On Mon 13-09-21 19:51:25, Miaohe Lin wrote:
> In start_isolate_page_range() undo path, pfn_to_online_page() just checks
> the first pfn in a pageblock while __first_valid_page() will traverse the
> pageblock until the first online pfn is found. So we may miss the call to
> unset_migratetype_isolate() in undo path and pages will remain isolated
> unexpectedly. Fix this by calling undo_isolate_page_range() and this will
> also help to simplify the code further.
I like the clean up part but is this a real problem that requires CC
stable? Have you ever seen this to be a real problem? It looks like
something based on reading the code.
> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> ---
> v1->v2:
> Simplify the code further per David Hildenbrand.
> ---
> mm/page_isolation.c | 20 +++-----------------
> 1 file changed, 3 insertions(+), 17 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index a95c2c6562d0..f93cc63d8fa1 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -183,7 +183,6 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> unsigned migratetype, int flags)
> {
> unsigned long pfn;
> - unsigned long undo_pfn;
> struct page *page;
>
> BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
> @@ -193,25 +192,12 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> pfn < end_pfn;
> pfn += pageblock_nr_pages) {
> page = __first_valid_page(pfn, pageblock_nr_pages);
> - if (page) {
> - if (set_migratetype_isolate(page, migratetype, flags)) {
> - undo_pfn = pfn;
> - goto undo;
> - }
> + if (page && set_migratetype_isolate(page, migratetype, flags)) {
> + undo_isolate_page_range(start_pfn, pfn, migratetype);
> + return -EBUSY;
> }
> }
> return 0;
> -undo:
> - for (pfn = start_pfn;
> - pfn < undo_pfn;
> - pfn += pageblock_nr_pages) {
> - struct page *page = pfn_to_online_page(pfn);
> - if (!page)
> - continue;
> - unset_migratetype_isolate(page, migratetype);
> - }
> -
> - return -EBUSY;
> }
>
> /*
> --
> 2.23.0
--
Michal Hocko
SUSE Labs
