exfat: add misc operations

This adds the implementation of misc operations for exfat.
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/exfat/misc.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  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)
+ * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
+ */
+
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/buffer_head.h>
+
+#include "exfat_raw.h"
+#include "exfat_fs.h"
+
+/*
+ * exfat_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 __exfat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
+{
+	struct exfat_mount_options *opts = &EXFAT_SB(sb)->options;
+	va_list args;
+	struct va_format vaf;
+
+	if (report) {
+		va_start(args, fmt);
+		vaf.fmt = fmt;
+		vaf.va = &args;
+		exfat_msg(sb, KERN_ERR, "error, %pV\n", &vaf);
+		va_end(args);
+	}
+
+	if (opts->errors == EXFAT_ERRORS_PANIC) {
+		panic("exFAT-fs (%s): fs panic from previous error\n",
+			sb->s_id);
+	} else if (opts->errors == EXFAT_ERRORS_RO && !sb_rdonly(sb)) {
+		sb->s_flags |= SB_RDONLY;
+		exfat_msg(sb, KERN_ERR, "Filesystem has been set read-only");
+	}
+}
+
+/*
+ * exfat_msg() - print preformated EXFAT specific messages.
+ * All logs except what uses exfat_fs_error() should be written by exfat_msg()
+ */
+void exfat_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;
+	/* level means KERN_ pacility level */
+	printk("%sexFAT-fs (%s): %pV\n", level, sb->s_id, &vaf);
+	va_end(args);
+}
+
+#define SECS_PER_MIN    (60)
+#define TIMEZONE_SEC(x)	((x) * 15 * SECS_PER_MIN)
+
+static void exfat_adjust_tz(struct timespec64 *ts, u8 tz_off)
+{
+	if (tz_off <= 0x3F)
+		ts->tv_sec -= TIMEZONE_SEC(tz_off);
+	else /* 0x40 <= (tz_off & 0x7F) <=0x7F */
+		ts->tv_sec += TIMEZONE_SEC(0x80 - tz_off);
+}
+
+/* Convert a EXFAT time/date pair to a UNIX date (seconds since 1 1 70). */
+void exfat_get_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
+		u8 tz, __le16 time, __le16 date, u8 time_ms)
+{
+	u16 t = le16_to_cpu(time);
+	u16 d = le16_to_cpu(date);
+
+	ts->tv_sec = mktime64(1980 + (d >> 9), d >> 5 & 0x000F, d & 0x001F,
+			      t >> 11, (t >> 5) & 0x003F, (t & 0x001F) << 1);
+
+
+	/* time_ms field represent 0 ~ 199(1990 ms) */
+	if (time_ms) {
+		ts->tv_sec += time_ms / 100;
+		ts->tv_nsec = (time_ms % 100) * 10 * NSEC_PER_MSEC;
+	}
+
+	if (tz & EXFAT_TZ_VALID)
+		/* Adjust timezone to UTC0. */
+		exfat_adjust_tz(ts, tz & ~EXFAT_TZ_VALID);
+	else
+		/* Convert from local time to UTC using time_offset. */
+		ts->tv_sec -= sbi->options.time_offset * SECS_PER_MIN;
+}
+
+/* Convert linear UNIX date to a EXFAT time/date pair. */
+void exfat_set_entry_time(struct exfat_sb_info *sbi, struct timespec64 *ts,
+		u8 *tz, __le16 *time, __le16 *date, u8 *time_ms)
+{
+	struct tm tm;
+	u16 t, d;
+
+	time64_to_tm(ts->tv_sec, 0, &tm);
+	t = (tm.tm_hour << 11) | (tm.tm_min << 5) | (tm.tm_sec >> 1);
+	d = ((tm.tm_year - 80) <<  9) | ((tm.tm_mon + 1) << 5) | tm.tm_mday;
+
+	*time = cpu_to_le16(t);
+	*date = cpu_to_le16(d);
+
+	/* time_ms field represent 0 ~ 199(1990 ms) */
+	if (time_ms)
+		*time_ms = (tm.tm_sec & 1) * 100 +
+			ts->tv_nsec / (10 * NSEC_PER_MSEC);
+
+	/*
+	 * Record 00h value for OffsetFromUtc field and 1 value for OffsetValid
+	 * to indicate that local time and UTC are the same.
+	 */
+	*tz = EXFAT_TZ_VALID;
+}
+
+unsigned short exfat_calc_chksum_2byte(void *data, int len,
+		unsigned short chksum, int type)
+{
+	int i;
+	unsigned char *c = (unsigned char *)data;
+
+	for (i = 0; i < len; i++, c++) {
+		if (((i == 2) || (i == 3)) && (type == CS_DIR_ENTRY))
+			continue;
+		chksum = (((chksum & 1) << 15) | ((chksum & 0xFFFE) >> 1)) +
+			(unsigned short)*c;
+	}
+	return chksum;
+}
+
+void exfat_update_bh(struct super_block *sb, struct buffer_head *bh, int sync)
+{
+	set_bit(EXFAT_SB_DIRTY, &EXFAT_SB(sb)->s_state);
+	set_buffer_uptodate(bh);
+	mark_buffer_dirty(bh);
+
+	if (sync)
+		sync_dirty_buffer(bh);
+}
+
+void exfat_chain_set(struct exfat_chain *ec, unsigned int dir,
+		unsigned int size, unsigned char flags)
+{
+	ec->dir = dir;
+	ec->size = size;
+	ec->flags = flags;
+}
+
+void exfat_chain_dup(struct exfat_chain *dup, struct exfat_chain *ec)
+{
+	return exfat_chain_set(dup, ec->dir, ec->size, ec->flags);
+}