[mirror_ubuntu-artful-kernel.git] / fs / fat / fatent.c

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

#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);
	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;

	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:
	fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
	return -EIO;
}

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

	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
	fatent->bhs[0] = sb_bread(sb, blocknr);
	if (!fatent->bhs[0]) {
		fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
		       (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_inode(fatent->bhs[0], fatent->fat_inode);
	if (fatent->nr_bhs == 2)
		mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
}

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_inode(fatent->bhs[0], fatent->fat_inode);
}

static void fat32_ent_put(struct fat_entry *fatent, int new)
{
	WARN_ON(new & 0xf0000000);
	new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
	*fatent->u.ent32_p = cpu_to_le32(new);
	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
}

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

	if (sb->s_flags & MS_RDONLY || sbi->fat_bits != 32)
		return;

	__mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
}

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);
	const 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);
	const 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_error(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_inode(c_bh, sbi->fat_inode);
			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;
	const 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)
{
	const 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);
	const 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--;

				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;
	err = -ENOSPC;

out:
	unlock_fat(sbi);
	mark_fsinfo_dirty(sb);
	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);
	const 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, dirty_fsinfo = 0;

	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_error(sb, "%s: deleting FAT entry beyond EOF",
				     __func__);
			err = -EIO;
			goto error;
		}

		if (sbi->options.discard) {
			/*
			 * 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,
					GFP_NOFS, 0);

