From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-118.mta0.migadu.com [91.218.175.118]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF78D25A321 for ; Sat, 10 Oct 2026 01:13:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.118 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791594784; cv=none; b=U7nGJfplIRuWRHJVEPygj5RtM5GMnacG/DiXnzJHzruw7P6IEqo/pG9W8E2XaOog6c8p0oIs+RR9HSxF2DVlQxWllz9eQzRtgJxfoWrFC3GKK5JMzj7w4t9SsfhsRclPiPOhApJWv5kFU50Kg28ivyu0YI54P8XtB24uCHjcLss= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791594784; c=relaxed/simple; bh=vgSSjwqoJ3UL9SpCaxLIlO+CXMUgBIurc/MPR7NqdSQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XvYOylWINM12RxSR5yXgON51X0HwFrWTpXUcYiWrbOqXRBLcFXiCcFyopFNURSovF8isgZzOcYbdZQgV2tFCa0lvkALjV9KQGGCs1TqLBDN6nG6RlA6BB2rDtwCZ+RrwX4LRXC9dnbFUDM7cktUuLK4XW52vBPsdM8llQ6GuEug= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=hg2oA4vQ; arc=none smtp.client-ip=91.218.175.118 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) header.d=linux.dev header.i=@linux.dev header.b="hg2oA4vQ" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=vgSSjwqoJ3UL9SpCaxLIlO+CXMUgBIurc/MPR7NqdSQ=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791594779; v=1; x=1792199579; b=hg2oA4vQ4SiQPWoa8gt3sTBnuZs5ox+3Syuyla4g6zq7cwfE7gZ7i2ogDBFoZ6CPz1E3rvwb fi/y0+u+GpiJhDbLHzmTZXahtcfAEj0395D9giLkuVTrZdDXiyNl3IBzP6abI/zZ1ABYftNIBhX mQQ22QPZE/KkYgeLlBN55gJw= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 9e75b8b92041ffeb; Sat, 10 Oct 2026 01:12:59 +0000 X-Mizu-Trace-ID: 9e75b8b92041ffeb X-Migadu-Flow: FLOW_OUT Message-ID: <0ec81c65-fbf5-405f-948b-0fb1b2e083e8@linux.dev> Date: Sat, 10 Oct 2026 09:12:48 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/huge_memory: avoid transient none PMDs during lazyfree reclaim To: "David Hildenbrand (Arm)" , Zi Yan Cc: Kyle Zeng , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Usama Arif , Kiryl Shutsemau , stable@vger.kernel.org References: <20261009165214.40212-2-kylebot@openai.com> <8db35dc0-eb06-42e4-90f9-534522e810e1@kernel.org> <55765FF3-18D7-424C-984D-81C316F323E1@nvidia.com> Content-Language: en-US From: Lance Yang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2026/10/10 04:44, David Hildenbrand (Arm) wrote: > On 10/9/26 22:27, Zi Yan wrote: >> On 9 Oct 2026, at 16:23, David Hildenbrand (Arm) wrote: >> >>> On 10/9/26 20:17, Zi Yan wrote: >>>> >>>> There are some gaps we need to close before getting this fix in: >>>> >>>> 1. GUP-fast cannot follow the invalidated PMD: riscv and LoongArch need >>>> pmd_access_permitted() that requires _PAGE_PRESENT; s390's >>>> pmdp_invalidate() needs a change. >>> >>> Ugh. We really need pmdp_invalidate() to have reasonable semantics. This whole >>> PMD locking is a mess :( >>> >>>> >>>> 2. sparc64's thp_pte_count can be imbalanced with this change (based on >>>> Lance's offlist feedback). >>> >>> Ack. >>> >>>> >>>> In addition, powerpc has a page table check issue similr to riscv, where riscv >>>> fixed it with commit 9f4a88b8d01a6. This is not related to this issue >>>> but discovered along with the investigation. >>> >>> Zi, do you have the capacity to take over this patch? >> >> Yes, I can take over it. My plan is to send a series including >> patches for 1 and this patch as is. powerpc fix can be a separate one. >> >> Best Regards, >> Yan, Zi > > If we need a quick stable fix we could temporarily disable the whole thing until > it is fixed, just a thought. +1 we could do that for now. A quick fix with minimal churn (correctness comes first).