linux-kernel - [PATCH] [RESEND] sysvfs: use ktime_get_real

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Date:   Fri, 13 Jul 2018 16:52:28 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     y2038@...ts.linaro.org, linux-fsdevel@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Christoph Hellwig <hch@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Howells <dhowells@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] [RESEND] sysvfs: use ktime_get_real_seconds() for superblock stamp

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@...utronix.de>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Originally sent on Jun 19, got an Ack but no other reply.

Christoph apparently hasn't applied any sysvfs patches in many years,
so I'd like someone else to take this one.

Al or Andrew, could you take this patch for 4.19 as well?
---
 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 47f66bbc4578..e8927ea70d12 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