On 03/20/2015 10:31 PM, Matthew Wilcox wrote: <> > > There's a lot of code out there that relies on struct page being PAGE_SIZE > bytes. Not so much really. Not at the lower end of the stack. You can actually feed a vp = kmalloc(64K); bv_page = virt_to_page(vp) bv_len = 64k And feed that to an hard drive. It works. The only last stronghold of PAGE_SIZE is at the page-cache and page-fault granularity where the minimum is the better. But it should not be hard to clean up the lower end of the stack. Even introduce a: page_size(page) You will find that every subsystem that can work with a sub-page size similar to above bv_len. Will also work well with bigger than PAGE_SIZE bv_len equivalent. Only the BUG_ONs need to convert to page_size(page) instead of PAGE_SIZE > I'm cool with replacing 'struct page' with 'struct superpage' > [1] in the biovec and auditing all of the code which touches it ... but > that's going to be a lot of code! I'm not sure it's less code than > going directly to 'just do I/O on PFNs'. > struct page already knows how to be a super-page. with the THP mechanics. All a page_size(page) needs is a call to its section, we do not need any added storage at page-struct. (And we can cache this as a flag we actually already have a flag) It looks like you are very trigger happy to change "biovec and auditing all of the code which touches it" I believe long long term your #1b is the correct "full audit" path: Page Is the virtual-2-page-2-physical descriptor + state. It is variable size > [1] Please, somebody come up with a better name! sure struct page *page. The one to kill is PAGE_SIZE. In most current code it can just be MIN_PAGE_SIZE and CACHE_PAGE_SIZE == MIN_PAGE_SIZE. Only novelty is enhance of the split_huge_page in the case of "page-fault-granularity". Thanks Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
