On 07/13/22 15:46, Axel Rasmussen wrote:
> I think there is a small mistake in this patch.
>
> Consider the non-minor-fault case. We have this block:
>
> /* Add shared, newly allocated pages to the page cache. */
> if (vm_shared && !is_continue) {
> /* ... */
> }
>
> In here, we've added the newly allocated page to the page cache, and
> we've set this page_in_pagecache flag to true. But we *do not* setup
> rmap for this page in this block. I think in this case, the patch will
> cause us to do the wrong thing: we should hugepage_add_new_anon_rmap()
> further down, but with this patch we dup instead.
I am not sure I follow. The patch from Miaohe Lin would not change any
behavior in the 'if (vm_shared && !is_continue)' case. In this case
both vm_shared and page_in_pagecache are true.
IIUC, the patch would address the case where !vm_shared && is_continue.
On 07/12/22 21:05, Miaohe Lin wrote:
> In MCOPY_ATOMIC_CONTINUE case with a non-shared VMA, pages in the page
> cache are installed in the ptes. But hugepage_add_new_anon_rmap is called
> for them mistakenly because they're not vm_shared. This will corrupt the
> page->mapping used by page cache code.
>
> Fixes: f619147104c8 ("userfaultfd: add UFFDIO_CONTINUE ioctl")
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/hugetlb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 8d379e03f672..b232e1508e49 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6038,7 +6038,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
> if (!huge_pte_none_mostly(huge_ptep_get(dst_pte)))
> goto out_release_unlock;
>
> - if (vm_shared) {
> + if (page_in_pagecache) {
> page_dup_file_rmap(page, true);
> } else {
> ClearHPageRestoreReserve(page);
--
Mike Kravetz
