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Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 6/6] mm/mm_init: Fix pageblock migratetype for ZONE_DEVICE compound pages Message-ID: References: <20260415111412.1003526-1-songmuchun@bytedance.com> <20260415111412.1003526-7-songmuchun@bytedance.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260415111412.1003526-7-songmuchun@bytedance.com> Hi Muchun, On Wed, Apr 15, 2026 at 07:14:12PM +0800, Muchun Song wrote: > 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. > > Fixes: c4386bd8ee3a ("mm/memremap: add ZONE_DEVICE support for compound pages") > Signed-off-by: Muchun Song > --- > mm/mm_init.c | 42 +++++++++++++++++++++++++++--------------- > 1 file changed, 27 insertions(+), 15 deletions(-) > > diff --git a/mm/mm_init.c b/mm/mm_init.c > index f9f8e1af921c..30528c4206c1 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -674,6 +674,19 @@ static inline void fixup_hashdist(void) > static inline void fixup_hashdist(void) {} > #endif /* CONFIG_NUMA */ > > +static __meminit void pageblock_migratetype_init_range(unsigned long pfn, > + unsigned long nr_pages, > + int migratetype) > +{ > + 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(); > + } > +} > + > /* > * Initialize a reserved page unconditionally, finding its zone first. > */ > @@ -1011,21 +1024,6 @@ 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 +1120,8 @@ void __ref memmap_init_zone_device(struct zone *zone, > > __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); > > + cond_resched(); > + I don't think we want cond_resched() for every page here too, even it's a compound page :) Otherwise Reviewed-by: Mike Rapoport (Microsoft) > if (pfns_per_compound == 1) > continue; > > @@ -1129,6 +1129,18 @@ void __ref memmap_init_zone_device(struct zone *zone, > compound_nr_pages(altmap, pgmap)); > } > > + /* > + * 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() > + */ > + 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)); > } > -- > 2.20.1 > -- Sincerely yours, Mike.