jbd2_alloc
tmp = jbd2_alloc(bh_in->b_size, GFP_NOFS | __GFP_NOFAIL);
frozen_buffer = jbd2_alloc(jh2bh(jh)->b_size,
committed_data = jbd2_alloc(jh2bh(jh)->b_size,
extern void *jbd2_alloc(size_t size, gfp_t flags);