On 2023/9/26 15:44, David Hildenbrand wrote:
On 26.09.23 04:33, Yajun Deng wrote:
When we init a single page, we need to mark this page reserved if it
does.
I failed to parse the last part of this sentence.
And some pages may not need to set page count, such as compound
pages.
Usually, the refcount of all tail pages *must* be zero. Otherwise,
get_page_unless_zero() would work on tail pages.
Can you elaborate why it should be okay here?
It means the following code in memmap_init_compound().
- __init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
+ __init_zone_device_page(page, pfn, zone_idx, nid, pgmap, 0);
prep_compound_tail(head, pfn - head_pfn);
set_page_count(page, 0);
As we can see, it will reset the page count by 'set_page_count(page, 0)'.
Therefore, we don't need to set page count in __init_zone_device_page().
I wasn't clear enough in the commit.
Maybe we can remove the 'set_page_count(page, 0)', But I didn't do
that, just to be safe.
