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From: Muchun Song In-Reply-To: Date: Mon, 13 Apr 2026 18:07:44 +0800 Cc: Muchun Song , Andrew Morton , David Hildenbrand , Oscar Salvador , Michael Ellerman , Madhavan Srinivasan , Lorenzo Stoakes , "Liam R . 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 Content-Transfer-Encoding: quoted-printable Message-Id: <5910791C-9893-4710-9002-76534DBFBFBD@linux.dev> References: <20260405125240.2558577-1-songmuchun@bytedance.com> <20260405125240.2558577-7-songmuchun@bytedance.com> To: Mike Rapoport X-Migadu-Flow: FLOW_OUT > On Apr 13, 2026, at 17:32, Mike Rapoport wrote: >=20 > On Sun, Apr 05, 2026 at 08:51:57PM +0800, Muchun Song wrote: >> Previously, memmap_init_zone_device() only initialized 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 would remain = uninitialized. >>=20 >> This patch moves the migratetype initialization out of >> __init_zone_device_page() and into a separate function >> pageblock_migratetype_init_range(). This function iterates over the >> entire PFN range of the memory, ensuring that all pageblocks are = correctly >> initialized. >>=20 >> Fixes: c4386bd8ee3a ("mm/memremap: add ZONE_DEVICE support for = compound pages") >> Signed-off-by: Muchun Song >> --- >> mm/mm_init.c | 41 ++++++++++++++++++++++++++--------------- >> 1 file changed, 26 insertions(+), 15 deletions(-) >>=20 >> diff --git a/mm/mm_init.c b/mm/mm_init.c >> index 9a44e8458fed..4936ca78966c 100644 >> --- a/mm/mm_init.c >> +++ b/mm/mm_init.c >> @@ -674,6 +674,18 @@ static inline void fixup_hashdist(void) >> static inline void fixup_hashdist(void) {} >> #endif /* CONFIG_NUMA */ >>=20 >> +static __meminit void pageblock_migratetype_init_range(unsigned long = pfn, >> + unsigned long nr_pages, >> + int migratetype) >> +{ >> + unsigned long end =3D pfn + nr_pages; >> + >> + for (pfn =3D pageblock_align(pfn); pfn < end; pfn +=3D = pageblock_nr_pages) { >> + init_pageblock_migratetype(pfn_to_page(pfn), migratetype, false); >> + cond_resched(); >=20 > Do we need to call cond_resched() every iteration here? Of course not. >=20 >> + } >> +} >> + >> /* >> * Initialize a reserved page unconditionally, finding its zone = first. >> */ >> @@ -1011,21 +1023,6 @@ static void __ref = __init_zone_device_page(struct page *page, unsigned long pfn, >> page_folio(page)->pgmap =3D pgmap; >> page->zone_device_data =3D NULL; >>=20 >> - /* >> - * 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 +1119,8 @@ void __ref memmap_init_zone_device(struct zone = *zone, >>=20 >> __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); >>=20 >> + cond_resched(); >=20 > Originally we called cond_resched() once per pageblock, now it's = called > once per page plus for every pageblock in the tight loop that sets the > migrate type. Isn't it too much? There are indeed many more cond_resched() than before, but I don=E2=80=99t= have a concise way to write it, so I took the easy way out. How about: diff --git a/mm/mm_init.c b/mm/mm_init.c index 2d680636b67a..d13a2577c4c3 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -683,7 +683,8 @@ static __meminit void = pageblock_migratetype_init_range(unsigned long pfn, for (pfn =3D pageblock_align(pfn); pfn < end; pfn +=3D = pageblock_nr_pages) { init_pageblock_migratetype(pfn_to_page(pfn), = migratetype, isolate); - cond_resched(); + if ((pfn & (pageblock_nr_pages * 512 - 1)) =3D=3D 0) + cond_resched(); } } >=20 >> + >> if (pfns_per_compound =3D=3D 1) >> continue; >>=20 >> @@ -1129,6 +1128,18 @@ void __ref memmap_init_zone_device(struct zone = *zone, >> compound_nr_pages(altmap, pgmap)); >> } >>=20 >> + /* >> + * 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)); >> } >> --=20 >> 2.20.1 >>=20 >=20 > --=20 > Sincerely yours, > Mike.