From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 60B0D37FF79 for ; Mon, 13 Apr 2026 13:28:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776086910; cv=none; b=frv+IcHX4zVJU/kDOVbpXT073BuRYstt9qknnm65rZ7GgArnjrXU+83wTbW8Am1KceD7KyrhNq1gCle8LpVoFcrx2thbjtS4NtebMGi8Qq8lYmqLw2lnrni6Ws5VAlCG4PODWxhFQK85SrZDW8VED6ClKuTBDSr6nI3puOkmQ/k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776086910; c=relaxed/simple; bh=7VByJTwrbtmSQuR7FvCes1Iak+N/IKd4uFjkgcO39ug=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VbMojISHBFwQ/jgC9yA57JFgkErBFLiQuf0xWtK2D3PeSFILkIijbUgRwYLXDFY4OXAkI/8NTh9HbKNY1wTG7PTAbP/IMUM4KjKAUKOXBJEBNrHkkyXFam8hmPRhyP+G736llaAWx8nMIsSdFneMrhri1Js+dtlZQyp1CT+YjtY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mQZFa8uj; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="mQZFa8uj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1FF49C2BCAF; Mon, 13 Apr 2026 13:28:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776086910; bh=7VByJTwrbtmSQuR7FvCes1Iak+N/IKd4uFjkgcO39ug=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mQZFa8ujuVe81yE8vcLgLxhVVWJzt+swKGWZ2ofKQXeOaAczk3K7ksXwrVlaJ+hYw yVXg5XiKV2rDDSHGmZ1cHQ+6AGEE+yBrBY8Yi+AJDfc5p1i4llszFa2XXvV01sTTec G5SA0gcFv2AQ1usMg1UopmrqtMVJnc6aLQ9KCriHB4Wjq3rdjlaeimKxzpGP4Tcub0 Hpe1GUFInfON7xos/qUF6Ek0JOQtQ+M2Mm8BtjbuE4GPPPko8pTQjSqAPoaHfBPtIj Zk8VEGEOVMkuyQZ4NDKGfZm/7c5eMmPrWTp1byTgwQsPAwlXcKcEJE+KRr1I5UgG+L OZ747izg6AIcw== Date: Mon, 13 Apr 2026 16:28:21 +0300 From: Mike Rapoport To: Muchun Song 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 Subject: Re: [PATCH 06/49] mm/mm_init: fix uninitialized pageblock migratetype for ZONE_DEVICE compound pages Message-ID: References: <20260405125240.2558577-1-songmuchun@bytedance.com> <20260405125240.2558577-7-songmuchun@bytedance.com> <5910791C-9893-4710-9002-76534DBFBFBD@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5910791C-9893-4710-9002-76534DBFBFBD@linux.dev> On Mon, Apr 13, 2026 at 06:07:44PM +0800, Muchun Song wrote: > > > > On Apr 13, 2026, at 17:32, Mike Rapoport wrote: > > > > 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. > >> > >> 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. > >> > >> 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(-) > >> > >> 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 */ > >> > >> +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); > >> + cond_resched(); > > > > Do we need to call cond_resched() every iteration here? > > Of course not. > > > > >> + } > >> +} > >> + > >> /* > >> * 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 = 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 +1119,8 @@ void __ref memmap_init_zone_device(struct zone *zone, > >> > >> __init_zone_device_page(page, pfn, zone_idx, nid, pgmap); > >> > >> + cond_resched(); > > > > 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’t 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 = pageblock_align(pfn); pfn < end; pfn += pageblock_nr_pages) { > init_pageblock_migratetype(pfn_to_page(pfn), migratetype, isolate); > - cond_resched(); > + if ((pfn & (pageblock_nr_pages * 512 - 1)) == 0) > + cond_resched(); TBH, I don't know if 512 is the right number :) pageblock boundary was a convenient point to have cond_resched() along with setting the migrate type. Here we might be able to squeeze more iterations between subsequent cond_resched() calls. -- Sincerely yours, Mike.