// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  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 "fat.h"

  #include <linux/iversion.h>

  
  /*

   * fat_fs_error reports a file system problem that might indicate fa data
   * corruption/inconsistency. Depending on 'errors' mount option the
   * panic() is called, or error message is printed FAT and nothing is done,
   * or filesystem is remounted read-only (default behavior).
   * In case the file system is remounted read-only, it can be made writable
   * again by remounting it.

   */

  void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...)

  {

  	struct fat_mount_options *opts = &MSDOS_SB(sb)->options;

  	va_list args;

  	struct va_format vaf;

  	if (report) {

  		va_start(args, fmt);

  		vaf.fmt = fmt;
  		vaf.va = &args;

  		fat_msg(sb, KERN_ERR, "error, %pV", &vaf);

  		va_end(args);

  	}

  	if (opts->errors == FAT_ERRORS_PANIC)

  		panic("FAT-fs (%s): fs panic from previous error
  ", sb->s_id);

  	else if (opts->errors == FAT_ERRORS_RO && !sb_rdonly(sb)) {

  		sb->s_flags |= SB_RDONLY;

  		fat_msg(sb, KERN_ERR, "Filesystem has been set read-only");

  	}
  }

  EXPORT_SYMBOL_GPL(__fat_fs_error);

  /**
   * fat_msg() - print preformated FAT specific messages. Every thing what is
   * not fat_fs_error() should be fat_msg().
   */
  void fat_msg(struct super_block *sb, const char *level, const char *fmt, ...)
  {
  	struct va_format vaf;
  	va_list args;
  
  	va_start(args, fmt);
  	vaf.fmt = fmt;
  	vaf.va = &args;
  	printk("%sFAT-fs (%s): %pV
  ", level, sb->s_id, &vaf);
  	va_end(args);
  }

  /* Flushes the number of free clusters on FAT32 */
  /* XXX: Need to write one per FSINFO block.  Currently only writes 1 */

  int 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 (!is_fat32(sbi))

  		return 0;

  
  	bh = sb_bread(sb, sbi->fsinfo_sector);
  	if (bh == NULL) {

  		fat_msg(sb, KERN_ERR, "bread failed in fat_clusters_flush");

  		return -EIO;

  	}
  
  	fsinfo = (struct fat_boot_fsinfo *)bh->b_data;
  	/* Sanity check */
  	if (!IS_FSINFO(fsinfo)) {

  		fat_msg(sb, KERN_ERR, "Invalid FSINFO signature: "
  		       "0x%08x, 0x%08x (sector = %lu)",

  		       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);

  
  	return 0;

  }
  
  /*
   * fat_chain_add() adds a new cluster to the chain of clusters represented
   * by inode.
   */
  int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster)
  {
  	struct super_block *sb = inode->i_sb;
  	struct msdos_sb_info *sbi = MSDOS_SB(sb);
  	int ret, new_fclus, last;
  
  	/*
  	 * 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).
  	 */
  	last = new_fclus = 0;
  	if (MSDOS_I(inode)->i_start) {
  		int fclus, dclus;
  
  		ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
  		if (ret < 0)
  			return ret;
  		new_fclus = fclus + 1;
  		last = dclus;
  	}
  
  	/* add new one to the last of the cluster chain */
  	if (last) {
  		struct fat_entry fatent;
  
  		fatent_init(&fatent);
  		ret = fat_ent_read(inode, &fatent, last);
  		if (ret >= 0) {
  			int wait = inode_needs_sync(inode);
  			ret = fat_ent_write(inode, &fatent, new_dclus, wait);
  			fatent_brelse(&fatent);
  		}
  		if (ret < 0)
  			return ret;

  		/*
  		 * FIXME:Although we can add this cache, fat_cache_add() is
  		 * assuming to be called after linear search with fat_cache_id.
  		 */

  //		fat_cache_add(inode, new_fclus, new_dclus);
  	} else {
  		MSDOS_I(inode)->i_start = new_dclus;
  		MSDOS_I(inode)->i_logstart = new_dclus;
  		/*

  		 * Since generic_write_sync() synchronizes regular files later,
  		 * we sync here only directories.

