328  	if (is_fat12(sbi)) {
329  		if ((offset + 1) < sb->s_blocksize) {
330  			/* This entry is on bhs[0]. */
331  			if (fatent->nr_bhs == 2) {
332  				brelse(bhs[1]);
333  				fatent->nr_bhs = 1;
334  			}
335  		} else {
336  			/* This entry needs the next block. */
337  			if (fatent->nr_bhs != 2)
338  				return 0;
339  			if (bhs[1]->b_blocknr != (blocknr + 1))
340  				return 0;
341  		}
342  	}
343  	ops->ent_set_ptr(fatent, offset);
344  	return 1;
345  }
346  
347  int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
348  {
349  	struct super_block *sb = inode->i_sb;
350  	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
351  	const struct fatent_operations *ops = sbi->fatent_ops;
352  	int err, offset;
353  	sector_t blocknr;
354  
355  	if (!fat_valid_entry(sbi, entry)) {
356  		fatent_brelse(fatent);
357  		fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
358  		return -EIO;
359  	}
360  
361  	fatent_set_entry(fatent, entry);
362  	ops->ent_blocknr(sb, entry, &offset, &blocknr);
363  
364  	if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
365  		fatent_brelse(fatent);
366  		err = ops->ent_bread(sb, fatent, offset, blocknr);
367  		if (err)
368  			return err;
369  	}
370  	return ops->ent_get(fatent);
371  }
372  
373  /* FIXME: We can write the blocks as more big chunk. */
374  static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
375  			  int nr_bhs)
376  {
377  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
378  	struct buffer_head *c_bh;
379  	int err, n, copy;
380  
381  	err = 0;
382  	for (copy = 1; copy < sbi->fats; copy++) {
383  		sector_t backup_fat = sbi->fat_length * copy;
384  
385  		for (n = 0; n < nr_bhs; n++) {
386  			c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
387  			if (!c_bh) {
388  				err = -ENOMEM;
389  				goto error;
390  			}
391  			memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
392  			set_buffer_uptodate(c_bh);
393  			mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
394  			if (sb->s_flags & SB_SYNCHRONOUS)
395  				err = sync_dirty_buffer(c_bh);
396  			brelse(c_bh);
397  			if (err)
398  				goto error;
399  		}
400  	}
401  error:
402  	return err;
403  }
404  
405  int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
406  		  int new, int wait)
407  {
408  	struct super_block *sb = inode->i_sb;
409  	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
410  	int err;
411  
412  	ops->ent_put(fatent, new);
413  	if (wait) {
414  		err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
415  		if (err)
416  			return err;
417  	}
418  	return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
419  }
420  
421  static inline int fat_ent_next(struct msdos_sb_info *sbi,
422  			       struct fat_entry *fatent)
423  {
424  	if (sbi->fatent_ops->ent_next(fatent)) {
425  		if (fatent->entry < sbi->max_cluster)
426  			return 1;
427  	}
428  	return 0;
429  }
430  
431  static inline int fat_ent_read_block(struct super_block *sb,
432  				     struct fat_entry *fatent)
433  {
434  	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
435  	sector_t blocknr;
436  	int offset;
437  
438  	fatent_brelse(fatent);
439  	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
440  	return ops->ent_bread(sb, fatent, offset, blocknr);
441  }
442  
443  static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
444  			    struct fat_entry *fatent)
445  {
446  	int n, i;
447  
448  	for (n = 0; n < fatent->nr_bhs; n++) {
449  		for (i = 0; i < *nr_bhs; i++) {
450  			if (fatent->bhs[n] == bhs[i])
451  				break;
452  		}
453  		if (i == *nr_bhs) {
454  			get_bh(fatent->bhs[n]);
455  			bhs[i] = fatent->bhs[n];
456  			(*nr_bhs)++;
457  		}
458  	}
459  }
460  
461  int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
462  {
463  	struct super_block *sb = inode->i_sb;
464  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
465  	const struct fatent_operations *ops = sbi->fatent_ops;
466  	struct fat_entry fatent, prev_ent;
467  	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
468  	int i, count, err, nr_bhs, idx_clus;
469  
470  	BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));	/* fixed limit */
471  
472  	lock_fat(sbi);
473  	if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
474  	    sbi->free_clusters < nr_cluster) {
475  		unlock_fat(sbi);
476  		return -ENOSPC;
477  	}
478  
479  	err = nr_bhs = idx_clus = 0;
480  	count = FAT_START_ENT;
481  	fatent_init(&prev_ent);
482  	fatent_init(&fatent);
483  	fatent_set_entry(&fatent, sbi->prev_free + 1);
484  	while (count < sbi->max_cluster) {
485  		if (fatent.entry >= sbi->max_cluster)
486  			fatent.entry = FAT_START_ENT;
487  		fatent_set_entry(&fatent, fatent.entry);
488  		err = fat_ent_read_block(sb, &fatent);
489  		if (err)
490  			goto out;
491  
492  		/* Find the free entries in a block */
493  		do {
494  			if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
495  				int entry = fatent.entry;
496  
497  				/* make the cluster chain */
498  				ops->ent_put(&fatent, FAT_ENT_EOF);
499  				if (prev_ent.nr_bhs)
500  					ops->ent_put(&prev_ent, entry);
501  
502  				fat_collect_bhs(bhs, &nr_bhs, &fatent);
503  
504  				sbi->prev_free = entry;
505  				if (sbi->free_clusters != -1)
506  					sbi->free_clusters--;
507  
508  				cluster[idx_clus] = entry;
509  				idx_clus++;
510  				if (idx_clus == nr_cluster)
511  					goto out;
512  
513  				/*
514  				 * fat_collect_bhs() gets ref-count of bhs,
515  				 * so we can still use the prev_ent.
