Le 08/05/2022 à 15:09, Baolin Wang a écrit : > > > On 5/8/2022 7:09 PM, Muchun Song wrote: >> On Sun, May 08, 2022 at 05:36:39PM +0800, Baolin Wang wrote: >>> It is incorrect to use ptep_clear_flush() to nuke a hugetlb page >>> table when unmapping or migrating a hugetlb page, and will change >>> to use huge_ptep_clear_flush() instead in the following patches. >>> >>> So this is a preparation patch, which changes the >>> huge_ptep_clear_flush() >>> to return the original pte to help to nuke a hugetlb page table. >>> >>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> >>> Acked-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> >> >> Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> > > Thanks for reviewing. > >> >> But one nit below: >> >> [...] >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>> index 8605d7e..61a21af 100644 >>> --- a/mm/hugetlb.c >>> +++ b/mm/hugetlb.c >>> @@ -5342,7 +5342,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct >>> *mm, struct vm_area_struct *vma, >>> ClearHPageRestoreReserve(new_page); >>> /* Break COW or unshare */ >>> - huge_ptep_clear_flush(vma, haddr, ptep); >>> + (void)huge_ptep_clear_flush(vma, haddr, ptep); >> >> Why add a "(void)" here? Is there any warning if no "(void)"? >> IIUC, I think we can remove this, right? > > I did not meet any warning without the casting, but this is per Mike's > comment[1] to make the code consistent with other functions casting to > void type explicitly in hugetlb.c file. > > [1] > https://lore.kernel.org/all/495c4ebe-a5b4-afb6-4cb0-956c1b18d0cc@xxxxxxxxxx/ > As far as I understand, Mike said that you should be accompagnied with a big fat comment explaining why we ignore the returned value from huge_ptep_clear_flush(). By the way huge_ptep_clear_flush() is not declared 'must_check' so this cast is just visual polution and should be removed. In the meantime the comment suggested by Mike should be added instead. Christophe
