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Date: Mon, 27 Jul 2026 15:43:30 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: "Yadav, Arvind" <arvind.yadav@intel.com>
Cc: Balbir Singh <balbirs@nvidia.com>, <linux-mm@kvack.org>,
 <linux-kernel@vger.kernel.org>, <david@kernel.org>,
 <matthew.brost@intel.com>, <joshua.hahnjy@gmail.com>, <ziy@nvidia.com>,
 <rakie.kim@sk.com>, <byungchul@sk.com>, <gourry@gourry.net>,
 <ying.huang@linux.alibaba.com>, <apopple@nvidia.com>
Subject: Re: [PATCH v3] mm/migrate_device: Clear stale mapping after freeing
 swapcache
Message-Id: <20260727154330.cbe743a0a9518ccfe2437aac@linux-foundation.org>
In-Reply-To: <439924d5-b51a-40f7-bd96-42fa43eef0e0@intel.com>
References: <20260727053920.3494211-1-arvind.yadav@intel.com>
	<0ea36640-36bc-47a9-8d57-edc886e13aeb@nvidia.com>
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On Mon, 27 Jul 2026 16:28:42 +0530 "Yadav, Arvind" <arvind.yadav@intel.com> wrote:

> >> --- a/mm/migrate_device.c
> >> +++ b/mm/migrate_device.c
> >> @@ -1182,6 +1182,11 @@ static void __migrate_device_pages(unsigned long *src_pfns,
> >>   							 MIGRATE_PFN_COMPOUND);
> >>   					goto next;
> >>   				}
> >> +				/*
> >> +				 * reset nr so that only first after-split folio
> >> +				 * is processed below
> >> +				 */
> >> +				nr = 1;
> > We should also add a VM_WARN_ON_ONCE(folio_test_swapcache(folio))
> 
> 
> Agreed , but folio_test_swapcache()  is not valid immediately after the 
> split, as the order-0 folios may still be in swapcache.
> I’ll use just before nr = 1

AI review suggest there might be another bug in here:
	https://sashiko.dev/#/patchset/20260727053920.3494211-1-arvind.yadav@intel.com