				first_cl = cluster;
			}
		}

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

	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)
{
	const 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);
	const 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;
	mark_fsinfo_dirty(sb);
	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
8c540a96	6	#include <linux/blkdev.h>
9e975dae	7	#include "fat.h"
1da177e4 LT	8
	9	struct fatent_operations {
	10	void (ent_blocknr)(struct super_block , int, int , sector_t );
	11	void (ent_set_ptr)(struct fat_entry , int);
	12	int (ent_bread)(struct super_block , struct fat_entry *,
	13	int, sector_t);
	14	int (ent_get)(struct fat_entry );
	15	void (ent_put)(struct fat_entry , int);
	16	int (ent_next)(struct fat_entry );
	17	};
	18
98283bb4 OH	19	static DEFINE_SPINLOCK(fat12_entry_lock);
98283bb4 OH	20
1da177e4 LT	21	static void fat12_ent_blocknr(struct super_block *sb, int entry,
	22	int offset, sector_t blocknr)
	23	{
	24	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	25	int bytes = entry + (entry >> 1);
	26	WARN_ON(entry < FAT_START_ENT \|\| sbi->max_cluster <= entry);
	27	*offset = bytes & (sb->s_blocksize - 1);
	28	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
	29	}
	30
	31	static void fat_ent_blocknr(struct super_block *sb, int entry,
	32	int offset, sector_t blocknr)
	33	{
	34	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	35	int bytes = (entry << sbi->fatent_shift);
	36	WARN_ON(entry < FAT_START_ENT \|\| sbi->max_cluster <= entry);
	37	*offset = bytes & (sb->s_blocksize - 1);
	38	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
	39	}
	40
	41	static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
	42	{
	43	struct buffer_head **bhs = fatent->bhs;
	44	if (fatent->nr_bhs == 1) {
	45	WARN_ON(offset >= (bhs[0]->b_size - 1));
	46	fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
	47	fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
	48	} else {
	49	WARN_ON(offset != (bhs[0]->b_size - 1));
	50	fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
	51	fatent->u.ent12_p[1] = bhs[1]->b_data;
	52	}
	53	}
	54
	55	static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
	56	{
	57	WARN_ON(offset & (2 - 1));
	58	fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
	59	}
	60
	61	static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
	62	{
	63	WARN_ON(offset & (4 - 1));
	64	fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
	65	}
	66
	67	static int fat12_ent_bread(struct super_block sb, struct fat_entry fatent,
	68	int offset, sector_t blocknr)
	69	{
	70	struct buffer_head **bhs = fatent->bhs;
	71
	72	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
b522412a AV	73	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
b522412a AV	74
1da177e4 LT	75	bhs[0] = sb_bread(sb, blocknr);
	76	if (!bhs[0])
	77	goto err;
	78
	79	if ((offset + 1) < sb->s_blocksize)
	80	fatent->nr_bhs = 1;
	81	else {
	82	/* This entry is block boundary, it needs the next block */
	83	blocknr++;
	84	bhs[1] = sb_bread(sb, blocknr);
	85	if (!bhs[1])
	86	goto err_brelse;
	87	fatent->nr_bhs = 2;
	88	}
	89	fat12_ent_set_ptr(fatent, offset);
	90	return 0;
	91
	92	err_brelse:
	93	brelse(bhs[0]);
	94	err:
869f58c0	95	fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)", (llu)blocknr);
1da177e4 LT	96	return -EIO;
	97	}
	98
	99	static int fat_ent_bread(struct super_block sb, struct fat_entry fatent,
	100	int offset, sector_t blocknr)
	101	{
8992de4c	102	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
1da177e4 LT	103
1da177e4 LT	104	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
b522412a	105	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
1da177e4 LT	106	fatent->bhs[0] = sb_bread(sb, blocknr);
1da177e4 LT	107	if (!fatent->bhs[0]) {
869f58c0	108	fat_msg(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
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	169
b522412a	170	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
1da177e4	171	if (fatent->nr_bhs == 2)
b522412a	172	mark_buffer_dirty_inode(fatent->bhs[1], fatent->fat_inode);
1da177e4 LT	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);
b522412a	181	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
