ceph: Add check returned value on func ceph_calc_ceph_pg.

Func ceph_calc_ceph_pg maybe failed.So add check for returned value.
Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Sage Weil <sage@inktank.com>

fs/ceph/ioctl.c

@@ -211,8 +211,12 @@ static long ceph_ioctl_get_dataloc(struct file *file, void __user *arg)
 	snprintf(dl.object_name, sizeof(dl.object_name), "%llx.%08llx",
 		 ceph_ino(inode), dl.object_no);
 
-	ceph_calc_ceph_pg(&pgid, dl.object_name, osdc->osdmap,
+	r = ceph_calc_ceph_pg(&pgid, dl.object_name, osdc->osdmap,
 				ceph_file_layout_pg_pool(ci->i_layout));
+	if (r < 0) {
+		up_read(&osdc->map_sem);
+		return r;
+	}
 
 	dl.osd = ceph_calc_pg_primary(osdc->osdmap, pgid);
 	if (dl.osd >= 0) {