> > Likewise. > >> + f_off = f->page_offset; >> + f_size = f->size; >> + >> + vaddr = kmap_atomic(skb_frag_page(f)); > > I looked at some kmap_atomic() implementations and I do not think > it supports compound pages.
Indeed. Thanks. It appears that I can do the obvious thing and kmap the individual page that is being copied inside the loop: kmap_atomic(skb_frag_page(f) + (f_off >> PAGE_SHIFT)); This is similar to existing logic in copy_huge_page_from_user and __flush_dcache_page in arch/arm/mm/flush.c But, this also applies to other skb operations that call kmap_atomic, such as skb_copy_bits and __skb_checksum. Not all can be called from a codepath with a compound user page, but I have to address the ones that can.
