From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 94FEEEB64D9 for ; Wed, 12 Jul 2023 08:16:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232170AbjGLIQH (ORCPT ); Wed, 12 Jul 2023 04:16:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232223AbjGLIP2 (ORCPT ); Wed, 12 Jul 2023 04:15:28 -0400 X-Greylist: delayed 604 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Wed, 12 Jul 2023 01:14:33 PDT Received: from out-52.mta1.migadu.com (out-52.mta1.migadu.com [95.215.58.52]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A45AD19B6 for ; Wed, 12 Jul 2023 01:14:33 -0700 (PDT) Content-Type: text/plain; charset=us-ascii DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1689149066; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1kQGtHc+N0kBzheMdTFEuRcExKmasAznpDZbENi8pLk=; b=h+DR9B2FISyzDGCFrq/K/NU6zpYWWVYhJgPEvBQCkSLqHUchXRPV5dvh81F5Hdkp6mVqoq mP/bwmQWfPEHqkySzty5kKM8gG5qRRYhgkXuqh74BgJf63KBhO2lKDeijzxBP6b0gIEDaK KWikBffTqmCQxjje3bOwzeZUP4af+Ns= MIME-Version: 1.0 Subject: Re: [PATCH 1/2] hugetlb: Do not clear hugetlb dtor until allocating vmemmap X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Muchun Song In-Reply-To: <20230711220942.43706-2-mike.kravetz@oracle.com> Date: Wed, 12 Jul 2023 16:03:42 +0800 Cc: Linux Memory Management List , LKML , Jiaqi Yan , Naoya Horiguchi , Muchun Song , Miaohe Lin , Axel Rasmussen , James Houghton , Michal Hocko , Andrew Morton , stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <4469DCBD-59B4-41F2-A097-E5F01DD9E967@linux.dev> References: <20230711220942.43706-1-mike.kravetz@oracle.com> <20230711220942.43706-2-mike.kravetz@oracle.com> To: Mike Kravetz X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org > On Jul 12, 2023, at 06:09, Mike Kravetz = wrote: >=20 > Freeing a hugetlb page and releasing base pages back to the underlying > allocator such as buddy or cma is performed in two steps: > - remove_hugetlb_folio() is called to remove the folio from hugetlb > lists, get a ref on the page and remove hugetlb destructor. This > all must be done under the hugetlb lock. After this call, the page > can be treated as a normal compound page or a collection of base > size pages. > - update_and_free_hugetlb_folio() is called to allocate vmemmap if > needed and the free routine of the underlying allocator is called > on the resulting page. We can not hold the hugetlb lock here. >=20 > One issue with this scheme is that a memory error could occur between > these two steps. In this case, the memory error handling code treats > the old hugetlb page as a normal compound page or collection of base > pages. It will then try to SetPageHWPoison(page) on the page with an > error. If the page with error is a tail page without vmemmap, a write > error will occur when trying to set the flag. >=20 > Address this issue by modifying remove_hugetlb_folio() and > update_and_free_hugetlb_folio() such that the hugetlb destructor is = not > cleared until after allocating vmemmap. Since clearing the destructor > requires holding the hugetlb lock, the clearing is done in > remove_hugetlb_folio() if the vmemmap is present. This saves a > lock/unlock cycle. Otherwise, destructor is cleared in > update_and_free_hugetlb_folio() after allocating vmemmap. >=20 > Note that this will leave hugetlb pages in a state where they are = marked > free (by hugetlb specific page flag) and have a ref count. This is = not > a normal state. The only code that would notice is the memory error > code, and it is set up to retry in such a case. >=20 > A subsequent patch will create a routine to do bulk processing of > vmemmap allocation. This will eliminate a lock/unlock cycle for each > hugetlb page in the case where we are freeing a large number of pages. >=20 > Fixes: ad2fa3717b74 ("mm: hugetlb: alloc the vmemmap pages associated = with each HugeTLB page") > Cc: > Signed-off-by: Mike Kravetz Hi Mike, I have seen an issue proposed by Jiaqi Yan in [1]. I didn't see any resolution for it. Am I missing something with this fix? [1] = https://lore.kernel.org/linux-mm/CACw3F53iPiLrJt4pyaX2aaZ5BVg9tj8x_k6-v7=3D= 9Xn1nrh=3DUCw@mail.gmail.com/ Thanks.=