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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CHfYdTPU; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4B35B606A31C for ; Mon, 9 Nov 2026 13:51:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CHfYdTPU Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93D081F0089F; Mon, 9 Nov 2026 13:51:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794232273; bh=AX/+bR9hzMr0c07DUMyN6/NPbIMi7uOBDTIaA+XxtRs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=CHfYdTPUz7yEX2kajRcPzZYbNfLvBf7JuKe6HfbZFEeY+6BC0bFeFHBIFhOpUanqa dnfepj2WuBLRol3na/MSWVmhqA/gtRA37iw+p0l2V0qzLz0SWbJCvq7Po1d0z6oMOh mhQ6couONZxjfLyaKSakqea+keb8tY6POfPE3YN86cnp7LE7prMOaPsWP214qxd2gN vJAH9fjiKsBgywW/rC4XDdE0sDUbZelCAmhB7VPYJI9UuTDULwxNpyJzIdufqQ3NRB eRJUtdTJuz/PVpL/DJpvSY4LbdYB2rPSqTz8PAkS8NZZz/8Z5XAWWLaEBkPTmAgxvX y7++oGi0NVr7Q== Message-ID: Date: Mon, 9 Nov 2026 14:51:06 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/migrate: fix mlock state loss when migrating PTE-mapped large folios To: Wandun Chen , hughd@google.com, akpm@linux-foundation.org, fengwei.yin@intel.com Cc: ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261109090846.1068409-1-chenwandun1@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/9/26 10:08, Wandun Chen wrote: > From: Wandun Chen > > try_to_migrate() clears PG_mlocked when unmapping the source folio. > For PTE-mapped large folios, remove_migration_pte() restores one PTE at > a time, but the rmap helpers only restore mlock for full-folio mappings. > This leaves the destination PTE-mapped large folio without PG_mlocked. > > Restore mlock once all PTEs of the destination folio are restored under > a single page table lock. > > Fixes: dc68badcede4 ("mm: mlock: update mlock_pte_range to handle large folio") > Signed-off-by: Wandun Chen > --- > mm/migrate.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 94033c222e04..140e291d4587 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -353,6 +353,7 @@ static bool remove_migration_pte(struct folio *folio, > { > struct rmap_walk_arg *rmap_walk_arg = arg; > DEFINE_FOLIO_VMA_WALK(pvmw, rmap_walk_arg->folio, vma, addr, PVMW_SYNC | PVMW_MIGRATION); > + unsigned long nr_ptes = 0; > > while (page_vma_mapped_walk(&pvmw)) { > rmap_t rmap_flags = RMAP_NONE; > @@ -446,9 +447,16 @@ static bool remove_migration_pte(struct folio *folio, > else > folio_add_file_rmap_pte(folio, new, vma); > set_pte_at(vma->vm_mm, pvmw.address, pvmw.pte, pte); > + > + nr_ptes++; > } > - if (READ_ONCE(vma->vm_flags) & VM_LOCKED) > + if (READ_ONCE(vma->vm_flags) & VM_LOCKED) { > + if (folio_test_large(folio) && > + nr_ptes == folio_nr_pages(folio) && > + !(pvmw.flags & PVMW_PGTABLE_CROSSED)) > + mlock_vma_folio(folio, vma); > mlock_drain_local(); > + } I have the recollection that the next try_to_unmap() would fix that up? Or is that not the case? The "nr_ptes == folio_nr_pages(folio)" case is shaky either way for folios that are mapped into multiple VMAs, or what's the logic behind that, such that is is fine to only focus on large folios that getting fully pte-mapped? -- Cheers, David