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mm/mm_init: make memmap_init_compound() look more like prep_compound_page() 

Grepping for "prep_compound_page" leaves on clueless how devdax gets its
compound pages initialized.

Let's add a comment that might help finding this open-coded
prep_compound_page() initialization more easily.

Further, let's be less smart about the ordering of initialization and just
perform the prep_compound_head() call after all tail pages were
initialized: just like prep_compound_page() does.

No need for a comment to describe the initialization order: again, just
like prep_compound_page().

Link: https://lkml.kernel.org/r/20250901150359.867252-10-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2025-09-01 17:03:30 +02:00 committed by Andrew Morton
parent 7b4f21f5e0
commit 50765b46ab
1 changed files with 7 additions and 8 deletions
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15
mm/mm_init.c
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@ -1091,6 +1091,12 @@ static void __ref memmap_init_compound(struct page *head,
unsigned long pfn, end_pfn = head_pfn + nr_pages;
unsigned int order = pgmap->vmemmap_shift;
/*
* We have to initialize the pages, including setting up page links.
* prep_compound_page() does not take care of that, so instead we
* open-code prep_compound_page() so we can take care of initializing
* the pages in the same go.
*/
__SetPageHead(head);
for (pfn = head_pfn + 1; pfn < end_pfn; pfn++) {
struct page *page = pfn_to_page(pfn);
@ -1098,15 +1104,8 @@ static void __ref memmap_init_compound(struct page *head,
__init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
prep_compound_tail(head, pfn - head_pfn);
set_page_count(page, 0);
/*
* The first tail page stores important compound page info.
* Call prep_compound_head() after the first tail page has
* been initialized, to not have the data overwritten.
*/
if (pfn == head_pfn + 1)
prep_compound_head(head, order);
}
prep_compound_head(head, order);
}
void __ref memmap_init_zone_device(struct zone *zone,