On 2022/7/30 2:11, Mike Kravetz wrote: > On 07/29/22 10:02, Miaohe Lin wrote: >> On 2022/7/7 4:23, Mike Kravetz wrote: >>> Create the new routine hugetlb_unmap_file_folio that will unmap a single >>> file folio. This is refactored code from hugetlb_vmdelete_list. It is >>> modified to do locking within the routine itself and check whether the >>> page is mapped within a specific vma before unmapping. >>> >>> This refactoring will be put to use and expanded upon in a subsequent >>> patch adding vma specific locking. >>> >>> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> >>> --- >>> fs/hugetlbfs/inode.c | 124 +++++++++++++++++++++++++++++++++---------- >>> 1 file changed, 95 insertions(+), 29 deletions(-) >>> >>> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c >>> index 31bd4325fce5..0eac0ea2a245 100644 >>> --- a/fs/hugetlbfs/inode.c >>> +++ b/fs/hugetlbfs/inode.c >>> @@ -396,6 +396,94 @@ static int hugetlbfs_write_end(struct file *file, struct address_space *mapping, >>> return -EINVAL; >>> } >>> >>> +/* >>> + * Called with i_mmap_rwsem held for inode based vma maps. This makes >>> + * sure vma (and vm_mm) will not go away. We also hold the hugetlb fault >>> + * mutex for the page in the mapping. So, we can not race with page being >>> + * faulted into the vma. >>> + */ >>> +static bool hugetlb_vma_maps_page(struct vm_area_struct *vma, >>> + unsigned long addr, struct page *page) >>> +{ >>> + pte_t *ptep, pte; >>> + >>> + ptep = huge_pte_offset(vma->vm_mm, addr, >>> + huge_page_size(hstate_vma(vma))); >>> + >>> + if (!ptep) >>> + return false; >>> + >>> + pte = huge_ptep_get(ptep); >>> + if (huge_pte_none(pte) || !pte_present(pte)) >>> + return false; >>> + >>> + if (pte_page(pte) == page) >>> + return true; >>> + >>> + return false; /* WTH??? */ >> >> I'm sorry but what does WTH means? IIUC, this could happen if pte_page is a COW-ed private page? >> vma_interval_tree_foreach doesn't exclude the private mapping even after cow? > > My apologies, I left that comment in during development and should have removed > it. WTH is an acronym for 'What the Heck?". I added it because I did not > think we should ever get to this return statement. > That's all right. Thanks for your hard work. > I am not sure if your COW of a private page would get us to this return > statement. In any case, if we get there we need to return false. > > Thank you for your analysis and comments! >