From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot1-f69.google.com (mail-ot1-f69.google.com [209.85.210.69]) by kanga.kvack.org (Postfix) with ESMTP id 83C588E0001 for ; Sun, 30 Sep 2018 01:46:53 -0400 (EDT) Received: by mail-ot1-f69.google.com with SMTP id k18-v6so11803802otl.16 for ; Sat, 29 Sep 2018 22:46:53 -0700 (PDT) Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com. [148.163.156.1]) by mx.google.com with ESMTPS id n15-v6si771461otb.212.2018.09.29.22.46.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 29 Sep 2018 22:46:52 -0700 (PDT) Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w8U5hbkK096829 for ; Sun, 30 Sep 2018 01:46:51 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 2mtpc036x6-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Sun, 30 Sep 2018 01:46:51 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sun, 30 Sep 2018 06:46:49 +0100 From: Daniel Black Subject: [PATCH] mm: madvise(MADV_DODUMP) allow hugetlbfs pages Date: Sun, 30 Sep 2018 15:46:29 +1000 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <20180930054629.29150-1-daniel@linux.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, mike.kravetz@oracle.com, khlebnikov@openvz.org Cc: Daniel Black Reproducer, assuming 2M of hugetlbfs available: Hugetlbfs mounted, size=2M and option user=testuser # mount | grep ^hugetlbfs hugetlbfs on /dev/hugepages type hugetlbfs (rw,pagesize=2M,user=dan) # sysctl vm.nr_hugepages=1 vm.nr_hugepages = 1 # grep Huge /proc/meminfo AnonHugePages: 0 kB ShmemHugePages: 0 kB HugePages_Total: 1 HugePages_Free: 1 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 2048 kB Code: #include #include #define SIZE 2*1024*1024 int main() { void *ptr; ptr = mmap(NULL, SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_HUGETLB | MAP_ANONYMOUS, -1, 0); madvise(ptr, SIZE, MADV_DONTDUMP); madvise(ptr, SIZE, MADV_DODUMP); } Compile and strace: mmap(NULL, 2097152, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_HUGETLB, -1, 0) = 0x7ff7c9200000 madvise(0x7ff7c9200000, 2097152, MADV_DONTDUMP) = 0 madvise(0x7ff7c9200000, 2097152, MADV_DODUMP) = -1 EINVAL (Invalid argument) hugetlbfs pages have VM_DONTEXPAND in the VmFlags driver pages based on author testing with analysis from Florian Weimer[1]. The inclusion of VM_DONTEXPAND into the VM_SPECIAL defination was a consequence of the large useage of VM_DONTEXPAND in device drivers. A consequence of [2] is that VM_DONTEXPAND marked pages are unable to be marked DODUMP. A user could quite legitimately madvise(MADV_DONTDUMP) their hugetlbfs memory for a while and later request that madvise(MADV_DODUMP) on the same memory. We correct this omission by allowing madvice(MADV_DODUMP) on hugetlbfs pages. [1] https://stackoverflow.com/questions/52548260/madvisedodump-on-the-same-ptr-size-as-a-successful-madvisedontdump-fails-wit [2] commit 0103bd16fb90 ("mm: prepare VM_DONTDUMP for using in drivers") Fixes: 0103bd16fb90 ("mm: prepare VM_DONTDUMP for using in drivers") Reported-by: Kenneth Penza Signed-off-by: Daniel Black Buglink: https://lists.launchpad.net/maria-discuss/msg05245.html Cc: linux-mm@kvack.org Cc: Mike Kravetz Cc: Konstantin Khlebnikov --- mm/madvise.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/madvise.c b/mm/madvise.c index 972a9eaa898b..71d21df2a3f3 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -96,7 +96,7 @@ static long madvise_behavior(struct vm_area_struct *vma, new_flags |= VM_DONTDUMP; break; case MADV_DODUMP: - if (new_flags & VM_SPECIAL) { + if (!is_vm_hugetlb_page(vma) && new_flags & VM_SPECIAL) { error = -EINVAL; goto out; } -- 2.19.0