On Thu, Nov 13, 2014 at 03:50:02PM -0800, Linus Torvalds wrote: > +/* > + * The 'tree_level' data only describes one particular level > + * of the tree. The upper levels are totally invisible to the > + * user of the tree walker, since the tree walker will walk > + * those using the tree definitions. > + * > + * NOTE! "struct tree_entry" is an opaque type, and is just a > + * used as a pointer to the particular level. You can figure > + * out which level you are at by looking at the "tree_level", > + * but even better is to just use different "lookup()" > + * functions for different levels, at which point the > + * function is inherent to the level. Please, don't. We will end up with the same last-level centric code as we have now in mm subsystem: all code only cares about pte. It makes implementing variable page size support really hard and lead to copy-paste approach. And to hugetlb parallel world... It would be nice to have tree_level description generic enough to get rid of pte_present()/pte_dirty()/pte_* and implement generic helpers instead. Apart from variable page size problem, we could get one day support different CPU page table format supported in runtime: PAE/non-PAE on 32-bit x86 or LPAE/non-LPAE on ARM in one binary kernel image. The big topic is how to get it done without significant runtime cost :-/ -- Kirill A. Shutemov -- 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>