Date:	Mon, 15 Oct 2012 12:32:24 +0000
From:	"Myklebust, Trond" <Trond.Myklebust@...app.com>
To:	Chen Gang <gang.chen@...anux.com>
CC:	Jeff Layton <jlayton@...hat.com>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Bug fix] nfs-client: fix nfs_inode_attrs_need_update for async
 read_done comes during truncating to smaller size

On Mon, 2012-10-15 at 12:52 +0800, Chen Gang wrote:
> 于 2012年10月15日 12:27, Myklebust, Trond 写道:
> > nfs_size_need_update is not about performance. It is a heuristic that is
> > entirely about ensuring correctness when faced with the fact that most
> > Linux filesystems are utterly incapable of reporting with modifications
> > that occur within < 1 second intervals because their mtime/ctime is
> > limited to 1 second resolutions.
> > 
> 
> if truly it was for correctness, why not use "!=" instead of '>' ?

RPC is not ordered. The fact that we get one RPC reply before another
does not mean that the server sent them in that order.

This is doubly true when you use UDP as the transport protocol.

> > Now, what are the conditions of your test setup? The above bug report is
> > meaningless unless it includes a description of what is being exported
> > by the server (including a proper listing of the contents
> > of /etc/exports and /proc/mounts). It should also include a description
> > of the NFS client mount options (see /proc/mounts on the client).
> 
> they are below, if you need additional information, please tell me again.
> 
> for server:
> (nfsx-linux using rsh auto exportfs in cmd line, not in /etc/exports)
> --------------------------------------------------------------------
> root@...p122:~# exportfs
> /tmp/fsx18251.testdir
> 		<world>
> /tmp          	<world>
> root@...p122:~#
> root@...p122:~# cat /etc/exports
> # /etc/exports: the access control list for filesystems which may be
> exported
> #		to NFS clients.  See exports(5).
> #
> # Example for NFSv2 and NFSv3:
> # /srv/homes       hostname1(rw,sync,no_subtree_check)
> hostname2(ro,sync,no_subtree_check)
> #
> # Example for NFSv4:
> # /srv/nfs4        gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check)
> # /srv/nfs4/homes  gss/krb5i(rw,sync,no_subtree_check)
> #
> /tmp *(rw,sync,no_root_squash,no_subtree_check)
> root@...p122:~#
> root@...p122:~# cat /proc/mounts
> rootfs / rootfs rw 0 0
> sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
> proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
> udev /dev devtmpfs rw,relatime,size=1229628k,nr_inodes=189901,mode=755 0 0
> devpts /dev/pts devpts
> rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
> tmpfs /run tmpfs rw,nosuid,relatime,size=516280k,mode=755 0 0
> /dev/disk/by-uuid/e843c57e-98ce-44cc-8e02-6d8e8d8a01b6 / ext4

OK. So the export is part of this ext4 filesystem?

> rw,relatime,errors=remount-ro,data=ordered 0 0
> cgroup /sys/fs/cgroup tmpfs rw,relatime,mode=755 0 0
> cgroup /sys/fs/cgroup/cpuset cgroup rw,relatime,cpuset 0 0
> cgroup /sys/fs/cgroup/cpu cgroup rw,relatime,cpu 0 0
> cgroup /sys/fs/cgroup/cpuacct cgroup rw,relatime,cpuacct 0 0
> cgroup /sys/fs/cgroup/devices cgroup rw,relatime,devices 0 0
> cgroup /sys/fs/cgroup/freezer cgroup rw,relatime,freezer 0 0
> cgroup /sys/fs/cgroup/blkio cgroup rw,relatime,blkio 0 0
> cgroup /sys/fs/cgroup/perf_event cgroup rw,relatime,perf_event 0 0
> none /sys/fs/fuse/connections fusectl rw,relatime 0 0
> none /sys/kernel/debug debugfs rw,relatime 0 0
> none /sys/kernel/security securityfs rw,relatime 0 0
> none /run/lock tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k 0 0
> none /run/shm tmpfs rw,nosuid,nodev,relatime 0 0
> rpc_pipefs /run/rpc_pipefs rpc_pipefs rw,relatime 0 0
> nfsd /proc/fs/nfsd nfsd rw,relatime 0 0
> root@...p122:~#
> -----------------------------------------------------------------------
> 
> for client:
> -----------------------------------------------------------------------
> 
> root@...p159:/opt/ltp/testscripts# cat /proc/mounts
> rootfs / rootfs rw 0 0
> sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
> proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
> udev /dev devtmpfs rw,relatime,size=1103700k,nr_inodes=190392,mode=755 0 0
> devpts /dev/pts devpts
> rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
> tmpfs /run tmpfs rw,nosuid,relatime,size=465908k,mode=755 0 0
> /dev/disk/by-uuid/418ec1f1-ed9d-4cae-9336-6c742accf538 / ext4
> rw,relatime,errors=remount-ro,data=ordered 0 0
> cgroup /sys/fs/cgroup tmpfs rw,relatime,mode=755 0 0
> cgroup /sys/fs/cgroup/cpuset cgroup rw,relatime,cpuset 0 0
> cgroup /sys/fs/cgroup/cpu cgroup rw,relatime,cpu 0 0
> cgroup /sys/fs/cgroup/cpuacct cgroup rw,relatime,cpuacct 0 0
> cgroup /sys/fs/cgroup/devices cgroup rw,relatime,devices 0 0
> cgroup /sys/fs/cgroup/freezer cgroup rw,relatime,freezer 0 0
> cgroup /sys/fs/cgroup/blkio cgroup rw,relatime,blkio 0 0
> cgroup /sys/fs/cgroup/perf_event cgroup rw,relatime,perf_event 0 0
> none /sys/fs/fuse/connections fusectl rw,relatime 0 0
> none /sys/kernel/debug debugfs rw,relatime 0 0
> none /sys/kernel/security securityfs rw,relatime 0 0
> none /run/lock tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k 0 0
> none /run/shm tmpfs rw,nosuid,nodev,relatime 0 0
> rpc_pipefs /run/rpc_pipefs rpc_pipefs rw,relatime 0 0
> nfsd /proc/fs/nfsd nfsd rw,relatime 0 0
> /dev/sda1 /mnt/sda1 ext3
> rw,relatime,errors=continue,user_xattr,acl,barrier=1,data=ordered 0 0
> dhcp122.asianux.net:/tmp/fsx18251.testdir/
> /opt/ltp/testcases/bin/fsx18251 nfs
> rw,relatime,vers=2,rsize=8192,wsize=8192,namlen=255,hard,proto=udp,timeo=11,retrans=3,sec=sys,mountaddr=10.1.0.139,mountvers=1,mountport=39973,mountproto=udp,local_lock=none,addr=10.1.0.139
> 0 0
> root@...p159:/opt/ltp/testscripts#

...and you are using NFSv2 with UDP?

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@...app.com
www.netapp.com

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