On Wed 26-07-17 10:50:38, Michal Hocko wrote: > On Tue 25-07-17 16:41:14, Punit Agrawal wrote: > > When walking the page tables to resolve an address that points to > > !p*d_present() entry, huge_pte_offset() returns inconsistent values > > depending on the level of page table (PUD or PMD). > > > > It returns NULL in the case of a PUD entry while in the case of a PMD > > entry, it returns a pointer to the page table entry. > > > > A similar inconsitency exists when handling swap entries - returns NULL > > for a PUD entry while a pointer to the pte_t is retured for the PMD > > entry. > > > > Update huge_pte_offset() to make the behaviour consistent - return NULL > > in the case of p*d_none() and a pointer to the pte_t for hugepage or > > swap entries. > > > > Document the behaviour to clarify the expected behaviour of this > > function. This is to set clear semantics for architecture specific > > implementations of huge_pte_offset(). > > hugetlb pte semantic is a disaster and I agree it could see some > cleanup/clarifications but I am quite nervous to see a patchi like this. > How do we check that nothing will get silently broken by this change? Forgot to add. Hugetlb have been special because of the pte sharing. I haven't looked into that code for quite some time but there might be a good reason why pud behave differently. -- Michal Hocko SUSE Labs -- 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>
