From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f43.google.com (mail-oi0-f43.google.com [209.85.218.43]) by kanga.kvack.org (Postfix) with ESMTP id 829AA6B0038 for ; Wed, 12 Aug 2015 04:57:01 -0400 (EDT) Received: by oip136 with SMTP id 136so5652481oip.1 for ; Wed, 12 Aug 2015 01:57:01 -0700 (PDT) Received: from tyo201.gate.nec.co.jp (TYO201.gate.nec.co.jp. [210.143.35.51]) by mx.google.com with ESMTPS id m71si4013905oig.104.2015.08.12.01.57.00 for (version=TLS1 cipher=RC4-SHA bits=128/128); Wed, 12 Aug 2015 01:57:00 -0700 (PDT) From: Naoya Horiguchi Subject: Re: [PATCH v2 5/5] mm/hwpoison: replace most of put_page in memory error handling by put_hwpoison_page Date: Wed, 12 Aug 2015 08:55:26 +0000 Message-ID: <20150812085525.GD32192@hori1.linux.bs1.fc.nec.co.jp> References: <1439206103-86829-1-git-send-email-wanpeng.li@hotmail.com> In-Reply-To: Content-Language: ja-JP Content-Type: text/plain; charset="iso-2022-jp" Content-ID: <843CC0B960D5994BBFBAE8B5AC12A0CB@gisp.nec.co.jp> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Wanpeng Li Cc: Andrew Morton , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" On Mon, Aug 10, 2015 at 07:28:23PM +0800, Wanpeng Li wrote: > Replace most of put_page in memory error handling by put_hwpoison_page, > except the ones at the front of soft_offline_page since the page maybe > THP page and the get refcount in madvise_hwpoison is against the single > 4KB page instead of the logic in get_hwpoison_page. > > Signed-off-by: Wanpeng Li # Sorry for my late response. If I read correctly, get_user_pages_fast() (called by madvise_hwpoison) for a THP tail page takes a refcount from each of head and tail page. gup_huge_pmd() does this in the fast path, and get_page_foll() does this in the slow path (maybe via the following code path) get_user_pages_unlocked __get_user_pages_unlocked __get_user_pages_locked __get_user_pages follow_page_mask follow_trans_huge_pmd (with FOLL_GET set) get_page_foll So this should be equivalent to what get_hwpoison_page() does for thp pages with regard to refcounting. And I'm expecting that a refcount taken by get_hwpoison_page() is released by put_hwpoison_page() even if the page's status is changed during error handling (the typical (or only?) case is successful thp split.) So I think you can apply put_hwpoison_page() for 3 more callsites in mm/memory-failure.c. - MF_MSG_POISONED_HUGE case - "soft offline: %#lx page already poisoned" case (you mentioned above) - "soft offline: %#lx: failed to split THP" case (you mentioned above) Thanks, Naoya Horiguchi= -- 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