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 089D2C25B0E for ; Wed, 17 Aug 2022 00:58:43 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 848878D0002; Tue, 16 Aug 2022 20:58:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7CFFA8D0001; Tue, 16 Aug 2022 20:58:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 670438D0002; Tue, 16 Aug 2022 20:58:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 540808D0001 for ; Tue, 16 Aug 2022 20:58:42 -0400 (EDT) Received: from smtpin25.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 29D1A1C6C4F for ; 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x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=wDEQ1GWA; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660697921; a=rsa-sha256; cv=none; b=uqkXJG3kFwa/zrOupKmli2DSGF2b4Wqaoy13HT6O2sGSbLzCMEzo1t6LwWF7tMTpaIwvoL B6VbT94RaMXLw7aX7mG3LR+L908KILexhkBln9dYblNnBDn4WjkWotd9vWMhKUW2A5COEO HboOQy4sfUzUhVq6g5KQplAXoECdo1g= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660697921; h=from:from:sender: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:dkim-signature; bh=sYUAWHxWef/8EacrFTI60i1PrXP7loNsfFOq9bMs+2g=; b=wNQh6qClpFt2AQfm2csK9QXS4gRaQipasEv93Tu5aMKcLiG5sk/DTiU2rZpV0vleXbHnlf 0oV/A3nnShoNwA7iOi2zQxUYqde4lrggNUeOooVRNN8cmuOx7UC/gRDwakcbusylbkW++G mDnG+ZqwLnPVYVswQXG0mRe7Pw912C4= X-Stat-Signature: 1smbn9om4yasi4qmqqyohews8mn75tfy X-Rspamd-Queue-Id: A787918004B X-Rspamd-Server: rspam08 Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=wDEQ1GWA; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspam-User: X-HE-Tag: 1660697921-297328 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 Tue, 16 Aug 2022 10:21:00 +0800 Haiyue Wang wrote: > Not all huge page APIs support FOLL_GET option, so move_pages() syscall > will fail to get the page node information for some huge pages. > > Like x86 on linux 5.19 with 1GB huge page API follow_huge_pud(), it will > return NULL page for FOLL_GET when calling move_pages() syscall with the > NULL 'nodes' parameter, the 'status' parameter has '-2' error in array. > > Note: follow_huge_pud() now supports FOLL_GET in linux 6.0. > Link: https://lore.kernel.org/all/20220714042420.1847125-3-naoya.horiguchi@linux.dev > > But these huge page APIs don't support FOLL_GET: > 1. follow_huge_pud() in arch/s390/mm/hugetlbpage.c Let's tell the s390 maintainers. > 2. follow_huge_addr() in arch/ia64/mm/hugetlbpage.c > It will cause WARN_ON_ONCE for FOLL_GET. ia64 doesn't have maintainers :( Can we come up with something local to arch/ia64 for this? > 3. follow_huge_pgd() in mm/hugetlb.c Hi, Mike. > This is an temporary solution to mitigate the side effect of the race > condition fix by calling follow_page() with FOLL_GET set for huge pages. > > After supporting follow huge page by FOLL_GET is done, this fix can be > reverted safely. > > ... > > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1848,6 +1848,7 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, > > for (i = 0; i < nr_pages; i++) { > unsigned long addr = (unsigned long)(*pages); > + unsigned int foll_flags = FOLL_DUMP; > struct vm_area_struct *vma; > struct page *page; > int err = -EFAULT; > @@ -1856,8 +1857,12 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, > if (!vma) > goto set_status; > > + /* Not all huge page follow APIs support 'FOLL_GET' */ > + if (!is_vm_hugetlb_page(vma)) > + foll_flags |= FOLL_GET; > + > /* FOLL_DUMP to ignore special (like zero) pages */ > - page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); > + page = follow_page(vma, addr, foll_flags); > > err = PTR_ERR(page); > if (IS_ERR(page)) > @@ -1865,7 +1870,8 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, > > if (page && !is_zone_device_page(page)) { > err = page_to_nid(page); > - put_page(page); > + if (foll_flags & FOLL_GET) > + put_page(page); > } else { > err = -ENOENT; > } I would be better to fix this for real at those three client code sites?