516  				 */
517  				prev_ent = fatent;
518  			}
519  			count++;
520  			if (count == sbi->max_cluster)
521  				break;
522  		} while (fat_ent_next(sbi, &fatent));
523  	}
524  
525  	/* Couldn't allocate the free entries */
526  	sbi->free_clusters = 0;
527  	sbi->free_clus_valid = 1;
528  	err = -ENOSPC;
529  
530  out:
531  	unlock_fat(sbi);
532  	mark_fsinfo_dirty(sb);
533  	fatent_brelse(&fatent);
534  	if (!err) {
535  		if (inode_needs_sync(inode))
536  			err = fat_sync_bhs(bhs, nr_bhs);
537  		if (!err)
538  			err = fat_mirror_bhs(sb, bhs, nr_bhs);
539  	}
540  	for (i = 0; i < nr_bhs; i++)
541  		brelse(bhs[i]);
542  
543  	if (err && idx_clus)
544  		fat_free_clusters(inode, cluster[0]);
545  
546  	return err;
547  }
548  
549  int fat_free_clusters(struct inode *inode, int cluster)
550  {
551  	struct super_block *sb = inode->i_sb;
552  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
553  	const struct fatent_operations *ops = sbi->fatent_ops;
554  	struct fat_entry fatent;
555  	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
556  	int i, err, nr_bhs;
557  	int first_cl = cluster, dirty_fsinfo = 0;
558  
559  	nr_bhs = 0;
560  	fatent_init(&fatent);
561  	lock_fat(sbi);
562  	do {
563  		cluster = fat_ent_read(inode, &fatent, cluster);
564  		if (cluster < 0) {
565  			err = cluster;
566  			goto error;
567  		} else if (cluster == FAT_ENT_FREE) {
568  			fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
569  				     __func__);
570  			err = -EIO;
571  			goto error;
572  		}
573  
574  		if (sbi->options.discard) {
575  			/*
576  			 * Issue discard for the sectors we no longer
577  			 * care about, batching contiguous clusters
578  			 * into one request
579  			 */
580  			if (cluster != fatent.entry + 1) {
581  				int nr_clus = fatent.entry - first_cl + 1;
582  
583  				sb_issue_discard(sb,
584  					fat_clus_to_blknr(sbi, first_cl),
585  					nr_clus * sbi->sec_per_clus,
586  					GFP_NOFS, 0);
587  
588  				first_cl = cluster;
589  			}
590  		}
591  
592  		ops->ent_put(&fatent, FAT_ENT_FREE);
593  		if (sbi->free_clusters != -1) {
594  			sbi->free_clusters++;
595  			dirty_fsinfo = 1;
596  		}
597  
598  		if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
599  			if (sb->s_flags & SB_SYNCHRONOUS) {
600  				err = fat_sync_bhs(bhs, nr_bhs);
601  				if (err)
602  					goto error;
603  			}
604  			err = fat_mirror_bhs(sb, bhs, nr_bhs);
605  			if (err)
606  				goto error;
607  			for (i = 0; i < nr_bhs; i++)
608  				brelse(bhs[i]);
609  			nr_bhs = 0;
610  		}
611  		fat_collect_bhs(bhs, &nr_bhs, &fatent);
612  	} while (cluster != FAT_ENT_EOF);
613  
614  	if (sb->s_flags & SB_SYNCHRONOUS) {
615  		err = fat_sync_bhs(bhs, nr_bhs);
616  		if (err)
617  			goto error;
618  	}
619  	err = fat_mirror_bhs(sb, bhs, nr_bhs);
620  error:
621  	fatent_brelse(&fatent);
622  	for (i = 0; i < nr_bhs; i++)
623  		brelse(bhs[i]);
624  	unlock_fat(sbi);
625  	if (dirty_fsinfo)
626  		mark_fsinfo_dirty(sb);
627  
628  	return err;
629  }
630  EXPORT_SYMBOL_GPL(fat_free_clusters);
631  
632  /* 128kb is the whole sectors for FAT12 and FAT16 */
633  #define FAT_READA_SIZE		(128 * 1024)
634  
635  static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
636  			  unsigned long reada_blocks)
637  {
638  	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
639  	sector_t blocknr;
640  	int i, offset;
641  
642  	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
643  
644  	for (i = 0; i < reada_blocks; i++)
645  		sb_breadahead(sb, blocknr + i);
646  }
647  
648  int fat_count_free_clusters(struct super_block *sb)
649  {
650  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
651  	const struct fatent_operations *ops = sbi->fatent_ops;
652  	struct fat_entry fatent;
653  	unsigned long reada_blocks, reada_mask, cur_block;
654  	int err = 0, free;
655  
656  	lock_fat(sbi);
657  	if (sbi->free_clusters != -1 && sbi->free_clus_valid)
658  		goto out;
659  
660  	reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
