On Thu, 1 Feb 2018, Igor Stoppa wrote: > > Would it not be better to use compound page allocations here? > > page_head(whatever) gets you the head page where you can store all sorts > > of information about the chunk of memory. > > Can you please point me to this function/macro? I don't seem to be able > to find it, at least not in 4.15
Ok its compound_head(). See also the use in the SLAB and SLUB allocator. > During hardened user copy permission check, I need to confirm if the > memory range that would be exposed to userspace is a legitimate > sub-range of a pmalloc allocation. If you save the size in the head page struct then you could do that pretty fast. > I cannot comment on your proposal because I do not know where to find > the reference you made, or maybe I do not understand what you mean :-( compund pages are higher order pages that are handled as a single page by the VM. See https://lwn.net/Articles/619514/
