On 10/11/2018 3:58 PM, Dan Williams wrote:
On Thu, Oct 11, 2018 at 3:18 PM Alexander Duyck <alexander.h.du...@linux.intel.com> wrote:The general suspicion at this point is that the setting of the reserved bit is not really needed for hotplug memory. In addition the setting of this bit results in issues for DAX in that it is not possible to assign the region to KVM if the reserved bit is set in each page. For now we can try just not setting the bit since we suspect it isn't adding value in setting it. If at a later time we find that it is needed we can come back through and re-add it for the hotplug paths. Suggested-by: Michael Hocko <mho...@suse.com> Reported-by: Dan Williams <dan.j.willi...@intel.com> Signed-off-by: Alexander Duyck <alexander.h.du...@linux.intel.com> --- mm/page_alloc.c | 11 ----------- 1 file changed, 11 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3603d5444865..e435223e2ddb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5571,8 +5571,6 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone, page = pfn_to_page(pfn); __init_single_page(page, pfn, zone, nid); - if (context == MEMMAP_HOTPLUG) - __SetPageReserved(page);At a minimum I think we need to do this before removing PageReserved, to make sure zone_device pages are not tracked in the hibernation image. diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c index 3d37c279c090..c0613137d726 100644 --- a/kernel/power/snapshot.c +++ b/kernel/power/snapshot.c @@ -1285,6 +1285,9 @@ static struct page *saveable_page(struct zone *zone, unsigned long pfn) if (swsusp_page_is_forbidden(page) || swsusp_page_is_free(page)) return NULL; + if (is_zone_device_page(page)) + return NULL; + if (PageReserved(page) && (!kernel_page_present(page) || pfn_is_nosave(pfn))) return NULL;
Yeah, I am pretty sure I broke hotplug in general with this too since it seems like it checks for the reserved flag before bringing a range online in online_pages_range.
I think I will drop this patch and go back to what I had before. There was a slight performance gain to be had for not setting the bit at all, but I think we are probably looking at yet another patch set if we want to go through and drop the need for the reserved bit to be set.
- Alex