1da177e4 LT	182	}
	183
	184	static void fat32_ent_put(struct fat_entry *fatent, int new)
	185	{
1da177e4 LT	186	WARN_ON(new & 0xf0000000);
	187	new \|= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
	188	*fatent->u.ent32_p = cpu_to_le32(new);
b522412a	189	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
1da177e4 LT	190	}
	191
	192	static int fat12_ent_next(struct fat_entry *fatent)
	193	{
	194	u8 **ent12_p = fatent->u.ent12_p;
	195	struct buffer_head **bhs = fatent->bhs;
	196	u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
	197
	198	fatent->entry++;
	199	if (fatent->nr_bhs == 1) {
441dff34 CJB	200	WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
	201	(bhs[0]->b_size - 2)));
	202	WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
	203	(bhs[0]->b_size - 1)));
1da177e4 LT	204	if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
	205	ent12_p[0] = nextp - 1;
	206	ent12_p[1] = nextp;
	207	return 1;
	208	}
	209	} else {
441dff34 CJB	210	WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
441dff34 CJB	211	(bhs[0]->b_size - 1)));
1da177e4 LT	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
8992de4c	249	static const struct fatent_operations fat12_ops = {
1da177e4 LT	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
8992de4c	258	static const struct fatent_operations fat16_ops = {
1da177e4 LT	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
8992de4c	267	static const struct fatent_operations fat32_ops = {
1da177e4 LT	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
90b43665 AB	308	static void mark_fsinfo_dirty(struct super_block *sb)
90b43665 AB	309	{
78491189 AB	310	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	311
	312	if (sb->s_flags & MS_RDONLY \|\| sbi->fat_bits != 32)
	313	return;
	314
	315	__mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
90b43665 AB	316	}
90b43665 AB	317
1da177e4 LT	318	static inline int fat_ent_update_ptr(struct super_block *sb,
	319	struct fat_entry *fatent,
	320	int offset, sector_t blocknr)
	321	{
	322	struct msdos_sb_info *sbi = MSDOS_SB(sb);
8992de4c	323	const struct fatent_operations *ops = sbi->fatent_ops;
1da177e4 LT	324	struct buffer_head **bhs = fatent->bhs;
	325
	326	/* Is this fatent's blocks including this entry? */
	327	if (!fatent->nr_bhs \|\| bhs[0]->b_blocknr != blocknr)
	328	return 0;
5e35dd46 OH	329	if (sbi->fat_bits == 12) {
	330	if ((offset + 1) < sb->s_blocksize) {
	331	/* This entry is on bhs[0]. */
	332	if (fatent->nr_bhs == 2) {
	333	brelse(bhs[1]);
	334	fatent->nr_bhs = 1;
	335	}
	336	} else {
	337	/* This entry needs the next block. */
	338	if (fatent->nr_bhs != 2)
	339	return 0;
	340	if (bhs[1]->b_blocknr != (blocknr + 1))
	341	return 0;
	342	}
1da177e4 LT	343	}
	344	ops->ent_set_ptr(fatent, offset);
	345	return 1;
	346	}
	347
	348	int fat_ent_read(struct inode inode, struct fat_entry fatent, int entry)
	349	{
	350	struct super_block *sb = inode->i_sb;
	351	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
8992de4c	352	const struct fatent_operations *ops = sbi->fatent_ops;
1da177e4 LT	353	int err, offset;
	354	sector_t blocknr;
	355
	356	if (entry < FAT_START_ENT \|\| sbi->max_cluster <= entry) {
	357	fatent_brelse(fatent);
85c78591	358	fat_fs_error(sb, "invalid access to FAT (entry 0x%08x)", entry);
1da177e4 LT	359	return -EIO;
	360	}
	361
	362	fatent_set_entry(fatent, entry);
	363	ops->ent_blocknr(sb, entry, &offset, &blocknr);
	364
	365	if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
	366	fatent_brelse(fatent);
	367	err = ops->ent_bread(sb, fatent, offset, blocknr);
	368	if (err)
	369	return err;
	370	}
	371	return ops->ent_get(fatent);
	372	}
	373
	374	/* FIXME: We can write the blocks as more big chunk. */
	375	static int fat_mirror_bhs(struct super_block sb, struct buffer_head *bhs,
	376	int nr_bhs)
	377	{
	378	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	379	struct buffer_head *c_bh;
	380	int err, n, copy;
	381
	382	err = 0;
	383	for (copy = 1; copy < sbi->fats; copy++) {
	384	sector_t backup_fat = sbi->fat_length * copy;
	385
	386	for (n = 0; n < nr_bhs; n++) {
	387	c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
	388	if (!c_bh) {
	389	err = -ENOMEM;
	390	goto error;
	391	}
	392	memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