  		 */
  		if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode)) {
  			ret = fat_sync_inode(inode);
  			if (ret)
  				return ret;
  		} else
  			mark_inode_dirty(inode);
  	}
  	if (new_fclus != (inode->i_blocks >> (sbi->cluster_bits - 9))) {

  		fat_fs_error(sb, "clusters badly computed (%d != %llu)",

  			     new_fclus,
  			     (llu)(inode->i_blocks >> (sbi->cluster_bits - 9)));

  		fat_cache_inval_inode(inode);
  	}
  	inode->i_blocks += nr_cluster << (sbi->cluster_bits - 9);
  
  	return 0;
  }

  /*
   * The epoch of FAT timestamp is 1980.
   *     :  bits :     value
   * date:  0 -  4: day	(1 -  31)
   * date:  5 -  8: month	(1 -  12)
   * date:  9 - 15: year	(0 - 127) from 1980
   * time:  0 -  4: sec	(0 -  29) 2sec counts
   * time:  5 - 10: min	(0 -  59)
   * time: 11 - 15: hour	(0 -  23)
   */
  #define SECS_PER_MIN	60
  #define SECS_PER_HOUR	(60 * 60)
  #define SECS_PER_DAY	(SECS_PER_HOUR * 24)

  /* days between 1.1.70 and 1.1.80 (2 leap days) */
  #define DAYS_DELTA	(365 * 10 + 2)
  /* 120 (2100 - 1980) isn't leap year */
  #define YEAR_2100	120
  #define IS_LEAP_YEAR(y)	(!((y) & 3) && (y) != YEAR_2100)

  /* Linear day numbers of the respective 1sts in non-leap years. */

  static long days_in_year[] = {

  	/* Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sep  Oct  Nov  Dec */
  	0,   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0,

  };

  static inline int fat_tz_offset(struct msdos_sb_info *sbi)
  {
  	return (sbi->options.tz_set ?
  	       -sbi->options.time_offset :
  	       sys_tz.tz_minuteswest) * SECS_PER_MIN;
  }

  /* Convert a FAT time/date pair to a UNIX date (seconds since 1 1 70). */

  void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,

  		       __le16 __time, __le16 __date, u8 time_cs)

  {

  	u16 time = le16_to_cpu(__time), date = le16_to_cpu(__date);

  	time64_t second;
  	long day, leap_day, month, year;

  	year  = date >> 9;
  	month = max(1, (date >> 5) & 0xf);
  	day   = max(1, date & 0x1f) - 1;
  
  	leap_day = (year + 3) / 4;
  	if (year > YEAR_2100)		/* 2100 isn't leap year */
  		leap_day--;
  	if (IS_LEAP_YEAR(year) && month > 2)
  		leap_day++;
  
  	second =  (time & 0x1f) << 1;
  	second += ((time >> 5) & 0x3f) * SECS_PER_MIN;
  	second += (time >> 11) * SECS_PER_HOUR;

  	second += (time64_t)(year * 365 + leap_day

  		   + days_in_year[month] + day
  		   + DAYS_DELTA) * SECS_PER_DAY;

  	second += fat_tz_offset(sbi);

  
  	if (time_cs) {
  		ts->tv_sec = second + (time_cs / 100);
  		ts->tv_nsec = (time_cs % 100) * 10000000;
  	} else {
  		ts->tv_sec = second;
  		ts->tv_nsec = 0;
  	}

  }

  /* Convert linear UNIX date to a FAT time/date pair. */

  void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,

  		       __le16 *time, __le16 *date, u8 *time_cs)

  {

  	struct tm tm;

  	time64_to_tm(ts->tv_sec, -fat_tz_offset(sbi), &tm);

  	/*  FAT can only support year between 1980 to 2107 */
  	if (tm.tm_year < 1980 - 1900) {

