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From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: David Hildenbrand <david@redhat.com>,
	"Mike Rapoport (Microsoft)" <rppt@kernel.org>,
	Wei Yang <richard.weiyang@gmail.com>,
	Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
	"Liam R. Howlett" <Liam.Howlett@oracle.com>,
	Alexander Potapenko <glider@google.com>,
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	Zi Yan <ziy@nvidia.com>
Subject: [PATCH v2 09/37] mm/mm_init: make memmap_init_compound() look more like prep_compound_page()
Date: Mon,  1 Sep 2025 17:03:30 +0200	[thread overview]
Message-ID: <20250901150359.867252-10-david@redhat.com> (raw)
In-Reply-To: <20250901150359.867252-1-david@redhat.com>

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().

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: David Hildenbrand <david@redhat.com>
---
 mm/mm_init.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 5c21b3af216b2..df614556741a4 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -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,
-- 
2.50.1


  parent reply	other threads:[~2025-09-01 15:07 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-01 15:03 [PATCH v2 00/37] mm: remove nth_page() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 01/37] mm: stop making SPARSEMEM_VMEMMAP user-selectable David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 02/37] arm64: Kconfig: drop superfluous "select SPARSEMEM_VMEMMAP" David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 03/37] s390/Kconfig: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 04/37] x86/Kconfig: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 05/37] wireguard: selftests: remove CONFIG_SPARSEMEM_VMEMMAP=y from qemu kernel config David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 06/37] mm/page_alloc: reject unreasonable folio/compound page sizes in alloc_contig_range_noprof() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 07/37] mm/memremap: reject unreasonable folio/compound page sizes in memremap_pages() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 08/37] mm/hugetlb: check for unreasonable folio sizes when registering hstate David Hildenbrand
2025-09-01 15:03 ` David Hildenbrand [this message]
2025-09-01 15:03 ` [PATCH v2 10/37] mm: sanity-check maximum folio size in folio_set_order() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 11/37] mm: limit folio/compound page sizes in problematic kernel configs David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 12/37] mm: simplify folio_page() and folio_page_idx() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 13/37] mm/hugetlb: cleanup hugetlb_folio_init_tail_vmemmap() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 14/37] mm/mm/percpu-km: drop nth_page() usage within single allocation David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 15/37] fs: hugetlbfs: remove nth_page() usage within folio in adjust_range_hwpoison() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 16/37] fs: hugetlbfs: cleanup " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 17/37] mm/pagewalk: drop nth_page() usage within folio in folio_walk_start() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 18/37] mm/gup: drop nth_page() usage within folio when recording subpages David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 19/37] mm/gup: remove record_subpages() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 20/37] io_uring/zcrx: remove nth_page() usage within folio David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 21/37] mips: mm: convert __flush_dcache_pages() to __flush_dcache_folio_pages() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 22/37] mm/cma: refuse handing out non-contiguous page ranges David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 23/37] dma-remap: drop nth_page() in dma_common_contiguous_remap() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 24/37] scatterlist: disallow non-contigous page ranges in a single SG entry David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 25/37] ata: libata-sff: drop nth_page() usage within " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 26/37] drm/i915/gem: " David Hildenbrand
2025-09-02  9:22   ` Tvrtko Ursulin
2025-09-02  9:42     ` David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 27/37] mspro_block: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 28/37] memstick: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 29/37] mmc: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 30/37] scsi: scsi_lib: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 31/37] scsi: sg: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 32/37] vfio/pci: " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 33/37] crypto: remove " David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 34/37] mm/gup: drop nth_page() usage in unpin_user_page_range_dirty_lock() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 35/37] kfence: drop nth_page() usage David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 36/37] block: update comment of "struct bio_vec" regarding nth_page() David Hildenbrand
2025-09-01 15:03 ` [PATCH v2 37/37] mm: remove nth_page() David Hildenbrand

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