From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by kanga.kvack.org (Postfix) with ESMTP id 730786B445D for ; Mon, 26 Nov 2018 18:23:40 -0500 (EST) Received: by mail-pg1-f200.google.com with SMTP id s27so8827838pgm.4 for ; Mon, 26 Nov 2018 15:23:40 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id r12sor2512417plo.58.2018.11.26.15.23.39 for (Google Transport Security); Mon, 26 Nov 2018 15:23:39 -0800 (PST) Date: Mon, 26 Nov 2018 15:23:37 -0800 (PST) From: Hugh Dickins Subject: [PATCH 04/10] mm/khugepaged: collapse_shmem() stop if punched or truncated In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: "Kirill A. Shutemov" , "Kirill A. Shutemov" , Matthew Wilcox , linux-mm@kvack.org Huge tmpfs testing showed that although collapse_shmem() recognizes a concurrently truncated or hole-punched page correctly, its handling of holes was liable to refill an emptied extent. Add check to stop that. Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Hugh Dickins Cc: Kirill A. Shutemov Cc: stable@vger.kernel.org # 4.8+ --- mm/khugepaged.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index c13625c1ad5e..2070c316f06e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1359,6 +1359,17 @@ static void collapse_shmem(struct mm_struct *mm, VM_BUG_ON(index != xas.xa_index); if (!page) { + /* + * Stop if extent has been truncated or hole-punched, + * and is now completely empty. + */ + if (index == start) { + if (!xas_next_entry(&xas, end - 1)) { + result = SCAN_TRUNCATED; + break; + } + xas_set(&xas, index); + } if (!shmem_charge(mapping->host, 1)) { result = SCAN_FAIL; break; -- 2.20.0.rc0.387.gc7a69e6b6c-goog