On Mon, Sep 05, 2022 at 02:53:41PM +0800, Miaohe Lin wrote:
> On 2022/9/5 13:22, HORIGUCHI NAOYA(堀口 直也) wrote:
> > Hi Miaohe,
> >
> > On Tue, Aug 30, 2022 at 08:36:00PM +0800, Miaohe Lin wrote:
> >> It's more recommended to use __PageMovable() to detect non-lru movable
> >> pages. We can avoid bumping page refcnt via isolate_movable_page() for
> >> the isolated lru pages. Also if pages become PageLRU just after they're
> >> checked but before trying to isolate them, isolate_lru_page() will be
> >> called to do the right work.
> >
> > Good point, non-lru movable page is currently handled by isolate_lru_page(),
> > which always fails. This means that we lost the chance of soft-offlining
> > for any non-lru movable page. So this patch improves the situation.
>
> Non-lru movable page will still be handled by isolate_movable_page() before the code change
> as they don't have PageLRU set. The current situation is that the isolated LRU pages are
> passed to isolate_movable_page() uncorrectly. This might not hurt. But the chance that pages
> become un-isolated and thus available just after checking could be seized with this patch.
OK, thank you for correct me.
>
> >
> >>
> >> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> >> ---
> >> mm/memory-failure.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> >> index a923a6dde871..3966fa6abe03 100644
> >> --- a/mm/memory-failure.c
> >> +++ b/mm/memory-failure.c
> >> @@ -2404,7 +2404,7 @@ EXPORT_SYMBOL(unpoison_memory);
> >> static bool isolate_page(struct page *page, struct list_head *pagelist)
> >> {
> >> bool isolated = false;
> >> - bool lru = PageLRU(page);
> >> + bool lru = !__PageMovable(page);
> >
> > It seems that PAGE_MAPPING_MOVABLE is not set for hugetlb pages, so
> > lru becomes true for them. Then, if isolate_hugetlb() succeeds,
> > inc_node_page_state() is called for hugetlb pages, maybe that's not expected.
>
> Yes, that's unexpected. Thanks for pointing this out.
>
> >
> >>
> >> if (PageHuge(page)) {
> >> isolated = !isolate_hugetlb(page, pagelist);
> > } else {
> > if (lru)
> > isolated = !isolate_lru_page(page);
> > else
> > isolated = !isolate_movable_page(page, ISOLATE_UNEVICTABLE);
> >
> > if (isolated)
> > list_add(&page->lru, pagelist);
> > }
> >
> > if (isolated && lru)
> > inc_node_page_state(page, NR_ISOLATED_ANON +
> > page_is_file_lru(page));
> >
> > so, how about moving this if block into the above else block?
> > Then, the automatic variable lru can be moved into the else block.
>
> Do you mean something like below?
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index df3bf266eebf..48780f3a61d3 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2404,24 +2404,25 @@ EXPORT_SYMBOL(unpoison_memory);
> static bool isolate_page(struct page *page, struct list_head *pagelist)
> {
> bool isolated = false;
> - bool lru = !__PageMovable(page);
>
> if (PageHuge(page)) {
> isolated = !isolate_hugetlb(page, pagelist);
> } else {
> + bool lru = !__PageMovable(page);
> +
> if (lru)
> isolated = !isolate_lru_page(page);
> else
> isolated = !isolate_movable_page(page, ISOLATE_UNEVICTABLE);
>
> - if (isolated)
> + if (isolated) {
> list_add(&page->lru, pagelist);
> + if (lru)
> + inc_node_page_state(page, NR_ISOLATED_ANON +
> + page_is_file_lru(page));
> + }
> }
>
> - if (isolated && lru)
> - inc_node_page_state(page, NR_ISOLATED_ANON +
> - page_is_file_lru(page));
> -
> /*
> * If we succeed to isolate the page, we grabbed another refcount on
> * the page, so we can safely drop the one we got from get_any_pages().
>
Yes, that's exactly what I thought of.
Thanks,
Naoya Horiguchi
