[linux.git] / fs / fat / fatent.c

/*
 * Copyright (C) 2004, OGAWA Hirofumi
 * Released under GPL v2.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/msdos_fs.h>
#include <linux/blkdev.h>
#include "fat.h"

struct fatent_operations {
	void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
	void (*ent_set_ptr)(struct fat_entry *, int);
	int (*ent_bread)(struct super_block *, struct fat_entry *,
			 int, sector_t);
	int (*ent_get)(struct fat_entry *);
	void (*ent_put)(struct fat_entry *, int);
	int (*ent_next)(struct fat_entry *);
};

static DEFINE_SPINLOCK(fat12_entry_lock);

static void fat12_ent_blocknr(struct super_block *sb, int entry,
			      int *offset, sector_t *blocknr)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	int bytes = entry + (entry >> 1);
	WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
	*offset = bytes & (sb->s_blocksize - 1);
	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
}

static void fat_ent_blocknr(struct super_block *sb, int entry,
			    int *offset, sector_t *blocknr)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	int bytes = (entry << sbi->fatent_shift);
	WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
	*offset = bytes & (sb->s_blocksize - 1);
	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
}

static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
{
	struct buffer_head **bhs = fatent->bhs;
	if (fatent->nr_bhs == 1) {
		WARN_ON(offset >= (bhs[0]->b_size - 1));
		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
		fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
	} else {
		WARN_ON(offset != (bhs[0]->b_size - 1));
		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
		fatent->u.ent12_p[1] = bhs[1]->b_data;
	}
}

static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
{
	WARN_ON(offset & (2 - 1));
	fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
}

static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
{
	WARN_ON(offset & (4 - 1));
	fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
}

static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
			   int offset, sector_t blocknr)
{
	struct buffer_head **bhs = fatent->bhs;

	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
	bhs[0] = sb_bread(sb, blocknr);
	if (!bhs[0])
		goto err;

	if ((offset + 1) < sb->s_blocksize)
		fatent->nr_bhs = 1;
	else {
		/* This entry is block boundary, it needs the next block */
		blocknr++;
		bhs[1] = sb_bread(sb, blocknr);
		if (!bhs[1])
			goto err_brelse;
		fatent->nr_bhs = 2;
	}
	fat12_ent_set_ptr(fatent, offset);
	return 0;

err_brelse:
	brelse(bhs[0]);
err:
	printk(KERN_ERR "FAT: FAT read failed (blocknr %llu)\n", (llu)blocknr);
	return -EIO;
}

static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
			 int offset, sector_t blocknr)
{
	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;

	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
	fatent->bhs[0] = sb_bread(sb, blocknr);
	if (!fatent->bhs[0]) {
		printk(KERN_ERR "FAT: FAT read failed (blocknr %llu)\n",
		       (llu)blocknr);
		return -EIO;
	}
	fatent->nr_bhs = 1;
	ops->ent_set_ptr(fatent, offset);
	return 0;
}

static int fat12_ent_get(struct fat_entry *fatent)
{
	u8 **ent12_p = fatent->u.ent12_p;
	int next;

	spin_lock(&fat12_entry_lock);
	if (fatent->entry & 1)
		next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
	else
		next = (*ent12_p[1] << 8) | *ent12_p[0];
	spin_unlock(&fat12_entry_lock);

	next &= 0x0fff;
	if (next >= BAD_FAT12)
		next = FAT_ENT_EOF;
	return next;
}

static int fat16_ent_get(struct fat_entry *fatent)
{
	int next = le16_to_cpu(*fatent->u.ent16_p);
	WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
	if (next >= BAD_FAT16)
		next = FAT_ENT_EOF;
	return next;
}

static int fat32_ent_get(struct fat_entry *fatent)
{
	int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
	WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
	if (next >= BAD_FAT32)
		next = FAT_ENT_EOF;
	return next;
}

static void fat12_ent_put(struct fat_entry *fatent, int new)
{
	u8 **ent12_p = fatent->u.ent12_p;

	if (new == FAT_ENT_EOF)
		new = EOF_FAT12;

	spin_lock(&fat12_entry_lock);
	if (fatent->entry & 1) {
		*ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
		*ent12_p[1] = new >> 4;
	} else {
		*ent12_p[0] = new & 0xff;
		*ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
	}
	spin_unlock(&fat12_entry_lock);

	mark_buffer_dirty(fatent->bhs[0]);
	if (fatent->nr_bhs == 2)
		mark_buffer_dirty(fatent->bhs[1]);
}

static void fat16_ent_put(struct fat_entry *fatent, int new)
{
	if (new == FAT_ENT_EOF)
		new = EOF_FAT16;

	*fatent->u.ent16_p = cpu_to_le16(new);
	mark_buffer_dirty(fatent->bhs[0]);
}

static void fat32_ent_put(struct fat_entry *fatent, int new)
{
	if (new == FAT_ENT_EOF)
		new = EOF_FAT32;

	WARN_ON(new & 0xf0000000);
	new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
	*fatent->u.ent32_p = cpu_to_le32(new);
	mark_buffer_dirty(fatent->bhs[0]);
}

static int fat12_ent_next(struct fat_entry *fatent)
{
	u8 **ent12_p = fatent->u.ent12_p;
	struct buffer_head **bhs = fatent->bhs;
	u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);

	fatent->entry++;
	if (fatent->nr_bhs == 1) {
		WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 2)));
		WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1)));
		if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
			ent12_p[0] = nextp - 1;
			ent12_p[1] = nextp;
			return 1;
		}
	} else {
		WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1)));
		WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
		ent12_p[0] = nextp - 1;
		ent12_p[1] = nextp;
		brelse(bhs[0]);
		bhs[0] = bhs[1];
		fatent->nr_bhs = 1;
		return 1;
	}
	ent12_p[0] = NULL;
	ent12_p[1] = NULL;
	return 0;
}

static int fat16_ent_next(struct fat_entry *fatent)
{
	const struct buffer_head *bh = fatent->bhs[0];
	fatent->entry++;
	if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
		fatent->u.ent16_p++;
		return 1;
	}
	fatent->u.ent16_p = NULL;
	return 0;
}

static int fat32_ent_next(struct fat_entry *fatent)
{
	const struct buffer_head *bh = fatent->bhs[0];
	fatent->entry++;
	if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
		fatent->u.ent32_p++;
		return 1;
	}
	fatent->u.ent32_p = NULL;
	return 0;
}

static struct fatent_operations fat12_ops = {
	.ent_blocknr	= fat12_ent_blocknr,
	.ent_set_ptr	= fat12_ent_set_ptr,
	.ent_bread	= fat12_ent_bread,
	.ent_get	= fat12_ent_get,
	.ent_put	= fat12_ent_put,
	.ent_next	= fat12_ent_next,
};

static struct fatent_operations fat16_ops = {
	.ent_blocknr	= fat_ent_blocknr,
	.ent_set_ptr	= fat16_ent_set_ptr,
	.ent_bread	= fat_ent_bread,
	.ent_get	= fat16_ent_get,
	.ent_put	= fat16_ent_put,
	.ent_next	= fat16_ent_next,
};

static struct fatent_operations fat32_ops = {
	.ent_blocknr	= fat_ent_blocknr,
	.ent_set_ptr	= fat32_ent_set_ptr,
	.ent_bread	= fat_ent_bread,
	.ent_get	= fat32_ent_get,
	.ent_put	= fat32_ent_put,
	.ent_next	= fat32_ent_next,
};

static inline void lock_fat(struct msdos_sb_info *sbi)
{
	mutex_lock(&sbi->fat_lock);
}

static inline void unlock_fat(struct msdos_sb_info *sbi)
{
	mutex_unlock(&sbi->fat_lock);
}

void fat_ent_access_init(struct super_block *sb)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);

	mutex_init(&sbi->fat_lock);

	switch (sbi->fat_bits) {
	case 32:
		sbi->fatent_shift = 2;
		sbi->fatent_ops = &fat32_ops;
		break;
	case 16:
		sbi->fatent_shift = 1;
		sbi->fatent_ops = &fat16_ops;
		break;
	case 12:
		sbi->fatent_shift = -1;
		sbi->fatent_ops = &fat12_ops;
		break;
	}
}

static inline int fat_ent_update_ptr(struct super_block *sb,
				     struct fat_entry *fatent,
				     int offset, sector_t blocknr)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct fatent_operations *ops = sbi->fatent_ops;
	struct buffer_head **bhs = fatent->bhs;

	/* Is this fatent's blocks including this entry? */
	if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
		return 0;
	if (sbi->fat_bits == 12) {
		if ((offset + 1) < sb->s_blocksize) {
			/* This entry is on bhs[0]. */
			if (fatent->nr_bhs == 2) {
				brelse(bhs[1]);
				fatent->nr_bhs = 1;
			}
		} else {
			/* This entry needs the next block. */
			if (fatent->nr_bhs != 2)
				return 0;
			if (bhs[1]->b_blocknr != (blocknr + 1))
				return 0;
		}
	}
	ops->ent_set_ptr(fatent, offset);
	return 1;
}

int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
	struct fatent_operations *ops = sbi->fatent_ops;
	int err, offset;
	sector_t blocknr;

	if (entry < FAT_START_ENT || sbi->max_cluster <= entry) {
		fatent_brelse(fatent);
		fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", entry);
		return -EIO;
	}

	fatent_set_entry(fatent, entry);
	ops->ent_blocknr(sb, entry, &offset, &blocknr);

	if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
		fatent_brelse(fatent);
		err = ops->ent_bread(sb, fatent, offset, blocknr);
		if (err)
			return err;
	}
	return ops->ent_get(fatent);
}

/* FIXME: We can write the blocks as more big chunk. */
static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
			  int nr_bhs)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct buffer_head *c_bh;
	int err, n, copy;

	err = 0;
	for (copy = 1; copy < sbi->fats; copy++) {
		sector_t backup_fat = sbi->fat_length * copy;

		for (n = 0; n < nr_bhs; n++) {
			c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
			if (!c_bh) {
				err = -ENOMEM;
				goto error;
			}
			memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
			set_buffer_uptodate(c_bh);
			mark_buffer_dirty(c_bh);
			if (sb->s_flags & MS_SYNCHRONOUS)
				err = sync_dirty_buffer(c_bh);
			brelse(c_bh);
			if (err)
				goto error;
		}
	}
error:
	return err;
}

int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
		  int new, int wait)
{
	struct super_block *sb = inode->i_sb;
	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
	int err;

	ops->ent_put(fatent, new);
	if (wait) {
		err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
		if (err)
			return err;
	}
	return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
}

static inline int fat_ent_next(struct msdos_sb_info *sbi,
			       struct fat_entry *fatent)
{
	if (sbi->fatent_ops->ent_next(fatent)) {
		if (fatent->entry < sbi->max_cluster)
			return 1;
	}
	return 0;
}

static inline int fat_ent_read_block(struct super_block *sb,
				     struct fat_entry *fatent)
{
	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
	sector_t blocknr;
	int offset;

	fatent_brelse(fatent);
	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
	return ops->ent_bread(sb, fatent, offset, blocknr);
}

static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
			    struct fat_entry *fatent)
{
	int n, i;

	for (n = 0; n < fatent->nr_bhs; n++) {
		for (i = 0; i < *nr_bhs; i++) {
			if (fatent->bhs[n] == bhs[i])
				break;
		}
		if (i == *nr_bhs) {
			get_bh(fatent->bhs[n]);
			bhs[i] = fatent->bhs[n];
			(*nr_bhs)++;
		}
	}
}

int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct fatent_operations *ops = sbi->fatent_ops;
	struct fat_entry fatent, prev_ent;
	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	int i, count, err, nr_bhs, idx_clus;

	BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));	/* fixed limit */

	lock_fat(sbi);
	if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
	    sbi->free_clusters < nr_cluster) {
		unlock_fat(sbi);
		return -ENOSPC;
	}

	err = nr_bhs = idx_clus = 0;
	count = FAT_START_ENT;
	fatent_init(&prev_ent);
	fatent_init(&fatent);
	fatent_set_entry(&fatent, sbi->prev_free + 1);
	while (count < sbi->max_cluster) {
		if (fatent.entry >= sbi->max_cluster)
			fatent.entry = FAT_START_ENT;
		fatent_set_entry(&fatent, fatent.entry);
		err = fat_ent_read_block(sb, &fatent);
		if (err)
			goto out;

		/* Find the free entries in a block */
		do {
			if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
				int entry = fatent.entry;

				/* make the cluster chain */
				ops->ent_put(&fatent, FAT_ENT_EOF);
				if (prev_ent.nr_bhs)
					ops->ent_put(&prev_ent, entry);

				fat_collect_bhs(bhs, &nr_bhs, &fatent);

				sbi->prev_free = entry;
				if (sbi->free_clusters != -1)
					sbi->free_clusters--;
				sb->s_dirt = 1;

				cluster[idx_clus] = entry;
				idx_clus++;
				if (idx_clus == nr_cluster)
					goto out;

				/*
				 * fat_collect_bhs() gets ref-count of bhs,
				 * so we can still use the prev_ent.
				 */
				prev_ent = fatent;
			}
			count++;
			if (count == sbi->max_cluster)
				break;
		} while (fat_ent_next(sbi, &fatent));
	}

	/* Couldn't allocate the free entries */
	sbi->free_clusters = 0;
	sbi->free_clus_valid = 1;
	sb->s_dirt = 1;
	err = -ENOSPC;

out:
	unlock_fat(sbi);
	fatent_brelse(&fatent);
	if (!err) {
		if (inode_needs_sync(inode))
			err = fat_sync_bhs(bhs, nr_bhs);
		if (!err)
			err = fat_mirror_bhs(sb, bhs, nr_bhs);
	}
	for (i = 0; i < nr_bhs; i++)
		brelse(bhs[i]);

	if (err && idx_clus)
		fat_free_clusters(inode, cluster[0]);

	return err;
}

int fat_free_clusters(struct inode *inode, int cluster)
{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct fatent_operations *ops = sbi->fatent_ops;
	struct fat_entry fatent;
	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	int i, err, nr_bhs;
	int first_cl = cluster;

	nr_bhs = 0;
	fatent_init(&fatent);
	lock_fat(sbi);
	do {
		cluster = fat_ent_read(inode, &fatent, cluster);
		if (cluster < 0) {
			err = cluster;
			goto error;
		} else if (cluster == FAT_ENT_FREE) {
			fat_fs_panic(sb, "%s: deleting FAT entry beyond EOF",
				     __func__);
			err = -EIO;
			goto error;
		}

