From nobody Sat Feb 7 08:58:27 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9DA68C41513 for ; Tue, 8 Aug 2023 02:11:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230263AbjHHCLb (ORCPT ); Mon, 7 Aug 2023 22:11:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229566AbjHHCL3 (ORCPT ); Mon, 7 Aug 2023 22:11:29 -0400 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C6ED19B6; Mon, 7 Aug 2023 19:11:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1691460682; x=1722996682; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=d3VIX2xY+fu1wWsahOfoN14pobtO1cM2MgEWqpBvgLY=; b=EuJd4qa0AAArhVMsFAlVuljUHzrNuN+NCuFOvd/FratfgL2JETvU6eCh qg6KhSCb58AqZmPXhmlnGTLUklrJP7iYSWSXQYEQRj7TcTSSk+e0wJc+m JURZuL/L5ni+vhYi93jQ0OaAWfp8hWPV15Xe0MPextHEwx2/gBdsKQHPx 12/mcxBQm0bm7Olx+egeufVxqoqMDaxF/ysXGR2cqJc/UB5n5PAPL8Hvp iQzc2W1QdyXnuBwG/qtj/XSzk3PlTQcOZVp0R3aZ0IrVRgu1tzPhbFvzG dsZRTrN9URLfshzRnuKIzObcL+fm3PdBJpkYAg1HUJIQWN7+NgtF1ONx1 A==; X-IronPort-AV: E=McAfee;i="6600,9927,10795"; a="373453596" X-IronPort-AV: E=Sophos;i="6.01,263,1684825200"; d="scan'208";a="373453596" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Aug 2023 19:11:21 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10795"; a="977689411" X-IronPort-AV: E=Sophos;i="6.01,263,1684825200"; d="scan'208";a="977689411" Received: from fyin-dev.sh.intel.com ([10.239.159.32]) by fmsmga006.fm.intel.com with ESMTP; 07 Aug 2023 19:11:18 -0700 From: Yin Fengwei To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, akpm@linux-foundation.org, willy@infradead.org, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, minchan@kernel.org, yuzhao@google.com, david@redhat.com, ryan.roberts@arm.com, shy828301@gmail.com Cc: fengwei.yin@intel.com Subject: [PATCH v2 3/3] madvise:madvise_free_pte_range(): don't use mapcount() against large folio for sharing check Date: Tue, 8 Aug 2023 10:09:17 +0800 Message-Id: <20230808020917.2230692-4-fengwei.yin@intel.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230808020917.2230692-1-fengwei.yin@intel.com> References: <20230808020917.2230692-1-fengwei.yin@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Commit 98b211d6415f ("madvise: convert madvise_free_pte_range() to use a folio") replaced the page_mapcount() with folio_mapcount() to check whether the folio is shared by other mapping. It's not correct for large folios. folio_mapcount() returns the total mapcount of large folio which is not suitable to detect whether the folio is shared. Use folio_estimated_sharers() which returns a estimated number of shares. That means it's not 100% correct. It should be OK for madvise case here. User-visible effects is that the THP is skipped when user call madvise. But the correct behavior is THP should be split and processed then. NOTE: this change is a temporary fix to reduce the user-visible effects before the long term fix from David is ready. Fixes: 98b211d6415f ("madvise: convert madvise_free_pte_range() to use a fo= lio") Cc: stable@vger.kernel.org Signed-off-by: Yin Fengwei Reviewed-by: Yu Zhao Reviewed-by: Ryan Roberts --- mm/madvise.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 49af35e2d99a..4dded5d27e7e 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -683,7 +683,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned = long addr, if (folio_test_large(folio)) { int err; =20 - if (folio_mapcount(folio) !=3D 1) + if (folio_estimated_sharers(folio) !=3D 1) break; if (!folio_trylock(folio)) break; --=20 2.39.2