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

[Pankaj Gupta <pagupta@xxxxxxxxxx>]

> >> ---
> >>  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
> 

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