staging/lustre/llite: glimpse the inode before doing fiemap

For a new inode, the i_size is 0 until a stat, which will yield
an empty fiemap result.
Fix the issue by glimpsing the size before doing fiemap.
Signed-off-by: Li Dongyang <dongyang.li@anu.edu.au>
Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: http://review.whamcloud.com/13439
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6091Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/file.c

@@ -1712,6 +1712,12 @@ static int ll_do_fiemap(struct inode *inode, struct ll_user_fiemap *fiemap,
 	fm_key.oa.o_oi = lsm->lsm_oi;
 	fm_key.oa.o_valid = OBD_MD_FLID | OBD_MD_FLGROUP;
 
+	if (i_size_read(inode) == 0) {
+		rc = ll_glimpse_size(inode);
+		if (rc)
+			goto out;
+	}
+
 	obdo_from_inode(&fm_key.oa, inode, OBD_MD_FLSIZE);
 	obdo_set_parent_fid(&fm_key.oa, &ll_i2info(inode)->lli_fid);
 	/* If filesize is 0, then there would be no objects for mapping */