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From: "David Hildenbrand (Arm)" <david@kernel.org>
To: Lance Yang <lance.yang@linux.dev>
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, 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,
	stable@vger.kernel.org
Subject: Re: [PATCH 2/5] mm: limit pagecache folio refcount when splicing into pipes
Date: Fri, 6 Nov 2026 22:57:19 +0100	[thread overview]
Message-ID: <6b8d6030-efe7-47d2-8aa2-3f8fd77ce95c@kernel.org> (raw)
In-Reply-To: <20261106100320.77084-1-lance.yang@linux.dev>

On 11/6/26 11:03, Lance Yang wrote:
> 
> On Thu, Nov 05, 2026 at 02:10:11PM +0100, David Hildenbrand (Arm) wrote:
>> Similar to mapping pagecache folios into page tables, let's reject splicing
>> folios into a pipe if the refcount is at it's limit, similar to how we
>> handle it during GUP.
>>
>> This will prevent more cases of possible folio refcount overflows with
>> large pagecache folios.
>>
>> Let's keep it simple and check in the two callers of
>> splice_folio_into_pipe().
>>
>> Also check in try_get_page() to cover pipe-buffer duplication by tee()
>> and partial pipe-to-pipe splicing.
> 
> What about fuse_ref_folio()? Buffered FUSE_WRITE requests can carry
> pagecache folios into a pipe through /dev/fuse without going through
> splice_folio_into_pipe() or try_get_page() ...

Of course it has its own handling ... :)

Thanks! I was hoping the number of folio references would be bounded ... I guess
one reference per pipe buffer is not the end of the world, but, let's just add
it, and fallback to copying.

-- 
Cheers,

David

  reply	other threads:[~2026-11-06 22:42 UTC|newest]

Thread overview: 29+ 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 21:23       ` David Hildenbrand (Arm)
2026-11-06 12:38   ` Kiryl Shutsemau
2026-11-06 20:54     ` David Hildenbrand (Arm)
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 21:57     ` David Hildenbrand (Arm) [this message]
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
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
2026-11-06 22:42     ` David Hildenbrand (Arm)
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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