661  	reada_mask = reada_blocks - 1;
662  	cur_block = 0;
663  
664  	free = 0;
665  	fatent_init(&fatent);
666  	fatent_set_entry(&fatent, FAT_START_ENT);
667  	while (fatent.entry < sbi->max_cluster) {
668  		/* readahead of fat blocks */
669  		if ((cur_block & reada_mask) == 0) {
670  			unsigned long rest = sbi->fat_length - cur_block;
671  			fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
672  		}
673  		cur_block++;
674  
675  		err = fat_ent_read_block(sb, &fatent);
676  		if (err)
677  			goto out;
678  
679  		do {
680  			if (ops->ent_get(&fatent) == FAT_ENT_FREE)
681  				free++;
682  		} while (fat_ent_next(sbi, &fatent));
683  		cond_resched();
684  	}
685  	sbi->free_clusters = free;
686  	sbi->free_clus_valid = 1;
687  	mark_fsinfo_dirty(sb);
688  	fatent_brelse(&fatent);
689  out:
690  	unlock_fat(sbi);
691  	return err;
692  }
693  
694  static int fat_trim_clusters(struct super_block *sb, u32 clus, u32 nr_clus)
695  {
696  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
697  	return sb_issue_discard(sb, fat_clus_to_blknr(sbi, clus),
698  				nr_clus * sbi->sec_per_clus, GFP_NOFS, 0);
699  }
700  
701  int fat_trim_fs(struct inode *inode, struct fstrim_range *range)
702  {
703  	struct super_block *sb = inode->i_sb;
704  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
705  	const struct fatent_operations *ops = sbi->fatent_ops;
706  	struct fat_entry fatent;
707  	u64 ent_start, ent_end, minlen, trimmed = 0;
708  	u32 free = 0;
709  	unsigned long reada_blocks, reada_mask, cur_block = 0;
710  	int err = 0;
711  
712  	/*
713  	 * FAT data is organized as clusters, trim at the granulary of cluster.
714  	 *
715  	 * fstrim_range is in byte, convert vaules to cluster index.
716  	 * Treat sectors before data region as all used, not to trim them.
717  	 */
718  	ent_start = max_t(u64, range->start>>sbi->cluster_bits, FAT_START_ENT);
719  	ent_end = ent_start + (range->len >> sbi->cluster_bits) - 1;
720  	minlen = range->minlen >> sbi->cluster_bits;
721  
722  	if (ent_start >= sbi->max_cluster || range->len < sbi->cluster_size)
723  		return -EINVAL;
724  	if (ent_end >= sbi->max_cluster)
725  		ent_end = sbi->max_cluster - 1;
726  
727  	reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
728  	reada_mask = reada_blocks - 1;
729  
730  	fatent_init(&fatent);
731  	lock_fat(sbi);
732  	fatent_set_entry(&fatent, ent_start);
733  	while (fatent.entry <= ent_end) {
734  		/* readahead of fat blocks */
735  		if ((cur_block & reada_mask) == 0) {
736  			unsigned long rest = sbi->fat_length - cur_block;
737  			fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
738  		}
739  		cur_block++;
740  
741  		err = fat_ent_read_block(sb, &fatent);
742  		if (err)
743  			goto error;
744  		do {
745  			if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
746  				free++;
747  			} else if (free) {
748  				if (free >= minlen) {
749  					u32 clus = fatent.entry - free;
750  
751  					err = fat_trim_clusters(sb, clus, free);
752  					if (err && err != -EOPNOTSUPP)
753  						goto error;
754  					if (!err)
755  						trimmed += free;
756  					err = 0;
757  				}
758  				free = 0;
759  			}
760  		} while (fat_ent_next(sbi, &fatent) && fatent.entry <= ent_end);
761  
762  		if (fatal_signal_pending(current)) {
763  			err = -ERESTARTSYS;
764  			goto error;
765  		}
766  
767  		if (need_resched()) {
768  			fatent_brelse(&fatent);
769  			unlock_fat(sbi);
770  			cond_resched();
771  			lock_fat(sbi);
772  		}
773  	}
774  	/* handle scenario when tail entries are all free */
775  	if (free && free >= minlen) {
776  		u32 clus = fatent.entry - free;
777  
778  		err = fat_trim_clusters(sb, clus, free);
779  		if (err && err != -EOPNOTSUPP)
780  			goto error;
781  		if (!err)
782  			trimmed += free;
783  		err = 0;
784  	}
785  
786  error:
787  	fatent_brelse(&fatent);
788  	unlock_fat(sbi);
789  
790  	range->len = trimmed << sbi->cluster_bits;
791  
792  	return err;
793  }
794