ceph: fix memory leak in ceph_direct_read_write()

In the Linux kernel, the following vulnerability has been resolved: ceph: fix memory leak in ceph_direct_read_write() The bvecs array which is allocated in iter_get_bvecs_alloc() is leaked and pages remain pinned if ceph_alloc_sparse_ext_map() fails. There is no need to delay the allocation of sparse_ext map until after the bvecs array is set up, so fix this by moving sparse_ext allocation a bit earlier. Also, make a similar adjustment in __ceph_sync_read() for consistency (a leak of the same kind in __ceph_sync_read() has been addressed differently).