Re: [PATCH] Revert "mm/page_isolation: unset migratetype directly for non Buddy page"

[Chen Wandun]

在 2022/1/17 23:32, David Hildenbrand 写道:
> On 17.01.22 15:27, Chen Wandun wrote:
> > This reverts commit 075782149abff45ee22f27315eced44d02b96779.
> >
> > commit 075782149abf ("mm/page_isolation: unset migratetype directly for
> > non Buddy page") will result memory that should in buddy disappear by
> > mistake. move_freepages_block move all pages in pageblock instead of
> > pages indicated by input parameter, so if input pages is not in buddy
> > but other pages in pageblock is in buddy, it will result in page out of
> > control.
> I was wondering about exactly that condition when skimming over the
> patch but didn't have time review in detail.
when the first valid page in pageblock is non-buddy page and the page order
is not equal pagblock_order,  unset_migratetype_isolate will missing 
move free
page in this pageblock.
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>
>
> > Reported-by: "kernelci.org bot" <bot@xxxxxxxxxxxx>
> > Signed-off-by: Chen Wandun <chenwandun@xxxxxxxxxx>
> > ---
> >   mm/page_isolation.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> > index 6a0ddda6b3c5..f67c4c70f17f 100644
> > --- a/mm/page_isolation.c
> > +++ b/mm/page_isolation.c
> > @@ -115,7 +115,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
> >   	 * onlining - just onlined memory won't immediately be considered for
> >   	 * allocation.
> >   	 */
> > -	if (!isolated_page && PageBuddy(page)) {
> > +	if (!isolated_page) {
> >   		nr_pages = move_freepages_block(zone, page, migratetype, NULL);
> >   		__mod_zone_freepage_state(zone, nr_pages, migratetype);
> >   	}