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/[email protected]
Signed-off-by: Deepa Dinamani <[email protected]>
Reviewed-by: Arnd Bergmann <[email protected]>
M:	Ilya Dryomov <[email protected]>
M:	"Yan, Zheng" <[email protected]>
M:	Sage Weil <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/block/rbd.c

@@ -1922,7 +1922,7 @@ static void rbd_osd_req_format_write(struct rbd_obj_request *obj_request)
 {
 	struct ceph_osd_request *osd_req = obj_request->osd_req;
 
-	osd_req->r_mtime = CURRENT_TIME;
+	ktime_get_real_ts(&osd_req->r_mtime);
 	osd_req->r_data_offset = obj_request->offset;
 }