From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.213 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793978143; b=k35Zfx6O5C1xL8cS8eQz99GyCRlOH/kxY1+dD3ST7NEDoV1L+8jjfpQc4TDIPwjJYvUc lP8SdYYEJDqwD3YMtm476PiNEituW6wi9M42ct2HBq8X2RToGPk3LVjaZ4A6+175wdwSw jNRPiyyrXmSMO9x+p+GHlwW2ifrfPSf3D4XactSZxCrb00DW/r2utvtvr7Ds7Pkub/gQa jSwNcBHhZiBFasxpl8M090QU8Nfipfq23C/lzJwR+oT2PXITKDMj3ncbqgbojWoEJJwCX Ws0HicuWfurrCGL/ReD7hACP1ZETJvN5qTd4sblJuOlep3s5CjXUITD9b8UFjva8TOA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793978143; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:From:To:Cc:Subject:Date:Message-ID: X-Mailer:In-Reply-To:References:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=BQ98lptuezRaClL/2frvW7Abmv8umTPGLgyOyGvfOsk=; b=h4RsehrapmwaAvjqOEhxcEAgfLjjJIhTCnXJs987zz40bkNZdnqeMWgVOUWmfaqM7XCH wpuhCiDva4BS0+dcFmPeT/ks+Bc064iWflihS/b8+ogOhblIlUjkZV+05Pjbb9K+C2tE7 Ucz3YRoUR9y3abQTCGdLiwAX1vAodkagoh9wjAAw7jPG/2ZpSHztW7fahkNV9FnENsYkI QudVLsW2h8fRf+/m046TM2VAkA9NNxnac6/PFwWI3ShjxE+DkxQcJrimQEycO9Z/+kYKz XIUUfTI/6VqioeWHWNQCvob/U7UczSzLGL1TECE2XondHtA9Kd+e3Wd1zR5D9r629wg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=BS+wWOBp; arc=none smtp.remote-ip=91.218.175.213 Received: from mta0.migadu.com (out-213.mta0.migadu.com [91.218.175.213]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C3902606A32D for ; Fri, 6 Nov 2026 15:15:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org C3902606A32D Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=BS+wWOBp X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=BQ98lptuezRaClL/2frvW7Abmv8umTPGLgyOyGvfOsk=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793978139; v=1; x=1794582939; b=BS+wWOBpkanXuDOzgufMBLVEhna7aL+1g1sop8joueXjNrvUxsu52rtxyL4e5+hOz9zL8jlw Rh9ddG2x6Kkkn/xyndIPS43SbZU39nj7wSqa7RQPOvmrrvbiMp0l4BaQy2ZZCzgMAJU5DmfDGTC wzRss1N8g3/8HPDXGEJwL1DY= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 8657a346237bb2f3; Fri, 06 Nov 2026 15:15:39 +0000 X-Mizu-Trace-ID: 8657a346237bb2f3 X-Migadu-Flow: FLOW_OUT From: Lance Yang 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 Message-ID: <20261106151533.89428-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261105-refcount_overflow_stable-v1-3-70b9c655da3e@kernel.org> References: <20261105-refcount_overflow_stable-v1-3-70b9c655da3e@kernel.org> 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 >Fixes: 10ebac4f95e7 ("mm/memory: optimize unmap/zap with PTE-mapped THP") >Cc: stable@vger.kernel.org >Signed-off-by: David Hildenbrand (Arm) >--- Reviewed-by: Lance Yang