fs/fat/misc.c - third_party/linux - Git at Google

 /*
  *  linux/fs/fat/misc.c
  *
  *  Written 1992,1993 by Werner Almesberger
  *  22/11/2000 - Fixed fat_date_unix2dos for dates earlier than 01/01/1980
  *		 and date_dos2unix for date==0 by Igor Zhbanov(bsg@uniyar.ac.ru)
  */

 #include <linux/module.h>
 #include <linux/fs.h>
 #include <linux/msdos_fs.h>
 #include <linux/buffer_head.h>

 /*
  * fat_fs_panic reports a severe file system problem and sets the file system
  * read-only. The file system can be made writable again by remounting it.
  */
 void fat_fs_panic(struct super_block *s, const char *fmt, ...)
 {
 	va_list args;

 	printk(KERN_ERR "FAT: Filesystem panic (dev %s)\n", s->s_id);

 	printk(KERN_ERR "    ");
 	va_start(args, fmt);
 	vprintk(fmt, args);
 	va_end(args);
 	printk("\n");

 	if (!(s->s_flags & MS_RDONLY)) {
 		s->s_flags |= MS_RDONLY;
 		printk(KERN_ERR "    File system has been set read-only\n");
 	}
 }

 void lock_fat(struct super_block *sb)
 {
 	down(&(MSDOS_SB(sb)->fat_lock));
 }

 void unlock_fat(struct super_block *sb)
 {
 	up(&(MSDOS_SB(sb)->fat_lock));
 }

 /* Flushes the number of free clusters on FAT32 */
 /* XXX: Need to write one per FSINFO block.  Currently only writes 1 */
 void fat_clusters_flush(struct super_block *sb)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 	struct buffer_head *bh;
 	struct fat_boot_fsinfo *fsinfo;

 	if (sbi->fat_bits != 32)
 		return;

 	bh = sb_bread(sb, sbi->fsinfo_sector);
 	if (bh == NULL) {
 		printk(KERN_ERR "FAT bread failed in fat_clusters_flush\n");
 		return;
 	}

 	fsinfo = (struct fat_boot_fsinfo *)bh->b_data;
 	/* Sanity check */
 	if (!IS_FSINFO(fsinfo)) {
 		printk(KERN_ERR "FAT: Did not find valid FSINFO signature.\n"
 		       "     Found signature1 0x%08x signature2 0x%08x"
 		       " (sector = %lu)\n",
 		       le32_to_cpu(fsinfo->signature1),
 		       le32_to_cpu(fsinfo->signature2),
 		       sbi->fsinfo_sector);
 	} else {
 		if (sbi->free_clusters != -1)
 			fsinfo->free_clusters = cpu_to_le32(sbi->free_clusters);
 		if (sbi->prev_free != -1)
 			fsinfo->next_cluster = cpu_to_le32(sbi->prev_free);
 		mark_buffer_dirty(bh);
 	}
 	brelse(bh);
 }

 /*
  * fat_add_cluster tries to allocate a new cluster and adds it to the
  * file represented by inode.
  */
 int fat_add_cluster(struct inode *inode)
 {
 	struct super_block *sb = inode->i_sb;
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 	int ret, count, limit, new_dclus, new_fclus, last;
 	int cluster_bits = sbi->cluster_bits;

 	/*
 	 * We must locate the last cluster of the file to add this new
 	 * one (new_dclus) to the end of the link list (the FAT).
 	 *
 	 * In order to confirm that the cluster chain is valid, we
 	 * find out EOF first.
 	 */
 	last = new_fclus = 0;
 	if (MSDOS_I(inode)->i_start) {
 		int ret, fclus, dclus;

 		ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
 		if (ret < 0)
 			return ret;
 		new_fclus = fclus + 1;
 		last = dclus;
 	}

 	/* find free FAT entry */
 	lock_fat(sb);

 	if (sbi->free_clusters == 0) {
 		unlock_fat(sb);
 		return -ENOSPC;
 	}

 	limit = sbi->max_cluster;
 	new_dclus = sbi->prev_free + 1;
 	for (count = FAT_START_ENT; count < limit; count++, new_dclus++) {
 		new_dclus = new_dclus % limit;
 		if (new_dclus < FAT_START_ENT)
 			new_dclus = FAT_START_ENT;

 		ret = fat_access(sb, new_dclus, -1);
 		if (ret < 0) {
 			unlock_fat(sb);
 			return ret;
 		} else if (ret == FAT_ENT_FREE)
 			break;
 	}
 	if (count >= limit) {
 		sbi->free_clusters = 0;
 		unlock_fat(sb);
 		return -ENOSPC;
 	}

 	ret = fat_access(sb, new_dclus, FAT_ENT_EOF);
 	if (ret < 0) {
 		unlock_fat(sb);
 		return ret;
 	}

 	sbi->prev_free = new_dclus;
 	if (sbi->free_clusters != -1)
 		sbi->free_clusters--;
 	fat_clusters_flush(sb);

 	unlock_fat(sb);

