Messages in this thread | | | Subject | Re: [PATCH 08/17] prmem: struct page: track vmap_area | From | Igor Stoppa <> | Date | Mon, 29 Oct 2018 20:21:18 +0200 |
| |
On 25/10/2018 03:13, Matthew Wilcox wrote: > On Thu, Oct 25, 2018 at 02:01:02AM +0300, Igor Stoppa wrote: >>>> @@ -1747,6 +1750,10 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align, >>>> if (!addr) >>>> return NULL; >>>> + va = __find_vmap_area((unsigned long)addr); >>>> + for (i = 0; i < va->vm->nr_pages; i++) >>>> + va->vm->pages[i]->area = va; >>> >>> I don't like it that you're calling this for _every_ vmalloc() caller >>> when most of them will never use this. Perhaps have page->va be initially >>> NULL and then cache the lookup in it when it's accessed for the first time. >>> >> >> If __find_vmap_area() was part of the API, this loop could be left out from >> __vmalloc_node_range() and the user of the allocation could initialize the >> field, if needed. >> >> What is the reason for keeping __find_vmap_area() private? > > Well, for one, you're walking the rbtree without holding the spinlock, > so you're going to get crashes. I don't see why we shouldn't export > find_vmap_area() though.
Argh, yes, sorry. But find_vmap_area() would be enough for what I need.
> Another way we could approach this is to embed the vmap_area in the > vm_struct. It'd require a bit of juggling of the alloc/free paths in > vmalloc, but it might be worthwhile.
I have a feeling of unease about the whole vmap_area / vm_struct duality. They clearly are different types, with different purposes, but here and there there are functions that are named after some "area", yet they actually refer to vm_struct pointers.
I wouldn't mind spending some time understanding the reason for this apparently bizarre choice, but after I have emerged from the prmem swamp.
For now I'd stick to find_vmap_area().
-- igor
| |