On Fri, Feb 15, 2019 at 02:08:26PM -0800, Zi Yan wrote: > +struct page_flags { > + unsigned int page_error :1; > + unsigned int page_referenced:1; > + unsigned int page_uptodate:1; > + unsigned int page_active:1; > + unsigned int page_unevictable:1; > + unsigned int page_checked:1; > + unsigned int page_mappedtodisk:1; > + unsigned int page_dirty:1; > + unsigned int page_is_young:1; > + unsigned int page_is_idle:1; > + unsigned int page_swapcache:1; > + unsigned int page_writeback:1; > + unsigned int page_private:1; > + unsigned int __pad:3; > +};
I'm not sure how to feel about this. It's a bit fragile versus somebody adding new page flags. I don't know whether it's needed or whether you can just copy page->flags directly because you're holding PageLock. > +static void exchange_page(char *to, char *from) > +{ > + u64 tmp; > + int i; > + > + for (i = 0; i < PAGE_SIZE; i += sizeof(tmp)) { > + tmp = *((u64 *)(from + i)); > + *((u64 *)(from + i)) = *((u64 *)(to + i)); > + *((u64 *)(to + i)) = tmp; > + } > +} I have a suspicion you'd be better off allocating a temporary page and using copy_page(). Some architectures have put a lot of effort into making copy_page() run faster. > + xa_lock_irq(&to_mapping->i_pages); > + > + to_pslot = radix_tree_lookup_slot(&to_mapping->i_pages, > + page_index(to_page)); This needs to be converted to the XArray. radix_tree_lookup_slot() is going away soon. You probably need: XA_STATE(to_xas, &to_mapping->i_pages, page_index(to_page)); This is a lot of code and I'm still trying to get my head aroud it all. Thanks for putting in this work; it's good to see this approach being explored.