after install libguestfs_xfs, all results are: [using guestfish] guestfish -N fs:xfs -m /dev/sda1 statvfs / bsize: 4096 frsize: 4096 blocks: 24713 bfree: 23391 bavail: 23391 files: 51136 ffree: 51133 favail: 51133 fsid: 2049 flag: 4096 namemax: 255 [using virt-rescure] virt-rescue -a test1.img><rescue> mount /dev/sda1 /sysroot ><rescue> stat -f /sysrootFile: "/sysroot" ID: 80100000000 Namelen: 255 Type: xfs Block size: 4096 Fundamental block size: 4096 Blocks: Total: 24713 Free: 23391 Available: 23391 Inodes: Total: 51136 Free: 51133 the free numbers are the same. but the "virt-df" output is not changed. Thanks, Chen 在 2018-01-07 20:22:28，"Richard W.M. Jones" <rjones@redhat.com> 写道：>On Sun, Jan 07, 2018 at 08:11:58PM +0800, 陈帆 wrote: >> Sorry for the late reply. when I used your method to execute command: >> $guestfish -N fs:xfs -m /dev/sda1 statvfs / >> libguestfs: error: mkfs: xfs: /dev/sda1: mkfs.xfs: No such file or directory >> guestfish: error creating prepared disk image 'fs:xfs' on 'test1.img': failed to create filesystem (xfs): mkfs: xfs: /dev/sda1: mkfs.xfs: No such file or directory > >You need to install ‘libguestfs-xfs’. > >Rich. > >-- >Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones >Read my programming and virtualization blog: http://rwmj.wordpress.com >virt-p2v converts physical machines to virtual machines. Boot with a >live CD or over the network (PXE) and turn machines into KVM guests. >http://libguestfs.org/virt-v2v
Richard W.M. Jones
2018-Jan-08 08:23 UTC
Re: [Libguestfs] virtdf outputs on host differs from df in guest
There are some strange things going on with the kernel XFS driver.
Opening a filesystem for write or read-only makes a difference to the
stats returned.
With bit-for-bit identical filesystems:
><rescue> mount /dev/sda1 /sysroot
><rescue> stat -f /sysroot
File: "/sysroot"
ID: 80100000000 Namelen: 255 Type: xfs
Block size: 4096 Fundamental block size: 4096
Blocks: Total: 24713 Free: 23347 Available: 23347
Inodes: Total: 51136 Free: 51133
vs:
><rescue> mount -o ro /dev/sda1 /sysroot
><rescue> stat -f /sysroot
File: "/sysroot"
ID: 80100000000 Namelen: 255 Type: xfs
Block size: 4096 Fundamental block size: 4096
Blocks: Total: 24713 Free: 24653 Available: 24653
Inodes: Total: 51136 Free: 51133
virt-df always uses the ‘-o ro’ option.
Despite this virt-df itself is working fine:
$ virt-df -a test1.img
Filesystem 1K-blocks Used Available Use%
test1.img:/dev/sda1 98852 240 98612 1%
Using the calculations from here:
https://github.com/libguestfs/libguestfs/blob/ab0a3e0276656965021413194380ae602c05513d/df/output.c#L126-L136
blocks * bsize / 1024 = 24713 * 4096 / 1024 = 98852
(blocks - bfree) * bsize / 1024 = (24713-24653) * 4096 / 1024 = 240
bavail * bsize / 1024 = 24653 * 4096 / 1024 = 98612
So everything appears to be working fine, besides possibly odd stuff
going on in the kernel XFS driver.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
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Richard W.M. Jones
2018-Jan-08 12:09 UTC
Re: [Libguestfs] virtdf outputs on host differs from df in guest
The answer is attached. In summary it's not a bug in virt-df, nor df, nor the kernel. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/ --qyHYMwAXsHLOQihY Content-Type: message/rfc822 Content-Disposition: inline Content-Transfer-Encoding: 8bit Return-Path: david@fromorbit.com X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on rhmail.home.annexia.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_LOW, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 Received: from mail.corp.redhat.com [10.4.203.66] by rhmail.home.annexia.org with IMAP (fetchmail-6.3.17) for <rjones@localhost> (single-drop); Mon, 08 Jan 2018 11:43:47 +0000 (GMT) Received: from zmta01.collab.prod.int.phx2.redhat.com (LHLO zmta01.collab.prod.int.phx2.redhat.com) (10.5.81.8) by zmail20.collab.prod.int.phx2.redhat.com with LMTP; Mon, 8 Jan 2018 06:43:14 -0500 (EST) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) by zmta01.collab.prod.int.phx2.redhat.com (Postfix) with ESMTP id 8C22E186679 for <rjones@mail.corp.redhat.com>; Mon, 8 Jan 2018 06:43:14 -0500 (EST) Received: by smtp.corp.redhat.com (Postfix) id 883B75C25E; Mon, 8 Jan 2018 11:43:14 +0000 (UTC) Delivered-To: rjones@redhat.com Received: from mx1.redhat.com (ext-mx05.extmail.prod.ext.phx2.redhat.com [10.5.110.