 	/* add new one to the last of the cluster chain */
 	if (last) {
 		ret = fat_access(sb, last, new_dclus);
 		if (ret < 0)
 			return ret;
 //		fat_cache_add(inode, new_fclus, new_dclus);
 	} else {
 		MSDOS_I(inode)->i_start = new_dclus;
 		MSDOS_I(inode)->i_logstart = new_dclus;
 		mark_inode_dirty(inode);
 	}
 	if (new_fclus != (inode->i_blocks >> (cluster_bits - 9))) {
 		fat_fs_panic(sb, "clusters badly computed (%d != %lu)",
 			new_fclus, inode->i_blocks >> (cluster_bits - 9));
 		fat_cache_inval_inode(inode);
 	}
 	inode->i_blocks += sbi->cluster_size >> 9;

 	return new_dclus;
 }

 extern struct timezone sys_tz;

 /* Linear day numbers of the respective 1sts in non-leap years. */
 static int day_n[] = {
    /* Jan  Feb  Mar  Apr   May  Jun  Jul  Aug  Sep  Oct  Nov  Dec */
 	0,  31,  59,  90,  120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0, 0
 };

 /* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */
 int date_dos2unix(unsigned short time, unsigned short date)
 {
 	int month, year, secs;

 	/*
 	 * first subtract and mask after that... Otherwise, if
 	 * date == 0, bad things happen
 	 */
 	month = ((date >> 5) - 1) & 15;
 	year = date >> 9;
 	secs = (time & 31)*2+60*((time >> 5) & 63)+(time >> 11)*3600+86400*
 	    ((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
 	    month < 2 ? 1 : 0)+3653);
 			/* days since 1.1.70 plus 80's leap day */
 	secs += sys_tz.tz_minuteswest*60;
 	return secs;
 }

 /* Convert linear UNIX date to a MS-DOS time/date pair. */
 void fat_date_unix2dos(int unix_date, __le16 *time, __le16 *date)
 {
 	int day, year, nl_day, month;

 	unix_date -= sys_tz.tz_minuteswest*60;

 	/* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
 	if (unix_date < 315532800)
 		unix_date = 315532800;

 	*time = cpu_to_le16((unix_date % 60)/2+(((unix_date/60) % 60) << 5)+
 	    (((unix_date/3600) % 24) << 11));
 	day = unix_date/86400-3652;
 	year = day/365;
 	if ((year+3)/4+365*year > day)
 		year--;
 	day -= (year+3)/4+365*year;
 	if (day == 59 && !(year & 3)) {
 		nl_day = day;
 		month = 2;
 	} else {
 		nl_day = (year & 3) || day <= 59 ? day : day-1;
 		for (month = 0; month < 12; month++) {
 			if (day_n[month] > nl_day)
 				break;
 		}
 	}
 	*date = cpu_to_le16(nl_day-day_n[month-1]+1+(month << 5)+(year << 9));
 }

 EXPORT_SYMBOL(fat_date_unix2dos);

 /* Returns the inode number of the directory entry at offset pos. If bh is
    non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
    returned in bh.
    AV. Most often we do it item-by-item. Makes sense to optimize.
    AV. OK, there we go: if both bh and de are non-NULL we assume that we just
    AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
    AV. It's done in fat_get_entry() (inlined), here the slow case lives.
    AV. Additionally, when we return -1 (i.e. reached the end of directory)
    AV. we make bh NULL.
  */

 int fat__get_entry(struct inode *dir, loff_t *pos, struct buffer_head **bh,
 		   struct msdos_dir_entry **de, loff_t *i_pos)
 {
 	struct super_block *sb = dir->i_sb;
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 	sector_t phys, iblock;
 	loff_t offset;
 	int err;

 next:
 	offset = *pos;
 	if (*bh)
 		brelse(*bh);

 	*bh = NULL;
 	iblock = *pos >> sb->s_blocksize_bits;
 	err = fat_bmap(dir, iblock, &phys);
 	if (err || !phys)
 		return -1;	/* beyond EOF or error */