	393	set_buffer_uptodate(c_bh);
b522412a	394	mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
1da177e4 LT	395	if (sb->s_flags & MS_SYNCHRONOUS)
	396	err = sync_dirty_buffer(c_bh);
	397	brelse(c_bh);
	398	if (err)
	399	goto error;
	400	}
	401	}
	402	error:
	403	return err;
	404	}
	405
	406	int fat_ent_write(struct inode inode, struct fat_entry fatent,
	407	int new, int wait)
	408	{
	409	struct super_block *sb = inode->i_sb;
8992de4c	410	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
1da177e4 LT	411	int err;
	412
	413	ops->ent_put(fatent, new);
	414	if (wait) {
	415	err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
	416	if (err)
	417	return err;
	418	}
	419	return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
	420	}
	421
	422	static inline int fat_ent_next(struct msdos_sb_info *sbi,
	423	struct fat_entry *fatent)
	424	{
	425	if (sbi->fatent_ops->ent_next(fatent)) {
	426	if (fatent->entry < sbi->max_cluster)
	427	return 1;
	428	}
	429	return 0;
	430	}
	431
	432	static inline int fat_ent_read_block(struct super_block *sb,
	433	struct fat_entry *fatent)
	434	{
8992de4c	435	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
1da177e4 LT	436	sector_t blocknr;
	437	int offset;
	438
	439	fatent_brelse(fatent);
	440	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
	441	return ops->ent_bread(sb, fatent, offset, blocknr);
	442	}
	443
	444	static void fat_collect_bhs(struct buffer_head *bhs, int nr_bhs,
	445	struct fat_entry *fatent)
	446	{
	447	int n, i;
	448
	449	for (n = 0; n < fatent->nr_bhs; n++) {
	450	for (i = 0; i < *nr_bhs; i++) {
	451	if (fatent->bhs[n] == bhs[i])
	452	break;
	453	}
	454	if (i == *nr_bhs) {
	455	get_bh(fatent->bhs[n]);
	456	bhs[i] = fatent->bhs[n];
	457	(*nr_bhs)++;
	458	}
	459	}
	460	}
	461
	462	int fat_alloc_clusters(struct inode inode, int cluster, int nr_cluster)
	463	{
	464	struct super_block *sb = inode->i_sb;
	465	struct msdos_sb_info *sbi = MSDOS_SB(sb);
8992de4c	466	const struct fatent_operations *ops = sbi->fatent_ops;
1da177e4 LT	467	struct fat_entry fatent, prev_ent;
	468	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	469	int i, count, err, nr_bhs, idx_clus;
	470
	471	BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2)); /* fixed limit */
	472
	473	lock_fat(sbi);
606e423e OH	474	if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
606e423e OH	475	sbi->free_clusters < nr_cluster) {
1da177e4 LT	476	unlock_fat(sbi);
	477	return -ENOSPC;
	478	}
	479
	480	err = nr_bhs = idx_clus = 0;
	481	count = FAT_START_ENT;
	482	fatent_init(&prev_ent);
	483	fatent_init(&fatent);
	484	fatent_set_entry(&fatent, sbi->prev_free + 1);
	485	while (count < sbi->max_cluster) {
	486	if (fatent.entry >= sbi->max_cluster)
	487	fatent.entry = FAT_START_ENT;
	488	fatent_set_entry(&fatent, fatent.entry);
	489	err = fat_ent_read_block(sb, &fatent);
	490	if (err)
	491	goto out;
	492
	493	/* Find the free entries in a block */
	494	do {
	495	if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
	496	int entry = fatent.entry;
	497
	498	/* make the cluster chain */
	499	ops->ent_put(&fatent, FAT_ENT_EOF);
	500	if (prev_ent.nr_bhs)
	501	ops->ent_put(&prev_ent, entry);
	502
	503	fat_collect_bhs(bhs, &nr_bhs, &fatent);
	504
	505	sbi->prev_free = entry;
	506	if (sbi->free_clusters != -1)
	507	sbi->free_clusters--;
	508
	509	cluster[idx_clus] = entry;
	510	idx_clus++;
	511	if (idx_clus == nr_cluster)
	512	goto out;
	513
	514	/*
	515	* fat_collect_bhs() gets ref-count of bhs,
	516	* so we can still use the prev_ent.
	517	*/
	518	prev_ent = fatent;
	519	}
	520	count++;
	521	if (count == sbi->max_cluster)
	522	break;
	523	} while (fat_ent_next(sbi, &fatent));
	524	}
	525
	526	/* Couldn't allocate the free entries */
	527	sbi->free_clusters = 0;
606e423e	528	sbi->free_clus_valid = 1;
1da177e4 LT	529	err = -ENOSPC;
	530
	531	out:
	532	unlock_fat(sbi);
330fe3c4	533	mark_fsinfo_dirty(sb);
1da177e4 LT	534	fatent_brelse(&fatent);
	535	if (!err) {
	536	if (inode_needs_sync(inode))
	537	err = fat_sync_bhs(bhs, nr_bhs);
	538	if (!err)
	539	err = fat_mirror_bhs(sb, bhs, nr_bhs);
	540	}
	541	for (i = 0; i < nr_bhs; i++)
	542	brelse(bhs[i]);
1da177e4 LT	543
	544	if (err && idx_clus)
