mm/mm_init: fix pageblock migratetype for ZONE_DEVICE compound pages

The memmap_init_zone_device() function only initializes the migratetype of
the first pageblock of a compound page.  If the compound page size exceeds
pageblock_nr_pages (e.g., 1GB hugepages with 2MB pageblocks), subsequent
pageblocks in the compound page remain uninitialized.

Move the migratetype initialization out of __init_zone_device_page() and
into a separate pageblock_migratetype_init_range() function.  This
iterates over the entire PFN range of the memory, ensuring that all
pageblocks are correctly initialized.

Also remove the stale confusing comment about MEMINIT_HOTPLUG above the
migratetype setting since it is an obsolete relic from commit 966cf44f637e
("mm: defer ZONE_DEVICE page initialization to the point where we init
pgmap") and no longer makes sense here.

Link: https://lore.kernel.org/20260428081855.1249045-6-songmuchun@bytedance.com
Fixes: c4386bd8ee3a ("mm/memremap: add ZONE_DEVICE support for compound pages")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Liam R. Howlett <liam@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Joao Martins <joao.m.martins@oracle.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mm_init.c b/mm/mm_init.c
index f9f8e1af921cda91d812cffdad2f1a0698cfd6ac..cfc76953e249c122b72cb8121d3809314fa19314 100644 (file)
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -674,6 +674,20 @@ static inline void fixup_hashdist(void)
 static inline void fixup_hashdist(void) {}
 #endif /* CONFIG_NUMA */
 
+#ifdef CONFIG_ZONE_DEVICE
+static __meminit void pageblock_migratetype_init_range(unsigned long pfn,
+               unsigned long nr_pages, int migratetype)
+{
+       const unsigned long end = pfn + nr_pages;
+
+       for (pfn = pageblock_align(pfn); pfn < end; pfn += pageblock_nr_pages) {
+               init_pageblock_migratetype(pfn_to_page(pfn), migratetype, false);
+               if (IS_ALIGNED(pfn, PAGES_PER_SECTION))
+                       cond_resched();
+       }
+}
+#endif
+
 /*
  * Initialize a reserved page unconditionally, finding its zone first.
  */
@@ -1011,21 +1025,6 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
        page_folio(page)->pgmap = pgmap;
        page->zone_device_data = NULL;
 
-       /*
-        * Mark the block movable so that blocks are reserved for
-        * movable at startup. This will force kernel allocations
-        * to reserve their blocks rather than leaking throughout
-        * the address space during boot when many long-lived
-        * kernel allocations are made.
-        *
-        * Please note that MEMINIT_HOTPLUG path doesn't clear memmap
-        * because this is done early in section_activate()
-        */
-       if (pageblock_aligned(pfn)) {
-               init_pageblock_migratetype(page, MIGRATE_MOVABLE, false);
-               cond_resched();
-       }
-
        /*
         * ZONE_DEVICE pages other than MEMORY_TYPE_GENERIC are released
         * directly to the driver page allocator which will set the page count
@@ -1122,6 +1121,9 @@ void __ref memmap_init_zone_device(struct zone *zone,
 
                __init_zone_device_page(page, pfn, zone_idx, nid, pgmap);
 
+               if (IS_ALIGNED(pfn, PAGES_PER_SECTION))
+                       cond_resched();
+
                if (pfns_per_compound == 1)
                        continue;
 
@@ -1129,6 +1131,8 @@ void __ref memmap_init_zone_device(struct zone *zone,
                                     compound_nr_pages(altmap, pgmap));
        }
 
+       pageblock_migratetype_init_range(start_pfn, nr_pages, MIGRATE_MOVABLE);
+
        pr_debug("%s initialised %lu pages in %ums\n", __func__,
                nr_pages, jiffies_to_msecs(jiffies - start));
 }