 	*bh = sb_bread(sb, phys);
 	if (*bh == NULL) {
 		printk(KERN_ERR "FAT: Directory bread(block %llu) failed\n",
 		       (unsigned long long)phys);
 		/* skip this block */
 		*pos = (iblock + 1) << sb->s_blocksize_bits;
 		goto next;
 	}

 	offset &= sb->s_blocksize - 1;
 	*pos += sizeof(struct msdos_dir_entry);
 	*de = (struct msdos_dir_entry *)((*bh)->b_data + offset);
 	*i_pos = ((loff_t)phys << sbi->dir_per_block_bits) + (offset >> MSDOS_DIR_BITS);

 	return 0;
 }

 EXPORT_SYMBOL(fat__get_entry);
	/*
	* linux/fs/fat/misc.c
	*
	* Written 1992,1993 by Werner Almesberger
	* 22/11/2000 - Fixed fat_date_unix2dos for dates earlier than 01/01/1980
	* and date_dos2unix for date==0 by Igor Zhbanov(bsg@uniyar.ac.ru)
	*/

	#include <linux/module.h>
	#include <linux/fs.h>
	#include <linux/msdos_fs.h>
	#include <linux/buffer_head.h>

	/*
	* fat_fs_panic reports a severe file system problem and sets the file system
	* read-only. The file system can be made writable again by remounting it.
	*/
	void fat_fs_panic(struct super_block s, const char fmt, ...)
	{
	va_list args;

	printk(KERN_ERR "FAT: Filesystem panic (dev %s)\n", s->s_id);

	printk(KERN_ERR " ");
	va_start(args, fmt);
	vprintk(fmt, args);
	va_end(args);
	printk("\n");

	if (!(s->s_flags & MS_RDONLY)) {
	s->s_flags \|= MS_RDONLY;
	printk(KERN_ERR " File system has been set read-only\n");
	}
	}

	void lock_fat(struct super_block *sb)
	{
	down(&(MSDOS_SB(sb)->fat_lock));
	}

	void unlock_fat(struct super_block *sb)
	{
	up(&(MSDOS_SB(sb)->fat_lock));
	}

	/* Flushes the number of free clusters on FAT32 */
	/* XXX: Need to write one per FSINFO block. Currently only writes 1 */
	void fat_clusters_flush(struct super_block *sb)
	{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct buffer_head *bh;
	struct fat_boot_fsinfo *fsinfo;

	if (sbi->fat_bits != 32)
	return;

	bh = sb_bread(sb, sbi->fsinfo_sector);
	if (bh == NULL) {
	printk(KERN_ERR "FAT bread failed in fat_clusters_flush\n");
	return;
	}

	fsinfo = (struct fat_boot_fsinfo *)bh->b_data;
	/* Sanity check */
	if (!IS_FSINFO(fsinfo)) {
	printk(KERN_ERR "FAT: Did not find valid FSINFO signature.\n"
	" Found signature1 0x%08x signature2 0x%08x"
	" (sector = %lu)\n",
	le32_to_cpu(fsinfo->signature1),
	le32_to_cpu(fsinfo->signature2),
	sbi->fsinfo_sector);
	} else {
	if (sbi->free_clusters != -1)
	fsinfo->free_clusters = cpu_to_le32(sbi->free_clusters);
	if (sbi->prev_free != -1)
	fsinfo->next_cluster = cpu_to_le32(sbi->prev_free);
	mark_buffer_dirty(bh);
	}
	brelse(bh);
	}

	/*
	* fat_add_cluster tries to allocate a new cluster and adds it to the
	* file represented by inode.
	*/
	int fat_add_cluster(struct inode *inode)
	{
	struct super_block *sb = inode->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	int ret, count, limit, new_dclus, new_fclus, last;
	int cluster_bits = sbi->cluster_bits;

	/*
	* We must locate the last cluster of the file to add this new
	* one (new_dclus) to the end of the link list (the FAT).
	*
	* In order to confirm that the cluster chain is valid, we
	* find out EOF first.
	*/
	last = new_fclus = 0;
	if (MSDOS_I(inode)->i_start) {
	int ret, fclus, dclus;

	ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
	if (ret < 0)
	return ret;
	new_fclus = fclus + 1;
	last = dclus;
	}

	/* find free FAT entry */
	lock_fat(sb);

	if (sbi->free_clusters == 0) {
	unlock_fat(sb);
	return -ENOSPC;
	}

	limit = sbi->max_cluster;
	new_dclus = sbi->prev_free + 1;
	for (count = FAT_START_ENT; count < limit; count++, new_dclus++) {
	new_dclus = new_dclus % limit;
	if (new_dclus < FAT_START_ENT)
	new_dclus = FAT_START_ENT;

	ret = fat_access(sb, new_dclus, -1);
	if (ret < 0) {
	unlock_fat(sb);
	return ret;
	} else if (ret == FAT_ENT_FREE)
	break;
	}
	if (count >= limit) {
	sbi->free_clusters = 0;
	unlock_fat(sb);
	return -ENOSPC;
	}

	ret = fat_access(sb, new_dclus, FAT_ENT_EOF);
	if (ret < 0) {
	unlock_fat(sb);
	return ret;
	}

	sbi->prev_free = new_dclus;
	if (sbi->free_clusters != -1)
	sbi->free_clusters--;
	fat_clusters_flush(sb);

	unlock_fat(sb);

