From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 070E66B029A for ; Wed, 22 Nov 2017 09:44:04 -0500 (EST) Received: by mail-pg0-f70.google.com with SMTP id 192so16301539pgd.18 for ; Wed, 22 Nov 2017 06:44:03 -0800 (PST) Received: from NAM01-BY2-obe.outbound.protection.outlook.com (mail-by2nam01on0137.outbound.protection.outlook.com. [104.47.34.137]) by mx.google.com with ESMTPS id m3si13596513pgs.471.2017.11.22.06.44.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 22 Nov 2017 06:44:02 -0800 (PST) Message-ID: <5A158D22.3040609@cs.rutgers.edu> Date: Wed, 22 Nov 2017 09:43:46 -0500 From: Zi Yan MIME-Version: 1.0 Subject: Re: [PATCH] mm: migrate: fix an incorrect call of prep_transhuge_page() References: <20171121021855.50525-1-zi.yan@sent.com> <20171122085416.ycrvahu2bznlx37s@dhcp22.suse.cz> <20171122134059.fmyambktkel4e3zq@dhcp22.suse.cz> In-Reply-To: <20171122134059.fmyambktkel4e3zq@dhcp22.suse.cz> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enig97BB13ED2DB5359A2AEE3BB8" Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Zi Yan , Naoya Horiguchi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrea Reale , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , stable@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig97BB13ED2DB5359A2AEE3BB8 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Michal Hocko wrote: > On Wed 22-11-17 09:54:16, Michal Hocko wrote: >> On Mon 20-11-17 21:18:55, Zi Yan wrote: > [...] >>> diff --git a/include/linux/migrate.h b/include/linux/migrate.h >>> index 895ec0c4942e..a2246cf670ba 100644 >>> --- a/include/linux/migrate.h >>> +++ b/include/linux/migrate.h >>> @@ -54,7 +54,7 @@ static inline struct page *new_page_nodemask(struct= page *page, >>> new_page =3D __alloc_pages_nodemask(gfp_mask, order, >>> preferred_nid, nodemask); >>> =20 >>> - if (new_page && PageTransHuge(page)) >>> + if (new_page && PageTransHuge(new_page)) >>> prep_transhuge_page(new_page); >> I would keep the two checks consistent. But that leads to a more >> interesting question. new_page_nodemask does >> >> if (thp_migration_supported() && PageTransHuge(page)) { >> order =3D HPAGE_PMD_ORDER; >> gfp_mask |=3D GFP_TRANSHUGE; >> } >=20 > And one more question/note. Why do we need thp_migration_supported > in the first place? 9c670ea37947 ("mm: thp: introduce > CONFIG_ARCH_ENABLE_THP_MIGRATION") says > : Introduce CONFIG_ARCH_ENABLE_THP_MIGRATION to limit thp migration > : functionality to x86_64, which should be safer at the first step. >=20 > but why is unsafe to enable the feature on other arches which support > THP? Is there any plan to do the next step and remove this config > option? Because different architectures have their own way of specifying a swap entry. This means, to support THP migration, each architecture needs to add its own __pmd_to_swp_entry() and __swp_entry_to_pmd(), which are used for arch-independent pmd_to_swp_entry() and swp_entry_to_pmd(). We need this CONFIG_ARCH_ENABLE_THP_MIGRATION before archs that support THP add code for pmd swap entry. --=20 Best Regards, Yan Zi --------------enig97BB13ED2DB5359A2AEE3BB8 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBCAAGBQJaFY05AAoJEEGLLxGcTqbMgIMH+gL5yfMn4qjZ61tXon+Pd5SZ 2V6ZBz6hHrUr0m/BUleXwaKs6Y6t+9V8VjOz/fEkWLRDxd/IwPKiiJNHJcwjl1Wl l2kM8gGyhiK/zynZM0l+m70yvxCgKwn5alVbUHutokDWYsAW7w4maghFBYdlnojh 2DwdPcqt5AQkFU9MHFvoWKgYSGlCgQq0vVYbleZ91EbokU+rrsvTig94QuU5qH/V Cqdgxrof6U5c0yupjYg+yrt3+W/pfe4IRbVzjHKv7QkeWBq8fUSKiOEM/WolGZ1a 2el2/dasgXJGtyf9OoKZ4mI6T/DUKEn4fx4W80zSLKpcAxz5e7m2HQgKPKQ3c1w= =2We7 -----END PGP SIGNATURE----- --------------enig97BB13ED2DB5359A2AEE3BB8-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org