fs: ceph: CURRENT_TIME with ktime_get_real_ts()

CURRENT_TIME is not y2038 safe.  The macro will be deleted and all the
references to it will be replaced by ktime_get_* apis.

struct timespec is also not y2038 safe.  Retain timespec for timestamp
representation here as ceph uses it internally everywhere.  These
references will be changed to use struct timespec64 in a separate patch.

The current_fs_time() api is being changed to use vfs struct inode* as
an argument instead of struct super_block*.

Set the new mds client request r_stamp field using ktime_get_real_ts()
instead of using current_fs_time().

Also, since r_stamp is used as mtime on the server, use timespec_trunc()
to truncate the timestamp, using the right granularity from the
superblock.

This api will be transitioned to be y2038 safe along with vfs.

Link: http://lkml.kernel.org/r/1491613030-11599-5-git-send-email-deepa.kernel@gmail.com


Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
M:	Ilya Dryomov <idryomov@gmail.com>
M:	"Yan, Zheng" <zyan@redhat.com>
M:	Sage Weil <sage@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>