	/* add new one to the last of the cluster chain */
	if (last) {
	ret = fat_access(sb, last, new_dclus);
	if (ret < 0)
	return ret;
	// fat_cache_add(inode, new_fclus, new_dclus);
	} else {
	MSDOS_I(inode)->i_start = new_dclus;
	MSDOS_I(inode)->i_logstart = new_dclus;
	mark_inode_dirty(inode);
	}
	if (new_fclus != (inode->i_blocks >> (cluster_bits - 9))) {
	fat_fs_panic(sb, "clusters badly computed (%d != %lu)",
	new_fclus, inode->i_blocks >> (cluster_bits - 9));
	fat_cache_inval_inode(inode);
	}
	inode->i_blocks += sbi->cluster_size >> 9;

	return new_dclus;
	}

	extern struct timezone sys_tz;

	/* Linear day numbers of the respective 1sts in non-leap years. */
	static int day_n[] = {
	/* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec */
	0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0, 0
	};

	/* Convert a MS-DOS time/date pair to a UNIX date (seconds since 1 1 70). */
	int date_dos2unix(unsigned short time, unsigned short date)
	{
	int month, year, secs;

	/*
	* first subtract and mask after that... Otherwise, if
	* date == 0, bad things happen
	*/
	month = ((date >> 5) - 1) & 15;
	year = date >> 9;
	secs = (time & 31)2+60((time >> 5) & 63)+(time >> 11)3600+86400
	((date & 31)-1+day_n[month]+(year/4)+year*365-((year & 3) == 0 &&
	month < 2 ? 1 : 0)+3653);
	/* days since 1.1.70 plus 80's leap day */
	secs += sys_tz.tz_minuteswest*60;
	return secs;
	}

	/* Convert linear UNIX date to a MS-DOS time/date pair. */
	void fat_date_unix2dos(int unix_date, __le16 time, __le16 date)
	{
	int day, year, nl_day, month;

	unix_date -= sys_tz.tz_minuteswest*60;

	/* Jan 1 GMT 00:00:00 1980. But what about another time zone? */
	if (unix_date < 315532800)
	unix_date = 315532800;

	*time = cpu_to_le16((unix_date % 60)/2+(((unix_date/60) % 60) << 5)+
	(((unix_date/3600) % 24) << 11));
	day = unix_date/86400-3652;
	year = day/365;
	if ((year+3)/4+365*year > day)
	year--;
	day -= (year+3)/4+365*year;
	if (day == 59 && !(year & 3)) {
	nl_day = day;
	month = 2;
	} else {
	nl_day = (year & 3) \|\| day <= 59 ? day : day-1;
	for (month = 0; month < 12; month++) {
	if (day_n[month] > nl_day)
	break;
	}
	}
	*date = cpu_to_le16(nl_day-day_n[month-1]+1+(month << 5)+(year << 9));
	}

	EXPORT_SYMBOL(fat_date_unix2dos);

	/* Returns the inode number of the directory entry at offset pos. If bh is
	non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
	returned in bh.
	AV. Most often we do it item-by-item. Makes sense to optimize.
	AV. OK, there we go: if both bh and de are non-NULL we assume that we just
	AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
	AV. It's done in fat_get_entry() (inlined), here the slow case lives.
	AV. Additionally, when we return -1 (i.e. reached the end of directory)
	AV. we make bh NULL.
	*/

	int fat__get_entry(struct inode dir, loff_t pos, struct buffer_head **bh,
	struct msdos_dir_entry *de, loff_t i_pos)
	{
	struct super_block *sb = dir->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	sector_t phys, iblock;
	loff_t offset;
	int err;

	next:
	offset = *pos;
	if (*bh)
	brelse(*bh);

	*bh = NULL;
	iblock = *pos >> sb->s_blocksize_bits;
	err = fat_bmap(dir, iblock, &phys);
	if (err \|\| !phys)
	return -1; /* beyond EOF or error */

	*bh = sb_bread(sb, phys);
	if (*bh == NULL) {
	printk(KERN_ERR "FAT: Directory bread(block %llu) failed\n",
	(unsigned long long)phys);
	/* skip this block */
	*pos = (iblock + 1) << sb->s_blocksize_bits;
	goto next;
	}

	offset &= sb->s_blocksize - 1;
	*pos += sizeof(struct msdos_dir_entry);
	de = (struct msdos_dir_entry )((*bh)->b_data + offset);
	*i_pos = ((loff_t)phys << sbi->dir_per_block_bits) + (offset >> MSDOS_DIR_BITS);

	return 0;
	}

	EXPORT_SYMBOL(fat__get_entry);