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[209.132.183.28]) by mx.google.com with ESMTPS id v74si1645330qkl.213.2019.03.11.02.55.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Mar 2019 02:55:51 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3832CC057F3F; Mon, 11 Mar 2019 09:55:50 +0000 (UTC) Received: from [10.36.117.207] (ovpn-117-207.ams2.redhat.com [10.36.117.207]) by smtp.corp.redhat.com (Postfix) with ESMTP id CCD605D706; Mon, 11 Mar 2019 09:55:41 +0000 (UTC) Subject: Re: [PATCH v2 3/8] kexec: export PG_offline to VMCOREINFO To: Dave Young Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, devel@linuxdriverproject.org, linux-fsdevel@vger.kernel.org, linux-pm@vger.kernel.org, xen-devel@lists.xenproject.org, kexec-ml , pv-drivers@vmware.com, Andrew Morton , "Kirill A. Shutemov" , Baoquan He , Omar Sandoval , Arnd Bergmann , Matthew Wilcox , Michal Hocko , "Michael S. Tsirkin" , Lianbo Jiang , Borislav Petkov , Kazuhito Hagio References: <20181122100627.5189-1-david@redhat.com> <20181122100627.5189-4-david@redhat.com> <20190311090402.GA12071@dhcp-128-65.nay.redhat.com> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwX4EEwECACgFAljj9eoCGwMFCQlmAYAGCwkI BwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEE3eEPcA/4Na5IIP/3T/FIQMxIfNzZshIq687qgG 8UbspuE/YSUDdv7r5szYTK6KPTlqN8NAcSfheywbuYD9A4ZeSBWD3/NAVUdrCaRP2IvFyELj xoMvfJccbq45BxzgEspg/bVahNbyuBpLBVjVWwRtFCUEXkyazksSv8pdTMAs9IucChvFmmq3 jJ2vlaz9lYt/lxN246fIVceckPMiUveimngvXZw21VOAhfQ+/sofXF8JCFv2mFcBDoa7eYob s0FLpmqFaeNRHAlzMWgSsP80qx5nWWEvRLdKWi533N2vC/EyunN3HcBwVrXH4hxRBMco3jvM m8VKLKao9wKj82qSivUnkPIwsAGNPdFoPbgghCQiBjBe6A75Z2xHFrzo7t1jg7nQfIyNC7ez MZBJ59sqA9EDMEJPlLNIeJmqslXPjmMFnE7Mby/+335WJYDulsRybN+W5rLT5aMvhC6x6POK z55fMNKrMASCzBJum2Fwjf/VnuGRYkhKCqqZ8gJ3OvmR50tInDV2jZ1DQgc3i550T5JDpToh dPBxZocIhzg+MBSRDXcJmHOx/7nQm3iQ6iLuwmXsRC6f5FbFefk9EjuTKcLMvBsEx+2DEx0E UnmJ4hVg7u1PQ+2Oy+Lh/opK/BDiqlQ8Pz2jiXv5xkECvr/3Sv59hlOCZMOaiLTTjtOIU7Tq 7ut6OL64oAq+zsFNBFXLn5EBEADn1959INH2cwYJv0tsxf5MUCghCj/CA/lc/LMthqQ773ga uB9mN+F1rE9cyyXb6jyOGn+GUjMbnq1o121Vm0+neKHUCBtHyseBfDXHA6m4B3mUTWo13nid 0e4AM71r0DS8+KYh6zvweLX/LL5kQS9GQeT+QNroXcC1NzWbitts6TZ+IrPOwT1hfB4WNC+X 2n4AzDqp3+ILiVST2DT4VBc11Gz6jijpC/KI5Al8ZDhRwG47LUiuQmt3yqrmN63V9wzaPhC+ xbwIsNZlLUvuRnmBPkTJwwrFRZvwu5GPHNndBjVpAfaSTOfppyKBTccu2AXJXWAE1Xjh6GOC 8mlFjZwLxWFqdPHR1n2aPVgoiTLk34LR/bXO+e0GpzFXT7enwyvFFFyAS0Nk1q/7EChPcbRb hJqEBpRNZemxmg55zC3GLvgLKd5A09MOM2BrMea+l0FUR+PuTenh2YmnmLRTro6eZ/qYwWkC u8FFIw4pT0OUDMyLgi+GI1aMpVogTZJ70FgV0pUAlpmrzk/bLbRkF3TwgucpyPtcpmQtTkWS gDS50QG9DR/1As3LLLcNkwJBZzBG6PWbvcOyrwMQUF1nl4SSPV0LLH63+BrrHasfJzxKXzqg rW28CTAE2x8qi7e/6M/+XXhrsMYG+uaViM7n2je3qKe7ofum3s4vq7oFCPsOgwARAQABwsFl BBgBAgAPBQJVy5+RAhsMBQkJZgGAAAoJEE3eEPcA/4NagOsP/jPoIBb/iXVbM+fmSHOjEshl KMwEl/m5iLj3iHnHPVLBUWrXPdS7iQijJA/VLxjnFknhaS60hkUNWexDMxVVP/6lbOrs4bDZ NEWDMktAeqJaFtxackPszlcpRVkAs6Msn9tu8hlvB517pyUgvuD7ZS9gGOMmYwFQDyytpepo YApVV00P0u3AaE0Cj/o71STqGJKZxcVhPaZ+LR+UCBZOyKfEyq+ZN311VpOJZ1IvTExf+S/5 lqnciDtbO3I4Wq0ArLX1gs1q1XlXLaVaA3yVqeC8E7kOchDNinD3hJS4OX0e1gdsx/e6COvy qNg5aL5n0Kl4fcVqM0LdIhsubVs4eiNCa5XMSYpXmVi3HAuFyg9dN+x8thSwI836FoMASwOl C7tHsTjnSGufB+D7F7ZBT61BffNBBIm1KdMxcxqLUVXpBQHHlGkbwI+3Ye+nE6HmZH7IwLwV W+Ajl7oYF+jeKaH4DZFtgLYGLtZ1LDwKPjX7VAsa4Yx7S5+EBAaZGxK510MjIx6SGrZWBrrV TEvdV00F2MnQoeXKzD7O4WFbL55hhyGgfWTHwZ457iN9SgYi1JLPqWkZB0JRXIEtjd4JEQcx +8Umfre0Xt4713VxMygW0PnQt5aSQdMD58jHFxTk092mU+yIHj5LeYgvwSgZN4airXk5yRXl SE+xAvmumFBY Organization: Red Hat GmbH Message-ID: Date: Mon, 11 Mar 2019 10:55:41 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190311090402.GA12071@dhcp-128-65.nay.