		/* 
		 * Issue discard for the sectors we no longer care about,
		 * batching contiguous clusters into one request
		 */
		if (cluster != fatent.entry + 1) {
			int nr_clus = fatent.entry - first_cl + 1;

			sb_issue_discard(sb, fat_clus_to_blknr(sbi, first_cl),
					 nr_clus * sbi->sec_per_clus);
			first_cl = cluster;
		}

		ops->ent_put(&fatent, FAT_ENT_FREE);
		if (sbi->free_clusters != -1) {
			sbi->free_clusters++;
			sb->s_dirt = 1;
		}

		if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
			if (sb->s_flags & MS_SYNCHRONOUS) {
				err = fat_sync_bhs(bhs, nr_bhs);
				if (err)
					goto error;
			}
			err = fat_mirror_bhs(sb, bhs, nr_bhs);
			if (err)
				goto error;
			for (i = 0; i < nr_bhs; i++)
				brelse(bhs[i]);
			nr_bhs = 0;
		}
		fat_collect_bhs(bhs, &nr_bhs, &fatent);
	} while (cluster != FAT_ENT_EOF);

	if (sb->s_flags & MS_SYNCHRONOUS) {
		err = fat_sync_bhs(bhs, nr_bhs);
		if (err)
			goto error;
	}
	err = fat_mirror_bhs(sb, bhs, nr_bhs);
error:
	fatent_brelse(&fatent);
	for (i = 0; i < nr_bhs; i++)
		brelse(bhs[i]);
	unlock_fat(sbi);

	return err;
}

EXPORT_SYMBOL_GPL(fat_free_clusters);

/* 128kb is the whole sectors for FAT12 and FAT16 */
#define FAT_READA_SIZE		(128 * 1024)

static void fat_ent_reada(struct super_block *sb, struct fat_entry *fatent,
			  unsigned long reada_blocks)
{
	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
	sector_t blocknr;
	int i, offset;

	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);

	for (i = 0; i < reada_blocks; i++)
		sb_breadahead(sb, blocknr + i);
}

int fat_count_free_clusters(struct super_block *sb)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct fatent_operations *ops = sbi->fatent_ops;
	struct fat_entry fatent;
	unsigned long reada_blocks, reada_mask, cur_block;
	int err = 0, free;

	lock_fat(sbi);
	if (sbi->free_clusters != -1 && sbi->free_clus_valid)
		goto out;

	reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
	reada_mask = reada_blocks - 1;
	cur_block = 0;

	free = 0;
	fatent_init(&fatent);
	fatent_set_entry(&fatent, FAT_START_ENT);
	while (fatent.entry < sbi->max_cluster) {
		/* readahead of fat blocks */
		if ((cur_block & reada_mask) == 0) {
			unsigned long rest = sbi->fat_length - cur_block;
			fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
		}
		cur_block++;

		err = fat_ent_read_block(sb, &fatent);
		if (err)
			goto out;

		do {
			if (ops->ent_get(&fatent) == FAT_ENT_FREE)
				free++;
		} while (fat_ent_next(sbi, &fatent));
	}
	sbi->free_clusters = free;
	sbi->free_clus_valid = 1;
	sb->s_dirt = 1;
	fatent_brelse(&fatent);
out:
	unlock_fat(sbi);
	return err;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Copyright (C) 2004, OGAWA Hirofumi
	3	* Released under GPL v2.
	4	*/
	5
	6	#include <linux/module.h>
	7	#include <linux/fs.h>
	8	#include <linux/msdos_fs.h>
8c540a96	9	#include <linux/blkdev.h>
9e975dae	10	#include "fat.h"
1da177e4 LT	11
	12	struct fatent_operations {
	13	void (ent_blocknr)(struct super_block , int, int , sector_t );
	14	void (ent_set_ptr)(struct fat_entry , int);
	15	int (ent_bread)(struct super_block , struct fat_entry *,
	16	int, sector_t);
	17	int (ent_get)(struct fat_entry );
	18	void (ent_put)(struct fat_entry , int);
	19	int (ent_next)(struct fat_entry );
	20	};
	21
98283bb4 OH	22	static DEFINE_SPINLOCK(fat12_entry_lock);
98283bb4 OH	23
1da177e4 LT	24	static void fat12_ent_blocknr(struct super_block *sb, int entry,
	25	int offset, sector_t blocknr)
	26	{
	27	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	28	int bytes = entry + (entry >> 1);
	29	WARN_ON(entry < FAT_START_ENT \|\| sbi->max_cluster <= entry);
	30	*offset = bytes & (sb->s_blocksize - 1);
	31	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
	32	}
	33
	34	static void fat_ent_blocknr(struct super_block *sb, int entry,
	35	int offset, sector_t blocknr)
	36	{
	37	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	38	int bytes = (entry << sbi->fatent_shift);
	39	WARN_ON(entry < FAT_START_ENT \|\| sbi->max_cluster <= entry);
	40	*offset = bytes & (sb->s_blocksize - 1);
	41	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
	42	}
	43
	44	static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
	45	{
	46	struct buffer_head **bhs = fatent->bhs;
	47	if (fatent->nr_bhs == 1) {
	48	WARN_ON(offset >= (bhs[0]->b_size - 1));
	49	fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
	50	fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
	51	} else {
	52	WARN_ON(offset != (bhs[0]->b_size - 1));
	53	fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
	54	fatent->u.ent12_p[1] = bhs[1]->b_data;
	55	}
	56	}
	57
	58	static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
	59	{
	60	WARN_ON(offset & (2 - 1));
	61	fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
	62	}
	63
	64	static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
	65	{
	66	WARN_ON(offset & (4 - 1));
	67	fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
	68	}
	69
	70	static int fat12_ent_bread(struct super_block sb, struct fat_entry fatent,
	71	int offset, sector_t blocknr)
	72	{
	73	struct buffer_head **bhs = fatent->bhs;
	74
	75	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
	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:
c3302931	96	printk(KERN_ERR "FAT: FAT read failed (blocknr %llu)\n", (llu)blocknr);
1da177e4 LT	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	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
	104
	105	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
	106	fatent->bhs[0] = sb_bread(sb, blocknr);
	107	if (!fatent->bhs[0]) {
	108	printk(KERN_ERR "FAT: FAT read failed (blocknr %llu)\n",
c3302931	109	(llu)blocknr);
1da177e4 LT	110	return -EIO;
	111	}
	112	fatent->nr_bhs = 1;
	113	ops->ent_set_ptr(fatent, offset);
	114	return 0;
	115	}
	116
	117	static int fat12_ent_get(struct fat_entry *fatent)
	118	{
	119	u8 **ent12_p = fatent->u.ent12_p;
	120	int next;
	121
98283bb4	122	spin_lock(&fat12_entry_lock);
1da177e4 LT	123	if (fatent->entry & 1)
	124	next = (ent12_p[0] >> 4) \| (ent12_p[1] << 4);
	125	else
	126	next = (ent12_p[1] << 8) \| ent12_p[0];
98283bb4 OH	127	spin_unlock(&fat12_entry_lock);
98283bb4 OH	128
1da177e4 LT	129	next &= 0x0fff;
	130	if (next >= BAD_FAT12)
	131	next = FAT_ENT_EOF;
	132	return next;
	133	}
	134
	135	static int fat16_ent_get(struct fat_entry *fatent)
	136	{
	137	int next = le16_to_cpu(*fatent->u.ent16_p);
	138	WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
	139	if (next >= BAD_FAT16)
	140	next = FAT_ENT_EOF;
	141	return next;
	142	}
	143
	144	static int fat32_ent_get(struct fat_entry *fatent)
	145	{
	146	int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
	147	WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
	148	if (next >= BAD_FAT32)
	149	next = FAT_ENT_EOF;
	150	return next;
	151	}
	152
	153	static void fat12_ent_put(struct fat_entry *fatent, int new)
	154	{
	155	u8 **ent12_p = fatent->u.ent12_p;
	156
	157	if (new == FAT_ENT_EOF)
	158	new = EOF_FAT12;
	159
98283bb4	160	spin_lock(&fat12_entry_lock);
1da177e4 LT	161	if (fatent->entry & 1) {
	162	ent12_p[0] = (new << 4) \| (ent12_p[0] & 0x0f);
