Linux 4.18 compat: inode timespec -> timespec64

Commit torvalds/linux@95582b0 changes the inode i_atime, i_mtime,
and i_ctime members form timespec's to timespec64's to make them
2038 safe.  As part of this change the current_time() function was
also updated to return the timespec64 type.

Resolve this issue by introducing a new inode_timespec_t type which
is defined to match the timespec type used by the inode.  It should
be used when working with inode timestamps to ensure matching types.

The timestruc_t type under Illumos was used in a similar fashion but
was specified to always be a timespec_t.  Rather than incorrectly
define this type all timespec_t types have been replaced by the new
inode_timespec_t type.

Finally, the kernel and user space 'sys/time.h' headers were aligned
with each other.  They define as appropriate for the context several
constants as macros and include static inline implementation of
gethrestime(), gethrestime_sec(), and gethrtime().

Reviewed-by: Chunwei Chen <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #7643 

1 files changed, 25 insertions, 8 deletions

diff --git a/include/sys/zfs_znode.h b/include/sys/zfs_znode.h
index 3f2bd1fbb..a34d24532 100644
--- a/include/sys/zfs_znode.h
+++ b/include/sys/zfs_znode.h
@@ -291,19 +291,36 @@ zfs_inherit_projid(znode_t *dzp)
 
 extern unsigned int zfs_object_mutex_size;
 
-/* Encode ZFS stored time values from a struct timespec */
+/*
+ * Encode ZFS stored time values from a struct timespec / struct timespec64.
+ */
 #define	ZFS_TIME_ENCODE(tp, stmp)		\
-{						\
+do {						\
 	(stmp)[0] = (uint64_t)(tp)->tv_sec;	\
 	(stmp)[1] = (uint64_t)(tp)->tv_nsec;	\
-}
+} while (0)
 
-/* Decode ZFS stored time values to a struct timespec */
+#if defined(HAVE_INODE_TIMESPEC64_TIMES)
+/*
+ * Decode ZFS stored time values to a struct timespec64
+ * 4.18 and newer kernels.
+ */
 #define	ZFS_TIME_DECODE(tp, stmp)		\
-{						\
-	(tp)->tv_sec = (time_t)(stmp)[0];		\
-	(tp)->tv_nsec = (long)(stmp)[1];		\
-}
+do {						\
+	(tp)->tv_sec = (time64_t)(stmp)[0];	\
+	(tp)->tv_nsec = (long)(stmp)[1];	\
+} while (0)
+#else
+/*
+ * Decode ZFS stored time values to a struct timespec
+ * 4.17 and older kernels.
+ */
+#define	ZFS_TIME_DECODE(tp, stmp)		\
+do {						\
+	(tp)->tv_sec = (time_t)(stmp)[0];	\
+	(tp)->tv_nsec = (long)(stmp)[1];	\
+} while (0)
+#endif /* HAVE_INODE_TIMESPEC64_TIMES */
 
 /*
  * Timestamp defines