Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:43624 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725749AbeLAJVL (ORCPT ); Sat, 1 Dec 2018 04:21:11 -0500 Date: Fri, 30 Nov 2018 14:10:25 -0800 From: akpm@linux-foundation.org To: willy@infradead.org, stable@vger.kernel.org, kirill.shutemov@linux.intel.com, khlebnikov@yandex-team.ru, jglisse@redhat.com, hughd@google.com, akpm@linux-foundation.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 24/31] mm/khugepaged: collapse_shmem() stop if punched or truncated Message-ID: <20181130221025.MkV8Q%akpm@linux-foundation.org> Sender: stable-owner@vger.kernel.org List-ID: From: Hugh Dickins Subject: mm/khugepaged: collapse_shmem() stop if punched or truncated 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. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261522040.2275@eggly.anvils Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages") Signed-off-by: Hugh Dickins Reviewed-by: Matthew Wilcox Cc: Kirill A. Shutemov Cc: Jerome Glisse Cc: Konstantin Khlebnikov Cc: [4.8+] Signed-off-by: Andrew Morton --- mm/khugepaged.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/mm/khugepaged.c~mm-khugepaged-collapse_shmem-stop-if-punched-or-truncated +++ a/mm/khugepaged.c @@ -1359,6 +1359,17 @@ static void collapse_shmem(struct mm_str 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; _