	163	*ent12_p[1] = new >> 4;
	164	} else {
	165	*ent12_p[0] = new & 0xff;
	166	ent12_p[1] = (ent12_p[1] & 0xf0) \| (new >> 8);
	167	}
98283bb4	168	spin_unlock(&fat12_entry_lock);
1da177e4 LT	169
	170	mark_buffer_dirty(fatent->bhs[0]);
	171	if (fatent->nr_bhs == 2)
	172	mark_buffer_dirty(fatent->bhs[1]);
	173	}
	174
	175	static void fat16_ent_put(struct fat_entry *fatent, int new)
	176	{
	177	if (new == FAT_ENT_EOF)
	178	new = EOF_FAT16;
	179
	180	*fatent->u.ent16_p = cpu_to_le16(new);
	181	mark_buffer_dirty(fatent->bhs[0]);
	182	}
	183
	184	static void fat32_ent_put(struct fat_entry *fatent, int new)
	185	{
	186	if (new == FAT_ENT_EOF)
	187	new = EOF_FAT32;
	188
	189	WARN_ON(new & 0xf0000000);
	190	new \|= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
	191	*fatent->u.ent32_p = cpu_to_le32(new);
	192	mark_buffer_dirty(fatent->bhs[0]);
	193	}
	194
	195	static int fat12_ent_next(struct fat_entry *fatent)
	196	{
	197	u8 **ent12_p = fatent->u.ent12_p;
	198	struct buffer_head **bhs = fatent->bhs;
	199	u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
	200
	201	fatent->entry++;
	202	if (fatent->nr_bhs == 1) {
	203	WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 2)));
	204	WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data + (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 + (bhs[0]->b_size - 1)));
	212	WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
	213	ent12_p[0] = nextp - 1;
	214	ent12_p[1] = nextp;
	215	brelse(bhs[0]);
	216	bhs[0] = bhs[1];
	217	fatent->nr_bhs = 1;
	218	return 1;
	219	}
	220	ent12_p[0] = NULL;
	221	ent12_p[1] = NULL;
	222	return 0;
	223	}
	224
	225	static int fat16_ent_next(struct fat_entry *fatent)
	226	{
	227	const struct buffer_head *bh = fatent->bhs[0];
	228	fatent->entry++;
	229	if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
	230	fatent->u.ent16_p++;
	231	return 1;
	232	}
233	fatent->u.ent16_p = NULL;
234	return 0;
235	}
236
237	static int fat32_ent_next(struct fat_entry *fatent)
238	{
239	const struct buffer_head *bh = fatent->bhs[0];
240	fatent->entry++;
241	if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
242	fatent->u.ent32_p++;
243	return 1;
244	}
245	fatent->u.ent32_p = NULL;
246	return 0;
247	}
248
249	static struct fatent_operations fat12_ops = {
250	.ent_blocknr = fat12_ent_blocknr,
251	.ent_set_ptr = fat12_ent_set_ptr,
252	.ent_bread = fat12_ent_bread,
253	.ent_get = fat12_ent_get,
254	.ent_put = fat12_ent_put,
255	.ent_next = fat12_ent_next,
256	};
257
258	static struct fatent_operations fat16_ops = {
259	.ent_blocknr = fat_ent_blocknr,
260	.ent_set_ptr = fat16_ent_set_ptr,
261	.ent_bread = fat_ent_bread,
262	.ent_get = fat16_ent_get,
263	.ent_put = fat16_ent_put,
264	.ent_next = fat16_ent_next,
265	};
266
267	static struct fatent_operations fat32_ops = {
268	.ent_blocknr = fat_ent_blocknr,
269	.ent_set_ptr = fat32_ent_set_ptr,
270	.ent_bread = fat_ent_bread,
271	.ent_get = fat32_ent_get,
272	.ent_put = fat32_ent_put,
273	.ent_next = fat32_ent_next,
274	};
275
276	static inline void lock_fat(struct msdos_sb_info *sbi)
277	{
6b9438e1	278	mutex_lock(&sbi->fat_lock);
1da177e4 LT	279	}
	280
	281	static inline void unlock_fat(struct msdos_sb_info *sbi)
	282	{
6b9438e1	283	mutex_unlock(&sbi->fat_lock);
1da177e4 LT	284	}
	285
	286	void fat_ent_access_init(struct super_block *sb)
	287	{
	288	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	289
6b9438e1	290	mutex_init(&sbi->fat_lock);
1da177e4 LT	291
	292	switch (sbi->fat_bits) {
	293	case 32:
	294	sbi->fatent_shift = 2;
	295	sbi->fatent_ops = &fat32_ops;
	296	break;
	297	case 16:
	298	sbi->fatent_shift = 1;
	299	sbi->fatent_ops = &fat16_ops;
	300	break;
	301	case 12:
	302	sbi->fatent_shift = -1;
	303	sbi->fatent_ops = &fat12_ops;
	304	break;
	305	}
	306	}
	307
	308	static inline int fat_ent_update_ptr(struct super_block *sb,
	309	struct fat_entry *fatent,
	310	int offset, sector_t blocknr)
	311	{
	312	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	313	struct fatent_operations *ops = sbi->fatent_ops;
	314	struct buffer_head **bhs = fatent->bhs;
	315
	316	/* Is this fatent's blocks including this entry? */
	317	if (!fatent->nr_bhs \|\| bhs[0]->b_blocknr != blocknr)
	318	return 0;
5e35dd46 OH	319	if (sbi->fat_bits == 12) {
	320	if ((offset + 1) < sb->s_blocksize) {
	321	/* This entry is on bhs[0]. */
	322	if (fatent->nr_bhs == 2) {
	323	brelse(bhs[1]);
	324	fatent->nr_bhs = 1;
	325	}
	326	} else {
	327	/* This entry needs the next block. */
	328	if (fatent->nr_bhs != 2)
	329	return 0;
	330	if (bhs[1]->b_blocknr != (blocknr + 1))
	331	return 0;
	332	}
1da177e4 LT	333	}
	334	ops->ent_set_ptr(fatent, offset);
	335	return 1;
	336	}
	337
	338	int fat_ent_read(struct inode inode, struct fat_entry fatent, int entry)
