fs: add timespec64_truncate()

As vfs moves to using struct timespec64 to represent times,
update the argument to timespec_truncate() to use
struct timespec64. Also change the name of the function.
The rest of the implementation logic is the same.

Move this to fs/inode.c instead of kernel/time/time.c as all the
users of this api are filesystems.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: <viro@zeniv.linux.org.uk>

1 files changed, 24 insertions, 0 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 13ceb98c3bd3..93af998ee290 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2111,6 +2111,30 @@ void inode_nohighmem(struct inode *inode)
 EXPORT_SYMBOL(inode_nohighmem);
 
 /**
+ * timespec64_trunc - Truncate timespec64 to a granularity
+ * @t: Timespec64
+ * @gran: Granularity in ns.
+ *
+ * Truncate a timespec64 to a granularity. Always rounds down. gran must
+ * not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
+ */
+struct timespec64 timespec64_trunc(struct timespec64 t, unsigned gran)
+{
+	/* Avoid division in the common cases 1 ns and 1 s. */
+	if (gran == 1) {
+		/* nothing */
+	} else if (gran == NSEC_PER_SEC) {
+		t.tv_nsec = 0;
+	} else if (gran > 1 && gran < NSEC_PER_SEC) {
+		t.tv_nsec -= t.tv_nsec % gran;
+	} else {
+		WARN(1, "illegal file time granularity: %u", gran);
+	}
+	return t;
+}
+EXPORT_SYMBOL(timespec64_trunc);
+
+/**
  * current_time - Return FS time
  * @inode: inode.
  *