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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id C762CC433EF for ; Mon, 7 Mar 2022 12:20:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 25D0F8D0002; Mon, 7 Mar 2022 07:20:22 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1F1758D0001; Mon, 7 Mar 2022 07:20:22 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0D7558D0002; Mon, 7 Mar 2022 07:20:22 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0110.hostedemail.com [216.40.44.110]) by kanga.kvack.org (Postfix) with ESMTP id F33D18D0001 for ; Mon, 7 Mar 2022 07:20:21 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A9B40A7C2A for ; Mon, 7 Mar 2022 12:20:21 +0000 (UTC) X-FDA: 79217497842.20.41A05FD Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf10.hostedemail.com (Postfix) with ESMTP id D0850C0006 for ; Mon, 7 Mar 2022 12:20:20 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KBy8g0p0mz1GC9j; Mon, 7 Mar 2022 20:15:31 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Mon, 7 Mar 2022 20:20:16 +0800 Subject: Re: [PATCH 13/16] mm/migration: return errno when isolate_huge_page failed To: Baolin Wang , CC: , , , , , , , , , , , , , , , , , References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-14-linmiaohe@huawei.com> From: Miaohe Lin Message-ID: Date: Mon, 7 Mar 2022 20:20:16 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D0850C0006 X-Stat-Signature: 4gqg9mcfpr39u81e3soe4ww1w8xt6i44 Authentication-Results: imf10.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf10.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-HE-Tag: 1646655620-493203 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/3/7 10:14, Baolin Wang wrote: > Hi Miaohe, >=20 > On 3/4/2022 5:34 PM, Miaohe Lin wrote: >> We should return errno (-EBUSY here) when failed to isolate the huge p= age >> rather than always return 1 which could confuse the user. >> >> Signed-off-by: Miaohe Lin >> --- >> =C2=A0 mm/migrate.c | 6 ++---- >> =C2=A0 1 file changed, 2 insertions(+), 4 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 6c2dfed2ddb8..279940c0c064 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1618,10 +1618,8 @@ static int add_page_for_migration(struct mm_str= uct *mm, unsigned long addr, >> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 goto out_putpag= e; >> =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (PageHuge(page)) { >> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (PageHead(page)) { >> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 is= olate_huge_page(page, pagelist); >> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 er= r =3D 1; >> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 } >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (PageHead(page)) >> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 er= r =3D isolate_huge_page(page, pagelist) ? 1 : -EBUSY; >=20 > Could you elaborate on which case the huge page isolation can be failed= in this case? Or you met a real problem? Cause now we've got this head h= uge page refcnt, I can not see why we'll fail to isolate this huge page. IIUC, this could happen when hugepage is under migration which cleared HP= ageMigratable. Page refcnt cannot prevent isolate_huge_page from happening. Or am I miss something? Many thanks. > .