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

[Luiz Capitulino]

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;
        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;
}