	339	{
	340	struct super_block *sb = inode->i_sb;
	341	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
	342	struct fatent_operations *ops = sbi->fatent_ops;
	343	int err, offset;
	344	sector_t blocknr;
	345
	346	if (entry < FAT_START_ENT \|\| sbi->max_cluster <= entry) {
	347	fatent_brelse(fatent);
	348	fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", entry);
	349	return -EIO;
	350	}
	351
	352	fatent_set_entry(fatent, entry);
	353	ops->ent_blocknr(sb, entry, &offset, &blocknr);
	354
	355	if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
	356	fatent_brelse(fatent);
	357	err = ops->ent_bread(sb, fatent, offset, blocknr);
	358	if (err)
	359	return err;
	360	}
	361	return ops->ent_get(fatent);
	362	}
	363
	364	/* FIXME: We can write the blocks as more big chunk. */
	365	static int fat_mirror_bhs(struct super_block sb, struct buffer_head *bhs,
	366	int nr_bhs)
	367	{
	368	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	369	struct buffer_head *c_bh;
	370	int err, n, copy;
	371
	372	err = 0;
	373	for (copy = 1; copy < sbi->fats; copy++) {
	374	sector_t backup_fat = sbi->fat_length * copy;
	375
	376	for (n = 0; n < nr_bhs; n++) {
	377	c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
	378	if (!c_bh) {
	379	err = -ENOMEM;
	380	goto error;
	381	}
	382	memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
	383	set_buffer_uptodate(c_bh);
	384	mark_buffer_dirty(c_bh);
	385	if (sb->s_flags & MS_SYNCHRONOUS)
	386	err = sync_dirty_buffer(c_bh);
	387	brelse(c_bh);
	388	if (err)
	389	goto error;
	390	}
	391	}
	392	error:
	393	return err;
	394	}
	395
	396	int fat_ent_write(struct inode inode, struct fat_entry fatent,
397	int new, int wait)
398	{
399	struct super_block *sb = inode->i_sb;
400	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
401	int err;
402
403	ops->ent_put(fatent, new);
404	if (wait) {
405	err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
406	if (err)
407	return err;
408	}
409	return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
410	}
411
412	static inline int fat_ent_next(struct msdos_sb_info *sbi,
413	struct fat_entry *fatent)
414	{
415	if (sbi->fatent_ops->ent_next(fatent)) {
416	if (fatent->entry < sbi->max_cluster)
417	return 1;
418	}
419	return 0;
420	}
421
422	static inline int fat_ent_read_block(struct super_block *sb,
423	struct fat_entry *fatent)
424	{
425	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
426	sector_t blocknr;
427	int offset;
428
429	fatent_brelse(fatent);
430	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
431	return ops->ent_bread(sb, fatent, offset, blocknr);
432	}
433
434	static void fat_collect_bhs(struct buffer_head *bhs, int nr_bhs,
435	struct fat_entry *fatent)
436	{
437	int n, i;
438
439	for (n = 0; n < fatent->nr_bhs; n++) {
440	for (i = 0; i < *nr_bhs; i++) {
441	if (fatent->bhs[n] == bhs[i])
442	break;
443	}
444	if (i == *nr_bhs) {
445	get_bh(fatent->bhs[n]);
446	bhs[i] = fatent->bhs[n];
447	(*nr_bhs)++;
448	}
449	}
450	}
451
452	int fat_alloc_clusters(struct inode inode, int cluster, int nr_cluster)
453	{
454	struct super_block *sb = inode->i_sb;
455	struct msdos_sb_info *sbi = MSDOS_SB(sb);
456	struct fatent_operations *ops = sbi->fatent_ops;
457	struct fat_entry fatent, prev_ent;
458	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
459	int i, count, err, nr_bhs, idx_clus;
460
461	BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2)); /* fixed limit */
462
463	lock_fat(sbi);
606e423e OH	464	if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
606e423e OH	465	sbi->free_clusters < nr_cluster) {
1da177e4 LT	466	unlock_fat(sbi);
	467	return -ENOSPC;
	468	}
	469
	470	err = nr_bhs = idx_clus = 0;
	471	count = FAT_START_ENT;
	472	fatent_init(&prev_ent);
	473	fatent_init(&fatent);
	474	fatent_set_entry(&fatent, sbi->prev_free + 1);
	475	while (count < sbi->max_cluster) {
	476	if (fatent.entry >= sbi->max_cluster)
	477	fatent.entry = FAT_START_ENT;
	478	fatent_set_entry(&fatent, fatent.entry);
	479	err = fat_ent_read_block(sb, &fatent);
	480	if (err)
	481	goto out;
	482
	483	/* Find the free entries in a block */
	484	do {
	485	if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
	486	int entry = fatent.entry;
	487
	488	/* make the cluster chain */
	489	ops->ent_put(&fatent, FAT_ENT_EOF);
	490	if (prev_ent.nr_bhs)
	491	ops->ent_put(&prev_ent, entry);
	492
	493	fat_collect_bhs(bhs, &nr_bhs, &fatent);
	494
	495	sbi->prev_free = entry;
	496	if (sbi->free_clusters != -1)
	497	sbi->free_clusters--;
a6bf6b21	498	sb->s_dirt = 1;
1da177e4 LT	499
	500	cluster[idx_clus] = entry;
	501	idx_clus++;
	502	if (idx_clus == nr_cluster)
	503	goto out;
	504
	505	/*
	506	* fat_collect_bhs() gets ref-count of bhs,
	507	* so we can still use the prev_ent.
