Re: [PATCH v1 5/8] hv_balloon: mark inflated pages PG_offline

From: Pankaj Gupta
Date: Tue Nov 20 2018 - 04:37:21 EST



> >> ---
> >> drivers/hv/hv_balloon.c | 14 ++++++++++++--
> >> 1 file changed, 12 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
> >> index 211f3fe3a038..47719862e57f 100644
> >> --- a/drivers/hv/hv_balloon.c
> >> +++ b/drivers/hv/hv_balloon.c
> >> @@ -681,8 +681,13 @@ static struct notifier_block hv_memory_nb = {
> >> /* Check if the particular page is backed and can be onlined and online
> >> it.
> >> */
> >> static void hv_page_online_one(struct hv_hotadd_state *has, struct page
> >> *pg)
> >> {
> >> - if (!has_pfn_is_backed(has, page_to_pfn(pg)))
> >> + if (!has_pfn_is_backed(has, page_to_pfn(pg))) {
> >> + if (!PageOffline(pg))
> >> + __SetPageOffline(pg);
> >> return;
> >> + }
> >> + if (PageOffline(pg))
> >> + __ClearPageOffline(pg);
> >>
> >> /* This frame is currently backed; online the page. */
> >> __online_page_set_limits(pg);
> >> @@ -1201,6 +1206,7 @@ static void free_balloon_pages(struct
> >> hv_dynmem_device
> >> *dm,
> >>
> >> for (i = 0; i < num_pages; i++) {
> >> pg = pfn_to_page(i + start_frame);
> >> + __ClearPageOffline(pg);
> >
> > Just thinking, do we need to care for clearing PageOffline flag before
> > freeing
> > a balloon'd page?
>
> Yes we have to otherwise the code will crash when trying to set PageBuddy.
>
> (only one page type at a time may be set right now, and it makes sense.
> A page that is offline cannot e.g. be a buddy page)

o.k
>
> So PageOffline is completely managed by the page owner.

Makes sense. Thanks for explaining.

Pankaj
>
> >
> > Thanks,
> > Pankaj
>
>
> --
>
> Thanks,
>
> David / dhildenb
>