Check that a page_frag contains enough room
bool skb_page_frag_refill(unsigned int sz, struct page_frag * pfrag, gfp_t prio);
sz
minimum size of the fragment we want to get
pfrag
pointer to page_frag
prio
priority for memory allocation
While this allocator tries to use high order pages, there is no guarantee that allocations succeed. Therefore, sz MUST be less or equal than PAGE_SIZE.