[PATCH] sysvfs: use ktime_get_real_seconds() for superblock stamp

[PATCH] sysvfs: use ktime_get_real_seconds() for superblock stamp

[Arnd Bergmann]

get_seconds() is deprecated in favor of ktime_get_real_seconds(),
which returns a 64-bit timestamp.

In the SYSV file system, the superblock timestamp is only 32 bits
wide, and it is used to check whether a file system is clean, so
the best solution seems to be to force a wraparound and explicitly
convert it to an unsigned 32-bit value.

This is independent of the inode timestamps that are also 32-bit
wide on disk and that come from current_time().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 fs/sysv/inode.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/sysv/inode.c b/fs/sysv/inode.c
index bec9f79adb25..499a20a5a010 100644
--- a/fs/sysv/inode.c
+++ b/fs/sysv/inode.c
@@ -35,7 +35,7 @@
 static int sysv_sync_fs(struct super_block *sb, int wait)
 {
 	struct sysv_sb_info *sbi = SYSV_SB(sb);
-	unsigned long time = get_seconds(), old_time;
+	u32 time = (u32)ktime_get_real_seconds(), old_time;
 
 	mutex_lock(&sbi->s_lock);
 
@@ -46,8 +46,8 @@ static int sysv_sync_fs(struct super_block *sb, int wait)
 	 */
 	old_time = fs32_to_cpu(sbi, *sbi->s_sb_time);
 	if (sbi->s_type == FSTYPE_SYSV4) {
-		if (*sbi->s_sb_state == cpu_to_fs32(sbi, 0x7c269d38 - old_time))
-			*sbi->s_sb_state = cpu_to_fs32(sbi, 0x7c269d38 - time);
+		if (*sbi->s_sb_state == cpu_to_fs32(sbi, 0x7c269d38u - old_time))
+			*sbi->s_sb_state = cpu_to_fs32(sbi, 0x7c269d38u - time);
 		*sbi->s_sb_time = cpu_to_fs32(sbi, time);
 		mark_buffer_dirty(sbi->s_bh2);
 	}
-- 
2.9.0

Re: [PATCH] sysvfs: use ktime_get_real_seconds() for superblock stamp

[Thomas Gleixner]

On Tue, 19 Jun 2018, Arnd Bergmann wrote:

> get_seconds() is deprecated in favor of ktime_get_real_seconds(),
> which returns a 64-bit timestamp.
> 
> In the SYSV file system, the superblock timestamp is only 32 bits
> wide, and it is used to check whether a file system is clean, so
> the best solution seems to be to force a wraparound and explicitly
> convert it to an unsigned 32-bit value.
> 
> This is independent of the inode timestamps that are also 32-bit
> wide on disk and that come from current_time().

Acked-by: Thomas Gleixner <tglx@linutronix.de>