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 823DD5E1A0 for <rjones@redhat.com>; Mon, 8 Jan 2018 11:43:14 +0000 (UTC) Received: from ipmail03.adl2.internode.on.net (ipmail03.adl2.internode.on.net [150.101.137.141]) by mx1.redhat.com (Postfix) with ESMTP id 27C7631A334 for <rjones@redhat.com>; Mon, 8 Jan 2018 11:43:12 +0000 (UTC) Received: from ppp59-167-129-252.static.internode.on.net (HELO dastard) ([59.167.129.252]) by ipmail03.adl2.internode.on.net with ESMTP; 08 Jan 2018 22:13:09 +1030 Received: from dave by dastard with local (Exim 4.80) (envelope-from <david@fromorbit.com>) id 1eYVpZ-0006Nj-61; Mon, 08 Jan 2018 22:43:05 +1100 Date: Mon, 8 Jan 2018 22:43:05 +1100 From: Dave Chinner <david@fromorbit.com> To: "Richard W.M. Jones" <rjones@redhat.com> Cc: linux-xfs@vger.kernel.org Subject: Re: statfs b_avail & b_free different if the filesystem is mounted readonly Message-ID: <20180108114305.GA16421@dastard> References: <20180108084450.GU2787@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180108084450.GU2787@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Greylist: Sender passed SPF test, Sender IP whitelisted by DNSRBL, ACL 207 matched, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 08 Jan 2018 11:43:12 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Mon, 08 Jan 2018 11:43:12 +0000 (UTC) for IP:'150.101.137.141' DOMAIN:'ipmail03.adl2.internode.on.net' HELO:'ipmail03.adl2.internode.on.net' FROM:'david@fromorbit.com' RCPT:'' X-RedHat-Spam-Score: -0.72 (RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL) 150.101.137.141 ipmail03.adl2.internode.on.net 150.101.137.141 ipmail03.adl2.internode.on.net <david@fromorbit.com> X-Scanned-By: MIMEDefang 2.78 on 10.5.110.29 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 On Mon, Jan 08, 2018 at 08:44:50AM +0000, Richard W.M. Jones wrote:> We had a question[1] posed by a libguestfs user who wondered why the > output of virt-df and df differ for an XFS filesystem. After > looking into the details it turns out that the statfs(2) system call > gives slightly different answers if the filesystem is mounted > read-write vs read-only. > > ><rescue> mount /dev/sda1 /sysroot > ><rescue> stat -f /sysroot > File: "/sysroot" > ID: 80100000000 Namelen: 255 Type: xfs > Block size: 4096 Fundamental block size: 4096 > Blocks: Total: 24713 Free: 23347 Available: 23347 > Inodes: Total: 51136 Free: 51133 > > vs: > > ><rescue> mount -o ro /dev/sda1 /sysroot > ><rescue> stat -f /sysroot > File: "/sysroot" > ID: 80100000000 Namelen: 255 Type: xfs > Block size: 4096 Fundamental block size: 4096 > Blocks: Total: 24713 Free: 24653 Available: 24653 > Inodes: Total: 51136 Free: 51133 > > virt-df uses -o ro and in the df case the user had the > filesystem mounted read-write, hence different results. > > I looked into the kernel code and it's all pretty complicated. I > couldn't see exactly where this difference could come from.Pretty simple when you know what to look for :P This is off the top of my head, but the difference is mostly going to be the ENOSPC reserve pool (xfs_reserve_blocks(), IIRC). it's size is min(%5 total, 8192) blocks, and it's not reserved on a read-only mount because it's only required for certain modifications at ENOSPC that can't be reserved ahead of time (e.g. btree blocks for an extent split during unwritten extent conversion at ENOSPC). The numbers above will be slightly more than 5%, because total blocks reported in fsstat doesn't include things like th space used by the journal, whereas the reserve pool sizing just works from raw sizes in the on-disk superblock. So total fs size is at least 24713 blocks. 5% of that is 1235.6 blocks. The difference in free blocks is 24653 - 23347 = 1306 blocks. It's right in the ballpark I'd expect....> My questions are: Is there a reason for this difference, and is one of > the answers more correct than the other?Yes, there's a reason. No, both are correct. :P Cheers, Dave. -- Dave Chinner david@fromorbit.com --qyHYMwAXsHLOQihY--
Chen Fan
2018-Jan-08 12:21 UTC
Re: [Libguestfs] virtdf outputs on host differs from df in guest
thank you very much for your help :). Thanks, Chen On 2018年01月08日 20:09, Richard W.M. Jones wrote:> The answer is attached. In summary it's not a bug in virt-df, > nor df, nor the kernel. > > Rich. >