fs/fat/fatent.c - kernel/msm-4.9 - Gitiles

 /*
  * 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(!fat_valid_entry(sbi, 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(!fat_valid_entry(sbi, 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 (!fat_valid_entry(sbi, 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;
 }
	/*
	* 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(!fat_valid_entry(sbi, 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(!fat_valid_entry(sbi, 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 (!fat_valid_entry(sbi, 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;
	}