fs:affs:Replace time_t with time64_t

The affs code uses "time_t" and "get_seconds()". This will cause
problems on 32-bit architectures in 2038 when time_t overflows.
This patch replaces them with "time64_t" and
"ktime_get_real_seconds()". This patch introduces expensive 64-bit
divsion in "secs_to_datestamp()", considering this function is not
called so often, the cost should be acceptable.

Reviewed-by: Arnd Bergmann <[email protected]>
Signed-off-by: DengChao <[email protected]>
Signed-off-by: Al Viro <[email protected]>

fs/affs/affs.h

@@ -138,7 +138,7 @@ extern int	affs_remove_hash(struct inode *dir, struct buffer_head *rem_bh);
 extern int	affs_remove_header(struct dentry *dentry);
 extern u32	affs_checksum_block(struct super_block *sb, struct buffer_head *bh);
 extern void	affs_fix_checksum(struct super_block *sb, struct buffer_head *bh);
-extern void	secs_to_datestamp(time_t secs, struct affs_date *ds);
+extern void	secs_to_datestamp(time64_t secs, struct affs_date *ds);
 extern umode_t	prot_to_mode(u32 prot);
 extern void	mode_to_prot(struct inode *inode);
 __printf(3, 4)

fs/affs/amigaffs.c

@@ -8,6 +8,7 @@
  *  Please send bug reports to: [email protected]
  */
 
+#include <linux/math64.h>
 #include "affs.h"
 
 /*
@@ -366,22 +367,22 @@ affs_fix_checksum(struct super_block *sb, struct buffer_head *bh)
 }
 
 void
-secs_to_datestamp(time_t secs, struct affs_date *ds)
+secs_to_datestamp(time64_t secs, struct affs_date *ds)
 {
 	u32	 days;
 	u32	 minute;
+	s32	 rem;
 
 	secs -= sys_tz.tz_minuteswest * 60 + ((8 * 365 + 2) * 24 * 60 * 60);
 	if (secs < 0)
 		secs = 0;
-	days    = secs / 86400;
-	secs   -= days * 86400;
-	minute  = secs / 60;
-	secs   -= minute * 60;
+	days    = div_s64_rem(secs, 86400, &rem);
+	minute  = rem / 60;
+	rem    -= minute * 60;
 
 	ds->days = cpu_to_be32(days);
 	ds->mins = cpu_to_be32(minute);
-	ds->ticks = cpu_to_be32(secs * 50);
+	ds->ticks = cpu_to_be32(rem * 50);
 }
 
 umode_t

fs/affs/super.c

@@ -32,7 +32,7 @@ affs_commit_super(struct super_block *sb, int wait)
 	struct affs_root_tail *tail = AFFS_ROOT_TAIL(sb, bh);
 
 	lock_buffer(bh);
-	secs_to_datestamp(get_seconds(), &tail->disk_change);
+	secs_to_datestamp(ktime_get_real_seconds(), &tail->disk_change);
 	affs_fix_checksum(sb, bh);
 	unlock_buffer(bh);