add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/fs/fat/fat.h
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@@ -142,6 +142,34 @@
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 	return sb->s_fs_info;
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 }
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+/*
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+ * Functions that determine the variant of the FAT file system (i.e.,
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+ * whether this is FAT12, FAT16 or FAT32.
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+ */
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+static inline bool is_fat12(const struct msdos_sb_info *sbi)
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+{
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+	return sbi->fat_bits == 12;
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+}
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+
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+static inline bool is_fat16(const struct msdos_sb_info *sbi)
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+{
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+	return sbi->fat_bits == 16;
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+}
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+
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+static inline bool is_fat32(const struct msdos_sb_info *sbi)
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+{
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+	return sbi->fat_bits == 32;
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+}
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+
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+/* Maximum number of clusters */
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+static inline u32 max_fat(struct super_block *sb)
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+{
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+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
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+
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+	return is_fat32(sbi) ? MAX_FAT32 :
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+		is_fat16(sbi) ? MAX_FAT16 : MAX_FAT12;
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+}
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+
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 static inline struct msdos_inode_info *MSDOS_I(struct inode *inode)
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 {
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 	return container_of(inode, struct msdos_inode_info, vfs_inode);
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@@ -257,7 +285,7 @@
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 				const struct msdos_dir_entry *de)
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 {
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 	int cluster = le16_to_cpu(de->start);
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-	if (sbi->fat_bits == 32)
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+	if (is_fat32(sbi))
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 		cluster |= (le16_to_cpu(de->starthi) << 16);
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 	return cluster;
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 }
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@@ -416,6 +444,10 @@
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 			      __le16 __time, __le16 __date, u8 time_cs);
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 extern void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
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 			      __le16 *time, __le16 *date, u8 *time_cs);
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+extern int fat_truncate_time(struct inode *inode, struct timespec64 *now,
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+			     int flags);
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+extern int fat_update_time(struct inode *inode, struct timespec64 *now,
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+			   int flags);
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 extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
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 int fat_cache_init(void);