From: Lance Yang <lance.yang@linux.dev>
To: david@kernel.org
Cc: akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org,
vbabka@kernel.org, rppt@kernel.org, surenb@google.com,
mhocko@suse.com, willy@infradead.org, jack@suse.cz,
ziy@nvidia.com, baolin.wang@linux.alibaba.com,
nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com,
baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev,
kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com,
byungchul@sk.com, gourry@gourry.net,
ying.huang@linux.alibaba.com, apopple@nvidia.com,
peterx@redhat.com, hannes@cmpxchg.org, songliubraving@fb.com,
riel@surriel.com, hughd@google.com, will@kernel.org,
aneesh.kumar@kernel.org, npiggin@gmail.com, peterz@infradead.org,
jgg@ziepe.ca, kevin.tian@intel.com, joro@8bytes.org,
robin.murphy@arm.com, steven.sistare@oracle.com,
jhubbard@nvidia.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-arch@vger.kernel.org, iommu@lists.linux.dev,
mason@kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH 3/5] mm/mmu_gather: flush pending references early before the folio limit
Date: Fri, 6 Nov 2026 23:15:33 +0800 [thread overview]
Message-ID: <20261106151533.89428-1-lance.yang@linux.dev> (raw)
In-Reply-To: <20261105-refcount_overflow_stable-v1-3-70b9c655da3e@kernel.org>
On Thu, Nov 05, 2026 at 02:10:12PM +0100, David Hildenbrand (Arm) wrote:
>When a task zaps mappings (e.g., MADV_DONTNEED), it can drop the PT lock
>and defer dropping the folio references. In the meantime, page faults
>can refault pagecache folios, creating more references for the same
>folios.
>
>Let's just request a flush after enqueueing a pagecache folio whose
>refcount reached a certain threshold. Start flushing well before new
>references are refused, regardless of the caller's privileges.
>
>This is a temporary measure until we have something better.
>
>Reported-by: Chris Mason <mason@kernel.org>
>Fixes: 10ebac4f95e7 ("mm/memory: optimize unmap/zap with PTE-mapped THP")
>Cc: stable@vger.kernel.org
>Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>---
Reviewed-by: Lance Yang <lance.yang@linux.dev>
next prev parent reply other threads:[~2026-11-06 15:15 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-05 13:10 [PATCH 0/5] mm: limit pagecache folio refcount David Hildenbrand (Arm)
2026-11-05 13:10 ` [PATCH 1/5] mm: limit pagecache folio refcount when mapping pages David Hildenbrand (Arm)
2026-11-06 9:11 ` Lance Yang
2026-11-06 9:42 ` Jose A. Perez de Azpillaga
2026-11-06 10:05 ` David Hildenbrand (Arm)
2026-11-06 10:06 ` Lance Yang
2026-11-06 12:38 ` Kiryl Shutsemau
2026-11-05 13:10 ` [PATCH 2/5] mm: limit pagecache folio refcount when splicing into pipes David Hildenbrand (Arm)
2026-11-06 9:50 ` Jose A. Perez de Azpillaga
2026-11-06 10:03 ` Lance Yang
2026-11-06 17:58 ` Josef Bacik
2026-11-06 20:09 ` David Hildenbrand (Arm)
2026-11-06 20:43 ` Jason Gunthorpe
2026-11-06 20:45 ` David Hildenbrand (Arm)
2026-11-05 13:10 ` [PATCH 3/5] mm/mmu_gather: flush pending references early before the folio limit David Hildenbrand (Arm)
2026-11-06 9:56 ` Jose A. Perez de Azpillaga
2026-11-06 15:15 ` Lance Yang [this message]
2026-11-05 13:10 ` [PATCH 4/5] iommufd: fix cleanup when adding memfd folio pins fails David Hildenbrand (Arm)
2026-11-06 15:39 ` Lance Yang
2026-11-06 20:46 ` Jason Gunthorpe
2026-11-05 13:10 ` [PATCH 5/5] mm/gup: limit pagecache folio refcount when grabbing references David Hildenbrand (Arm)
2026-11-06 10:13 ` Jose A. Perez de Azpillaga
2026-11-05 17:51 ` [PATCH 0/5] mm: limit pagecache folio refcount David Hildenbrand (Arm)
2026-11-06 19:49 ` Josef Bacik
2026-11-06 20:31 ` David Hildenbrand (Arm)
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