	545	fat_free_clusters(inode, cluster[0]);
	546
	547	return err;
	548	}
	549
	550	int fat_free_clusters(struct inode *inode, int cluster)
	551	{
	552	struct super_block *sb = inode->i_sb;
	553	struct msdos_sb_info *sbi = MSDOS_SB(sb);
8992de4c	554	const struct fatent_operations *ops = sbi->fatent_ops;
1da177e4 LT	555	struct fat_entry fatent;
	556	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	557	int i, err, nr_bhs;
330fe3c4	558	int first_cl = cluster, dirty_fsinfo = 0;
1da177e4 LT	559
	560	nr_bhs = 0;
	561	fatent_init(&fatent);
	562	lock_fat(sbi);
	563	do {
	564	cluster = fat_ent_read(inode, &fatent, cluster);
	565	if (cluster < 0) {
	566	err = cluster;
	567	goto error;
	568	} else if (cluster == FAT_ENT_FREE) {
85c78591	569	fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
8e24eea7	570	__func__);
1da177e4 LT	571	err = -EIO;
	572	goto error;
	573	}
	574
681142f9 CH	575	if (sbi->options.discard) {
	576	/*
	577	* Issue discard for the sectors we no longer
	578	* care about, batching contiguous clusters
	579	* into one request
	580	*/
	581	if (cluster != fatent.entry + 1) {
	582	int nr_clus = fatent.entry - first_cl + 1;
	583
	584	sb_issue_discard(sb,
	585	fat_clus_to_blknr(sbi, first_cl),
2cf6d26a	586	nr_clus * sbi->sec_per_clus,
dd3932ed	587	GFP_NOFS, 0);
681142f9 CH	588
	589	first_cl = cluster;
	590	}
8c540a96 DW	591	}
8c540a96 DW	592
1da177e4	593	ops->ent_put(&fatent, FAT_ENT_FREE);
a6bf6b21	594	if (sbi->free_clusters != -1) {
1da177e4	595	sbi->free_clusters++;
330fe3c4	596	dirty_fsinfo = 1;
a6bf6b21	597	}
1da177e4 LT	598
	599	if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
	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	if (err)
	607	goto error;
	608	for (i = 0; i < nr_bhs; i++)
	609	brelse(bhs[i]);
	610	nr_bhs = 0;
	611	}
	612	fat_collect_bhs(bhs, &nr_bhs, &fatent);
	613	} while (cluster != FAT_ENT_EOF);
	614
	615	if (sb->s_flags & MS_SYNCHRONOUS) {
	616	err = fat_sync_bhs(bhs, nr_bhs);
	617	if (err)
	618	goto error;
	619	}
	620	err = fat_mirror_bhs(sb, bhs, nr_bhs);
	621	error:
	622	fatent_brelse(&fatent);
	623	for (i = 0; i < nr_bhs; i++)
	624	brelse(bhs[i]);
	625	unlock_fat(sbi);
330fe3c4 AB	626	if (dirty_fsinfo)
330fe3c4 AB	627	mark_fsinfo_dirty(sb);
1da177e4	628
1da177e4 LT	629	return err;
1da177e4 LT	630	}
7c709d00	631	EXPORT_SYMBOL_GPL(fat_free_clusters);
1da177e4	632
9f966be8 OH	633	/* 128kb is the whole sectors for FAT12 and FAT16 */
	634	#define FAT_READA_SIZE (128 * 1024)
	635
	636	static void fat_ent_reada(struct super_block sb, struct fat_entry fatent,
	637	unsigned long reada_blocks)
	638	{
8992de4c	639	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
9f966be8 OH	640	sector_t blocknr;
	641	int i, offset;
	642
	643	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
	644
	645	for (i = 0; i < reada_blocks; i++)
	646	sb_breadahead(sb, blocknr + i);
	647	}
	648
1da177e4 LT	649	int fat_count_free_clusters(struct super_block *sb)
	650	{
	651	struct msdos_sb_info *sbi = MSDOS_SB(sb);
8992de4c	652	const struct fatent_operations *ops = sbi->fatent_ops;
1da177e4	653	struct fat_entry fatent;
9f966be8	654	unsigned long reada_blocks, reada_mask, cur_block;
1da177e4 LT	655	int err = 0, free;
	656
	657	lock_fat(sbi);
606e423e	658	if (sbi->free_clusters != -1 && sbi->free_clus_valid)
1da177e4 LT	659	goto out;
1da177e4 LT	660
9f966be8 OH	661	reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
	662	reada_mask = reada_blocks - 1;
	663	cur_block = 0;
	664
1da177e4 LT	665	free = 0;
	666	fatent_init(&fatent);
	667	fatent_set_entry(&fatent, FAT_START_ENT);
	668	while (fatent.entry < sbi->max_cluster) {
9f966be8 OH	669	/* readahead of fat blocks */
	670	if ((cur_block & reada_mask) == 0) {
	671	unsigned long rest = sbi->fat_length - cur_block;
	672	fat_ent_reada(sb, &fatent, min(reada_blocks, rest));
	673	}
	674	cur_block++;
	675
1da177e4 LT	676	err = fat_ent_read_block(sb, &fatent);
	677	if (err)
	678	goto out;
	679
	680	do {
	681	if (ops->ent_get(&fatent) == FAT_ENT_FREE)
	682	free++;
	683	} while (fat_ent_next(sbi, &fatent));
	684	}
	685	sbi->free_clusters = free;
606e423e	686	sbi->free_clus_valid = 1;
90b43665	687	mark_fsinfo_dirty(sb);
1da177e4 LT	688	fatent_brelse(&fatent);
	689	out:
	690	unlock_fat(sbi);
	691	return err;
	692	}