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 11 Mar 2019 09:55:50 +0000 (UTC) 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: On 11.03.19 10:04, Dave Young wrote: > Hi David, > On 11/22/18 at 11:06am, David Hildenbrand wrote: >> Right now, pages inflated as part of a balloon driver will be dumped >> by dump tools like makedumpfile. While XEN is able to check in the >> crash kernel whether a certain pfn is actuall backed by memory in the >> hypervisor (see xen_oldmem_pfn_is_ram) and optimize this case, dumps of >> other balloon inflated memory will essentially result in zero pages getting >> allocated by the hypervisor and the dump getting filled with this data. >> >> The allocation and reading of zero pages can directly be avoided if a >> dumping tool could know which pages only contain stale information not to >> be dumped. >> >> We now have PG_offline which can be (and already is by virtio-balloon) >> used for marking pages as logically offline. Follow up patches will >> make use of this flag also in other balloon implementations. >> >> Let's export PG_offline via PAGE_OFFLINE_MAPCOUNT_VALUE, so >> makedumpfile can directly skip pages that are logically offline and the >> content therefore stale. (we export is as a macro to match how it is >> done for PG_buddy. This way it is clearer that this is not actually a flag >> but only a very specific mapcount value to represent page types). >> >> Please note that this is also helpful for a problem we were seeing under >> Hyper-V: Dumping logically offline memory (pages kept fake offline while >> onlining a section via online_page_callback) would under some condicions >> result in a kernel panic when dumping them. >> >> Cc: Andrew Morton >> Cc: Dave Young >> Cc: "Kirill A. Shutemov" >> Cc: Baoquan He >> Cc: Omar Sandoval >> Cc: Arnd Bergmann >> Cc: Matthew Wilcox >> Cc: Michal Hocko >> Cc: "Michael S. Tsirkin" >> Cc: Lianbo Jiang >> Cc: Borislav Petkov >> Cc: Kazuhito Hagio >> Acked-by: Michael S. Tsirkin >> Acked-by: Dave Young >> Signed-off-by: David Hildenbrand >> --- >> kernel/crash_core.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/kernel/crash_core.c b/kernel/crash_core.c >> index 933cb3e45b98..093c9f917ed0 100644 >> --- a/kernel/crash_core.c >> +++ b/kernel/crash_core.c >> @@ -464,6 +464,8 @@ static int __init crash_save_vmcoreinfo_init(void) >> VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE); >> #ifdef CONFIG_HUGETLB_PAGE >> VMCOREINFO_NUMBER(HUGETLB_PAGE_DTOR); >> +#define PAGE_OFFLINE_MAPCOUNT_VALUE (~PG_offline) >> + VMCOREINFO_NUMBER(PAGE_OFFLINE_MAPCOUNT_VALUE); >> #endif >> >> arch_crash_save_vmcoreinfo(); > > The patch has been merged, would you mind to send a documentation patch > for the vmcoreinfo, which is added recently in Documentation/kdump/vmcoreinfo.txt > > A brief description about how this vmcoreinfo field is used is good to > have. > Turns out, it was already documented PG_lru|PG_private|PG_swapcache|PG_swapbacked|PG_slab|PG_hwpoision |PG_head_mask|PAGE_BUDDY_MAPCOUNT_VALUE(~PG_buddy) |PAGE_OFFLINE_MAPCOUNT_VALUE(~PG_offline) ----------------------------------------------------------------- Page attributes. These flags are used to filter various unnecessary for dumping pages. Thanks! > Thanks > Dave > -- Thanks, David / dhildenb