add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/fs/fat/misc.c
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@@ -1,3 +1,4 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  *  linux/fs/fat/misc.c
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  *
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@@ -7,6 +8,7 @@
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  */
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 #include "fat.h"
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+#include <linux/iversion.h>
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 /*
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  * fat_fs_error reports a file system problem that might indicate fa data
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@@ -63,7 +65,7 @@
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 	struct buffer_head *bh;
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 	struct fat_boot_fsinfo *fsinfo;
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-	if (sbi->fat_bits != 32)
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+	if (!is_fat32(sbi))
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 		return 0;
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 	bh = sb_bread(sb, sbi->fsinfo_sector);
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@@ -185,6 +187,13 @@
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 	0,   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0,
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 };
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+static inline int fat_tz_offset(struct msdos_sb_info *sbi)
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+{
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+	return (sbi->options.tz_set ?
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+	       -sbi->options.time_offset :
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+	       sys_tz.tz_minuteswest) * SECS_PER_MIN;
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+}
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+
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 /* Convert a FAT time/date pair to a UNIX date (seconds since 1 1 70). */
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 void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
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 		       __le16 __time, __le16 __date, u8 time_cs)
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@@ -210,10 +219,7 @@
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 		   + days_in_year[month] + day
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 		   + DAYS_DELTA) * SECS_PER_DAY;
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-	if (!sbi->options.tz_set)
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-		second += sys_tz.tz_minuteswest * SECS_PER_MIN;
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-	else
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-		second -= sbi->options.time_offset * SECS_PER_MIN;
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+	second += fat_tz_offset(sbi);
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 	if (time_cs) {
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 		ts->tv_sec = second + (time_cs / 100);
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@@ -229,9 +235,7 @@
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 		       __le16 *time, __le16 *date, u8 *time_cs)
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 {
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 	struct tm tm;
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-	time64_to_tm(ts->tv_sec,
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-		   (sbi->options.tz_set ? sbi->options.time_offset :
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-		   -sys_tz.tz_minuteswest) * SECS_PER_MIN, &tm);
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+	time64_to_tm(ts->tv_sec, -fat_tz_offset(sbi), &tm);
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 	/*  FAT can only support year between 1980 to 2107 */
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 	if (tm.tm_year < 1980 - 1900) {
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@@ -263,6 +267,88 @@
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 }
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 EXPORT_SYMBOL_GPL(fat_time_unix2fat);
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+static inline struct timespec64 fat_timespec64_trunc_2secs(struct timespec64 ts)
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+{
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+	return (struct timespec64){ ts.tv_sec & ~1ULL, 0 };
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+}
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+
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+static inline struct timespec64 fat_timespec64_trunc_10ms(struct timespec64 ts)
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+{
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+	if (ts.tv_nsec)
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+		ts.tv_nsec -= ts.tv_nsec % 10000000UL;
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+	return ts;
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+}
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+
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+/*
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+ * truncate the various times with appropriate granularity:
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+ *   root inode:
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+ *     all times always 0
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+ *   all other inodes:
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+ *     mtime - 2 seconds
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+ *     ctime
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+ *       msdos - 2 seconds
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+ *       vfat  - 10 milliseconds
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+ *     atime - 24 hours (00:00:00 in local timezone)
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+ */
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+int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
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+{
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+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
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+	struct timespec64 ts;
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+
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+	if (inode->i_ino == MSDOS_ROOT_INO)
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+		return 0;
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+
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+	if (now == NULL) {
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+		now = &ts;
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+		ts = current_time(inode);
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+	}
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+
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+	if (flags & S_ATIME) {
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+		/* to localtime */
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+		time64_t seconds = now->tv_sec - fat_tz_offset(sbi);
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+		s32 remainder;
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+
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+		div_s64_rem(seconds, SECS_PER_DAY, &remainder);
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+		/* to day boundary, and back to unix time */
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+		seconds = seconds + fat_tz_offset(sbi) - remainder;
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+
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+		inode->i_atime = (struct timespec64){ seconds, 0 };
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+	}
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+	if (flags & S_CTIME) {
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+		if (sbi->options.isvfat)
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+			inode->i_ctime = fat_timespec64_trunc_10ms(*now);
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+		else
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+			inode->i_ctime = fat_timespec64_trunc_2secs(*now);
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+	}
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+	if (flags & S_MTIME)
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+		inode->i_mtime = fat_timespec64_trunc_2secs(*now);
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+
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+	return 0;
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+}
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+EXPORT_SYMBOL_GPL(fat_truncate_time);
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+
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+int fat_update_time(struct inode *inode, struct timespec64 *now, int flags)
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+{
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+	int iflags = I_DIRTY_TIME;
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+	bool dirty = false;
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+
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+	if (inode->i_ino == MSDOS_ROOT_INO)
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+		return 0;
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+
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+	fat_truncate_time(inode, now, flags);
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+	if (flags & S_VERSION)
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+		dirty = inode_maybe_inc_iversion(inode, false);
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+	if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
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+	    !(inode->i_sb->s_flags & SB_LAZYTIME))
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+		dirty = true;
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+
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+	if (dirty)
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+		iflags |= I_DIRTY_SYNC;
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+	__mark_inode_dirty(inode, iflags);
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+	return 0;
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+}
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+EXPORT_SYMBOL_GPL(fat_update_time);
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+
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 int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
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 {
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 	int i, err = 0;