Hi, The following patch is an attempt to make huge_pte_offset() consistent when dealing with different levels of the page table and document the expected semantics. Previously posting can be found at [0]. Changelog RFC - v1 * Merge Patch 1 and 2 - preserve bisectability * Drop RFC tag Original cover letter follows... The generic implementation of huge_pte_offset() has inconsistent behaviour when looking up hugepage PUDs vs PMDs entries that are not present (returning NULL vs pte_t*). Similarly, it returns NULL when encountering swap entries although all the callers have special checks to properly deal with swap entries. Without clear semantics, it is difficult to determine if a change breaks huge_pte_offset() without going through all the scenarios where it is used. I faced this recently when updating the arm64 implementation of huge_pte_offset() to handle swap entries (related to enabling poisoned memeory)[1]. And will come across again when I update it for contiguous hugepage support now that core changes have been merged. To address these issues, this following patch - * makes huge_pte_offset() consistent between PUD and PMDs * and, documents the expected behaviour of huge_pte_offset() All feedback welcome. Thanks, Punit [0] https://lkml.org/lkml/2017/7/24/514 [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f02ab08afbe76ee7b0b2a34a9970e7dd200d8b01 Punit Agrawal (1): mm/hugetlb: Make huge_pte_offset() consistent and document behaviour mm/hugetlb.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) -- 2.11.0
