Re: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are logically offline
From: David Hildenbrand Sent: November 14, 2018 at 9:16:58 PM GMT > Subject: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are logically > offline > > > Right now, pages inflated as part of a balloon driver will be dumped > by dump tools like makedumpfile. While XEN is able to check in the > crash kernel whether a certain pfn is actuall backed by memory in the > hypervisor (see xen_oldmem_pfn_is_ram) and optimize this case, dumps of > virtio-balloon and hv-balloon inflated memory will essentially result in > zero pages getting allocated by the hypervisor and the dump getting > filled with this data. Is there any reason that VMware balloon driver is not mentioned? ___ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
Re: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are logically offline
From: David Hildenbrand Sent: November 14, 2018 at 11:05:38 PM GMT > Subject: Re: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are > logically offline > > > On 14.11.18 23:57, Nadav Amit wrote: >> From: David Hildenbrand >> Sent: November 14, 2018 at 9:16:58 PM GMT >>> Subject: [PATCH RFC 0/6] mm/kdump: allow to exclude pages that are >>> logically offline >>> >>> >>> Right now, pages inflated as part of a balloon driver will be dumped >>> by dump tools like makedumpfile. While XEN is able to check in the >>> crash kernel whether a certain pfn is actuall backed by memory in the >>> hypervisor (see xen_oldmem_pfn_is_ram) and optimize this case, dumps of >>> virtio-balloon and hv-balloon inflated memory will essentially result in >>> zero pages getting allocated by the hypervisor and the dump getting >>> filled with this data. >> >> Is there any reason that VMware balloon driver is not mentioned? > > Definitely ... > > ... not ;) . I haven't looked at vmware's balloon driver yet (I only saw > that there was quite some activity recently). I guess it should have > similar problems. (I mean reading and dumping data nobody cares about is > certainly not desired) > > Can you share if something like this is also desired for vmware's > implementation? (I tagged this as RFC to get some more feedback) > > It should in theory be as simple as adding a handful of > _SetPageOffline()/_ClearPageOffline() at the right spots. Thanks, I was just suspecting it is personal ;-) Actually, some patches that I sent for 4.20 to use the balloon-compaction infrastructure by the VMware balloon fell between the cracks, and I need to resend them. I would obviously prefer that your changes would be done on top of those that were skipped. This patch-set sounds very reasonable to me, but I prefer that Julien (cc’d) would also give his opinion. Regards, Nadav ___ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
Re: [PATCH v1 6/8] vmw_balloon: mark inflated pages PG_offline
Thanks for this patch!
> On Nov 19, 2018, at 2:16 AM, David Hildenbrand wrote:
>
> Mark inflated and never onlined pages PG_offline, to tell the world that
> the content is stale and should not be dumped.
>
> Cc: Xavier Deguillard
> Cc: Nadav Amit
> Cc: Arnd Bergmann
> Cc: Greg Kroah-Hartman
> Cc: Julien Freche
> Cc: Andrew Morton
> Cc: Matthew Wilcox
> Cc: Michal Hocko
> Cc: "Michael S. Tsirkin"
> Signed-off-by: David Hildenbrand
> ---
> drivers/misc/vmw_balloon.c | 32
> 1 file changed, 32 insertions(+)
>
> diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
> index e6126a4b95d3..8cc8bd9a4e32 100644
> --- a/drivers/misc/vmw_balloon.c
> +++ b/drivers/misc/vmw_balloon.c
> @@ -544,6 +544,36 @@ unsigned int vmballoon_page_order(enum
> vmballoon_page_size_type page_size)
> return page_size == VMW_BALLOON_2M_PAGE ? VMW_BALLOON_2M_ORDER : 0;
> }
>
> +/**
> + * vmballoon_mark_page_offline() - mark a page as offline
> + * @page: pointer for the page
If possible, please add a period at the end of the sentence (yes, I know I
got it wrong in some places too).
> + * @page_size: the size of the page.
> + */
> +static void
> +vmballoon_mark_page_offline(struct page *page,
> + enum vmballoon_page_size_type page_size)
> +{
> + int i;
> +
> + for (i = 0; i < 1ULL << vmballoon_page_order(page_size); i++)
Can you please do instead:
unsigned int;
for (i = 0; i < vmballoon_page_in_frames(page_size); i++)
> + __SetPageOffline(page + i);
> +}
> +
> +/**
> + * vmballoon_mark_page_online() - mark a page as online
> + * @page: pointer for the page
> + * @page_size: the size of the page.
> + */
> +static void
> +vmballoon_mark_page_online(struct page *page,
> +enum vmballoon_page_size_type page_size)
> +{
> + int i;
> +
> + for (i = 0; i < 1ULL << vmballoon_page_order(page_size); i++)
> + __ClearPageOffline(page + i);
Same here (use vmballoon_page_in_frames).
> +}
> +
> /**
> * vmballoon_page_in_frames() - returns the number of frames in a page.
> * @page_size: the size of the page.
> @@ -612,6 +642,7 @@ static int vmballoon_alloc_page_list(struct vmballoon *b,
>ctl->page_size);
>
> if (page) {
> + vmballoon_mark_page_offline(page, ctl->page_size);
> /* Success. Add the page to the list and continue. */
> list_add(&page->lru, &ctl->pages);
> continue;
> @@ -850,6 +881,7 @@ static void vmballoon_release_page_list(struct list_head
> *page_list,
>
> list_for_each_entry_safe(page, tmp, page_list, lru) {
> list_del(&page->lru);
> + vmballoon_mark_page_online(page, page_size);
> __free_pages(page, vmballoon_page_order(page_size));
> }
We would like to test it in the next few days, but in the meanwhile, after
you address these minor issues:
Acked-by: Nadav Amit
Thanks again,
Nadav
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