Re: linux-next: manual merge of the slab tree with the mm-unstable tree

[Vlastimil Babka]

On 7/21/25 23:35, Luiz Capitulino wrote:
> On 2025-07-21 15:38, Matthew Wilcox wrote:
>> On Mon, Jul 21, 2025 at 02:20:01PM +1000, Stephen Rothwell wrote:
>>> Hi all,
>>>
>>> Today's linux-next merge of the slab tree got a conflict in:
>>>
>>>    fs/proc/page.c
>>>
>>> between commit:
>>>
>>>    a602ee331e31 ("fs: stable_page_flags(): use snapshot_page()")
>>>
>>> from the mm-unstable tree and commit:
>>>
>>>    d8178294c53e ("proc: Remove mention of PG_slab")
>>>
>>> from the slab tree.
>>>
>>> I fixed it up (I just used the former version) and can carry the fix as
>>> necessary. This is now fixed as far as linux-next is concerned, but any
>> 
>> I think the snapshot_page commit was incorrect in removing this comment.
>> It is still valuable information.  I think the comment from d8178294c53e
>> should remain in the tree after the resolution.
> 
> The comment wasn't just dropped, David suggested a new version for the comment
> (which is similar to yours). The new comment is now part of set_ps_flags()
> which is where we set this flag in the snapshot_page() implementation:
> 
> static void set_ps_flags(struct page_snapshot *ps, const struct folio *folio,
>                           const struct page *page)
> {
>          /*
>           * Only the first page of a high-order buddy page has PageBuddy() set.
>           * So we have to check manually whether this page is part of a high-
>           * order buddy page.
>           */
>          if (PageBuddy(page))
>                  ps->flags |= PAGE_SNAPSHOT_PG_BUDDY;

That seems to work. I can therefore simply drop d8178294c53e from the slab tree.

>          else if (page_count(page) == 0 && is_free_buddy_page(page))
>                  ps->flags |= PAGE_SNAPSHOT_PG_BUDDY;
> 
>          if (folio_test_idle(folio))
>                  ps->flags |= PAGE_SNAPSHOT_PG_IDLE;
> }
>