  		*time = 0;
  		*date = cpu_to_le16((0 << 9) | (1 << 5) | 1);
  		if (time_cs)
  			*time_cs = 0;
  		return;
  	}

  	if (tm.tm_year > 2107 - 1900) {

  		*time = cpu_to_le16((23 << 11) | (59 << 5) | 29);
  		*date = cpu_to_le16((127 << 9) | (12 << 5) | 31);
  		if (time_cs)
  			*time_cs = 199;
  		return;
  	}

  	/* from 1900 -> from 1980 */
  	tm.tm_year -= 80;
  	/* 0~11 -> 1~12 */
  	tm.tm_mon++;
  	/* 0~59 -> 0~29(2sec counts) */
  	tm.tm_sec >>= 1;

  	*time = cpu_to_le16(tm.tm_hour << 11 | tm.tm_min << 5 | tm.tm_sec);
  	*date = cpu_to_le16(tm.tm_year << 9 | tm.tm_mon << 5 | tm.tm_mday);

  	if (time_cs)
  		*time_cs = (ts->tv_sec & 1) * 100 + ts->tv_nsec / 10000000;
  }
  EXPORT_SYMBOL_GPL(fat_time_unix2fat);

  static inline struct timespec64 fat_timespec64_trunc_2secs(struct timespec64 ts)
  {
  	return (struct timespec64){ ts.tv_sec & ~1ULL, 0 };
  }
  /*
   * truncate the various times with appropriate granularity:
   *   root inode:
   *     all times always 0
   *   all other inodes:
   *     mtime - 2 seconds
   *     ctime
   *       msdos - 2 seconds
   *       vfat  - 10 milliseconds
   *     atime - 24 hours (00:00:00 in local timezone)
   */
  int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
  {
  	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
  	struct timespec64 ts;
  
  	if (inode->i_ino == MSDOS_ROOT_INO)
  		return 0;
  
  	if (now == NULL) {
  		now = &ts;
  		ts = current_time(inode);
  	}
  
  	if (flags & S_ATIME) {
  		/* to localtime */
  		time64_t seconds = now->tv_sec - fat_tz_offset(sbi);
  		s32 remainder;
  
  		div_s64_rem(seconds, SECS_PER_DAY, &remainder);
  		/* to day boundary, and back to unix time */
  		seconds = seconds + fat_tz_offset(sbi) - remainder;
  
  		inode->i_atime = (struct timespec64){ seconds, 0 };
  	}
  	if (flags & S_CTIME) {
  		if (sbi->options.isvfat)
  			inode->i_ctime = timespec64_trunc(*now, 10000000);
  		else
  			inode->i_ctime = fat_timespec64_trunc_2secs(*now);
  	}
  	if (flags & S_MTIME)
  		inode->i_mtime = fat_timespec64_trunc_2secs(*now);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(fat_truncate_time);
  
  int fat_update_time(struct inode *inode, struct timespec64 *now, int flags)
  {
  	int iflags = I_DIRTY_TIME;
  	bool dirty = false;
  
  	if (inode->i_ino == MSDOS_ROOT_INO)
  		return 0;
  
  	fat_truncate_time(inode, now, flags);
  	if (flags & S_VERSION)
  		dirty = inode_maybe_inc_iversion(inode, false);
  	if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
  	    !(inode->i_sb->s_flags & SB_LAZYTIME))
  		dirty = true;
  
  	if (dirty)
  		iflags |= I_DIRTY_SYNC;
  	__mark_inode_dirty(inode, iflags);
  	return 0;
  }
  EXPORT_SYMBOL_GPL(fat_update_time);

  int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
  {

  	int i, err = 0;

  	for (i = 0; i < nr_bhs; i++)

  		write_dirty_buffer(bhs[i], 0);

  	for (i = 0; i < nr_bhs; i++) {
  		wait_on_buffer(bhs[i]);

  		if (!err && !buffer_uptodate(bhs[i]))

  			err = -EIO;
  	}
  	return err;
  }