	508	*/
	509	prev_ent = fatent;
	510	}
	511	count++;
	512	if (count == sbi->max_cluster)
	513	break;
	514	} while (fat_ent_next(sbi, &fatent));
	515	}
	516
	517	/* Couldn't allocate the free entries */
	518	sbi->free_clusters = 0;
606e423e	519	sbi->free_clus_valid = 1;
a6bf6b21	520	sb->s_dirt = 1;
1da177e4 LT	521	err = -ENOSPC;
	522
	523	out:
	524	unlock_fat(sbi);
	525	fatent_brelse(&fatent);
	526	if (!err) {
	527	if (inode_needs_sync(inode))
	528	err = fat_sync_bhs(bhs, nr_bhs);
	529	if (!err)
	530	err = fat_mirror_bhs(sb, bhs, nr_bhs);
	531	}
	532	for (i = 0; i < nr_bhs; i++)
	533	brelse(bhs[i]);
1da177e4 LT	534
	535	if (err && idx_clus)
	536	fat_free_clusters(inode, cluster[0]);
	537
	538	return err;
	539	}
	540
	541	int fat_free_clusters(struct inode *inode, int cluster)
	542	{
	543	struct super_block *sb = inode->i_sb;
	544	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	545	struct fatent_operations *ops = sbi->fatent_ops;
	546	struct fat_entry fatent;
	547	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	548	int i, err, nr_bhs;
8c540a96	549	int first_cl = cluster;
1da177e4 LT	550
	551	nr_bhs = 0;
	552	fatent_init(&fatent);
	553	lock_fat(sbi);
	554	do {
	555	cluster = fat_ent_read(inode, &fatent, cluster);
	556	if (cluster < 0) {
	557	err = cluster;
	558	goto error;
	559	} else if (cluster == FAT_ENT_FREE) {
	560	fat_fs_panic(sb, "%s: deleting FAT entry beyond EOF",
8e24eea7	561	__func__);
1da177e4 LT	562	err = -EIO;
	563	goto error;
	564	}
	565
8c540a96 DW	566	/*
	567	* Issue discard for the sectors we no longer care about,
	568	* batching contiguous clusters into one request
	569	*/
	570	if (cluster != fatent.entry + 1) {
	571	int nr_clus = fatent.entry - first_cl + 1;
	572
	573	sb_issue_discard(sb, fat_clus_to_blknr(sbi, first_cl),
	574	nr_clus * sbi->sec_per_clus);
	575	first_cl = cluster;
	576	}
	577
1da177e4	578	ops->ent_put(&fatent, FAT_ENT_FREE);
a6bf6b21	579	if (sbi->free_clusters != -1) {
1da177e4	580	sbi->free_clusters++;
a6bf6b21 OH	581	sb->s_dirt = 1;
a6bf6b21 OH	582	}
1da177e4 LT	583
	584	if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
	585	if (sb->s_flags & MS_SYNCHRONOUS) {
	586	err = fat_sync_bhs(bhs, nr_bhs);
	587	if (err)
	588	goto error;
	589	}
	590	err = fat_mirror_bhs(sb, bhs, nr_bhs);
	591	if (err)
	592	goto error;
	593	for (i = 0; i < nr_bhs; i++)
	594	brelse(bhs[i]);
	595	nr_bhs = 0;
	596	}
	597	fat_collect_bhs(bhs, &nr_bhs, &fatent);
	598	} while (cluster != FAT_ENT_EOF);
	599
	600	if (sb->s_flags & MS_SYNCHRONOUS) {
	601	err = fat_sync_bhs(bhs, nr_bhs);
	602	if (err)
	603	goto error;
	604	}
	605	err = fat_mirror_bhs(sb, bhs, nr_bhs);
	606	error:
	607	fatent_brelse(&fatent);
	608	for (i = 0; i < nr_bhs; i++)
	609	brelse(bhs[i]);
	610	unlock_fat(sbi);
	611
1da177e4 LT	612	return err;
	613	}
	614
7c709d00	615	EXPORT_SYMBOL_GPL(fat_free_clusters);
1da177e4	616
9f966be8 OH	617	/* 128kb is the whole sectors for FAT12 and FAT16 */
	618	#define FAT_READA_SIZE (128 * 1024)
	619
	620	static void fat_ent_reada(struct super_block sb, struct fat_entry fatent,
	621	unsigned long reada_blocks)
	622	{
	623	struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
	624	sector_t blocknr;
	625	int i, offset;
	626
	627	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
	628
	629	for (i = 0; i < reada_blocks; i++)
	630	sb_breadahead(sb, blocknr + i);
	631	}
	632
1da177e4 LT	633	int fat_count_free_clusters(struct super_block *sb)
	634	{
	635	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	636	struct fatent_operations *ops = sbi->fatent_ops;
	637	struct fat_entry fatent;
9f966be8	638	unsigned long reada_blocks, reada_mask, cur_block;
1da177e4 LT	639	int err = 0, free;
	640
	641	lock_fat(sbi);
606e423e	642	if (sbi->free_clusters != -1 && sbi->free_clus_valid)
1da177e4 LT	643	goto out;
1da177e4 LT	644
9f966be8 OH	645	reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
	646	reada_mask = reada_blocks - 1;
	647	cur_block = 0;
	648
1da177e4 LT	649	free = 0;
	650	fatent_init(&fatent);
	651	fatent_set_entry(&fatent, FAT_START_ENT);
	652	while (fatent.entry < sbi->max_cluster) {
9f966be8 OH	653	/* readahead of fat blocks */
	654	if ((cur_block & reada_mask) == 0) {
	655	unsigned long rest = sbi->fat_length - cur_block;
	656	fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
	657	}
	658	cur_block++;
	659
1da177e4 LT	660	err = fat_ent_read_block(sb, &fatent);
	661	if (err)
	662	goto out;
	663
	664	do {
	665	if (ops->ent_get(&fatent) == FAT_ENT_FREE)
	666	free++;
	667	} while (fat_ent_next(sbi, &fatent));
	668	}
	669	sbi->free_clusters = free;
606e423e	670	sbi->free_clus_valid = 1;
a6bf6b21	671	sb->s_dirt = 1;
1da177e4 LT	672	fatent_brelse(&fatent);
	673	out:
	674	unlock_fat(sbi);
	675	return err;
	676	}