On 01/02/18 02:00, Christopher Lameter wrote: > On Tue, 30 Jan 2018, Igor Stoppa wrote: > >> @@ -1769,6 +1774,9 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, >> >> kmemleak_vmalloc(area, size, gfp_mask); >> >> + for (page_counter = 0; page_counter < area->nr_pages; page_counter++) >> + area->pages[page_counter]->area = area; >> + >> return addr; > > Well this introduces significant overhead for large sized allocation. Does > this not matter because the areas are small? Relatively significant? I do not object to your comment, but in practice i see that: - vmalloc is used relatively little - allocations do not seem to be huge - there seem to be way larger overheads in the handling of virtual pages (see my proposal for the LFS/m summit, about collapsing struct vm_struct and struct vmap_area) > 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 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. So, I start with the pair (address, size) and I must end up to something I can compare it against. The idea here is to pass through struct_page and then the related vm_struct/vmap_area, which already has the information about the specific chunk of virtual memory. 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 :-( -- igor -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
