From: Dev Jain <dev.jain@arm.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: david@kernel.org, ljs@kernel.org, liam@infradead.org,
vbabka@kernel.org, rppt@kernel.org, surenb@google.com,
mhocko@suse.com, kasong@tencent.com, qi.zheng@linux.dev,
shakeel.butt@linux.dev, baohua@kernel.org,
axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
riel@surriel.com, harry@kernel.org, jannh@google.com,
lance.yang@linux.dev, ryan.roberts@arm.com,
anshuman.khandual@arm.com
Subject: Re: [PATCH 0/3] Batch unmap of uffd-wp file folios
Date: Thu, 16 Jul 2026 10:27:05 +0530 [thread overview]
Message-ID: <fd8dcefc-e202-495b-9190-11c04ef2ac08@arm.com> (raw)
In-Reply-To: <20260715115852.a32e472d97fa182d6a5ee482@linux-foundation.org>
On 16/07/26 12:28 am, Andrew Morton wrote:
> On Wed, 15 Jul 2026 11:18:33 +0000 Dev Jain <dev.jain@arm.com> wrote:
>
>> Currently, batched unmapping is supported if:
>>
>> 1) folio is a file folio, not belonging to uffd-wp VMA
>> 2) folio is anonymous and not swapbacked (lazyfree), not belonging to
>> uffd-wp VMA
>>
>> So the cases which are not supported are
>>
>> 1) folio belonging to uffd-wp VMA
>> 2) folio is anonymous and swapbacked
>>
>> It is easy to see that this adds a lot of cognitive load while reading
>> try_to_unmap_one - we need to remember throughout whether nr_pages == 1
>> or > 1.
>>
>> The uffd-wp handling in try_to_unmap_one is regarding preserving the
>> uffd-wp state for file folios via pte_install_uffd_wp_if_needed (for anon
>> folio, we handle that while constructing the swap pte).
>>
>> Stop special casing on uffd-wp VMAs by simply adding batching support
>> to pte_install_uffd_wp_if_needed.
>
> Thanks, I'll await reviewer input on this.
>
> Sashiko might have found a pre-existing issue:
> https://sashiko.dev/#/patchset/20260715111839.1667914-1-dev.jain@arm.com
That was unexpected from Sashiko.
"When a large folio registered with uffd-wp is unmapped via
try_to_unmap_one(), folio_unmap_pte_batch() batches and clears multiple PTEs."
At patch 2, there is no batching support yet for uffd-wp folios.
prev parent reply other threads:[~2026-07-16 4:57 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-15 11:18 [PATCH 0/3] Batch unmap of uffd-wp file folios Dev Jain
2026-07-15 11:18 ` [PATCH 1/3] mm/memory: move pte_install_uffd_wp_if_needed() into memory.c Dev Jain
2026-07-16 9:35 ` David Hildenbrand (Arm)
2026-07-16 10:06 ` Dev Jain
2026-07-15 11:18 ` [PATCH 2/3] mm/memory: batch set uffd-wp markers during zapping Dev Jain
2026-07-16 9:41 ` David Hildenbrand (Arm)
2026-07-16 10:08 ` Dev Jain
2026-07-15 11:18 ` [PATCH 3/3] mm/rmap: batch unmap file folios belonging to uffd-wp VMAs Dev Jain
2026-07-16 9:44 ` David Hildenbrand (Arm)
2026-07-15 18:58 ` [PATCH 0/3] Batch unmap of uffd-wp file folios Andrew Morton
2026-07-16 4:57 ` Dev Jain [this message]
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