From patchwork Wed Sep 21 22:10:43 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zach O'Keefe X-Patchwork-Id: 12984245 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 46169C6FA8E for ; Wed, 21 Sep 2022 22:11:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CDB226B0071; Wed, 21 Sep 2022 18:10:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C8B3B6B0072; Wed, 21 Sep 2022 18:10:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B53FA6B0073; Wed, 21 Sep 2022 18:10:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id A58D96B0071 for ; 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bh=keAwuVCNVa6w7Ik/A0l5oKvw/3mmejPS+N82b9fiUXk=; b=Zi66j1zS4+aVEEn39+CjUMuXYqu8SHDqDfNP/osPoTj9CAgWvyVscWQtr4x8GywcJEotyb Tj2yi1caaebMUre1dp3oBTQNdkeHcyCJnRCdPCn+l2EOFG7VxS3Dh9AWp5EBlIP82gFQb1 CkfHOzp5SREFs7+POFbp+wj1OLXr33w= X-Stat-Signature: 1bar7hjjfgmjbup3nqqb3k37nidseg1u X-Rspamd-Queue-Id: 379642000D Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b="A/m9vHmr"; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf31.hostedemail.com: domain of 38osrYwcKCNcSHD77879HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--zokeefe.bounces.google.com designates 209.85.216.74 as permitted sender) smtp.mailfrom=38osrYwcKCNcSHD77879HH9E7.5HFEBGNQ-FFDO35D.HK9@flex--zokeefe.bounces.google.com X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1663798259-92509 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: By the time we lock a page in collapse_pte_mapped_thp(), the page mapped by the address pushed onto the slot's .pte_mapped_thp[] array might have changed arbitrarily since we last looked at it. We revalidate that the page is still the head of a compound page, but we don't revalidate if the compound page is of order HPAGE_PMD_ORDER before applying rmap and page table updates. Since the kernel now supports large folios of arbitrary order, and since replacing page's pte mappings by a pmd mapping only makes sense for compound pages of order HPAGE_PMD_ORDER, revalidate that the compound order is indeed of order HPAGE_PMD_ORDER before proceeding. Suggested-by: Yang Shi Signed-off-by: Zach O'Keefe --- Andrew, could you please take this into mm-unstable as a prerequisite patch for the "mm: add file/shmem support to MADV_COLLAPSE" series? Thank you. mm/khugepaged.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 122cb72435e3..30f35d646f11 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1448,6 +1448,11 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr, goto drop_hpage; } + if (compound_order(hpage) != HPAGE_PMD_ORDER) { + result = SCAN_PAGE_COMPOUND; + goto drop_hpage; + } + result = find_pmd_or_thp_or_none(mm, haddr, &pmd); switch (result) { case SCAN_SUCCEED: