amd64/161493: NFS v3 directory structure update slow

Thu Oct 13 02:25:47 UTC 2011

George Breahna wrote:
> I just about to write back to mention this.
> 
> I "fixed" the problem by running with -o but the old server still has
> that problem but very rarely. The new server is affected 100% of the
> time for some reason.
> 
Well, the problem was that the new field in struct nameidata wasn't
initialized by the NFS servers. As such, it just depends on what
happens to be on the stack, complicated slightly by cases where the
test of the variable is != 0 vs another case where it must be 1 for
the problem to show up.

> If I'm not using NFSv4 is there a performance reason why I should
> still use the new nfs server over the old one ?
> 
The new/default server uses a different duplicate request cache
specifically designed for NFS, including over TCP. I hope that this
cache will work more efficiently than the generic (knows nothing
about NFS) one in the krpc, which is what the old server uses.

Whether this has any real effect on performance for your case,
I can't say.

Try the patches. I think both will work ok after the patches are
applied, since they specifically fixed a problem w.r.t. lookup of "..".

rick
> Thank you very much for your help guys.
> 
> George
> 
> -----Original Message-----
> From: Rick Macklem [mailto:rmacklem at uoguelph.ca]
> Sent: Wednesday, October 12, 2011 10:17 PM
> To: George Breahna
> Cc: freebsd-amd64 at freebsd.org; John Baldwin
> Subject: Re: amd64/161493: NFS v3 directory structure update slow
> 
> George Breahna wrote:
> > Ok, I will try this.
> >
> > I noticed you wrote another patch, available here, called the dotdot
> > patch. It modifies another file on top of the one mentioned in the
> > link you gave me. Is that unnecessary now ?
> >
> > http://people.freebsd.org/~rmacklem/dotdot.patch
> >
> The above patch also fixed the old server. See below for the patch
> for the old server. (You will be running the old server if you start
> both mountd and nfsd with a "-o" option. This happens if you have
> oldnfs_server_enable="YES"
> in your /etc/rc.conf.)
> 
> Since "nfsstat -s" shows non-zero counts, you are running the
> new/default server. ("nfsstat -o -s" reports stats for the old
> server, which should be all zeros if you are running the new/default
> one.)
> 
> In summary, I don't think you are running the old server and only
> need to patch the old server if you choose to run it, as jhb@
> suggested
> to help with isolating the problem. (I would suggest you do that, if
> the patch for the new/regular server doesn't fix the problem.)
> 
> > George
> >
> > -----Original Message-----
> > From: Rick Macklem [mailto:rmacklem at uoguelph.ca]
> > Sent: Wednesday, October 12, 2011 8:25 PM
> > To: John Baldwin
> > Cc: George Breahna; freebsd-gnats-submit at freebsd.org; Rick Macklem;
> > freebsd-amd64 at freebsd.org
> > Subject: Re: amd64/161493: NFS v3 directory structure update slow
> >
> > John Baldwin wrote:
> > > On Tuesday, October 11, 2011 11:07:13 am George Breahna wrote:
> > > >
> > > > >Number: 161493
> > > > >Category: amd64
> > > > >Synopsis: NFS v3 directory structure update slow
> > > > >Confidential: no
> > > > >Severity: critical
> > > > >Priority: high
> > > > >Responsible: freebsd-amd64
> > > > >State: open
> > > > >Quarter:
> > > > >Keywords:
> > > > >Date-Required:
> > > > >Class: sw-bug
> > > > >Submitter-Id: current-users
> > > > >Arrival-Date: Tue Oct 11 15:10:07 UTC 2011
> > > > >Closed-Date:
> > > > >Last-Modified:
> > > > >Originator: George Breahna
> > > > >Release: 9.0 Beta 2
> > > > >Organization:
> > > > >Environment:
> > > > FreeBSD store2 9.0-BETA2 FreeBSD 9.0-BETA2 #0: Sun Sep 18
> > > > 22:02:45
> > > > EDT 2011
> > > pulsar at store2.emailarray.com:/usr/obj/usr/src/sys/PULSAR amd64
> > > > >Description:
> > > > We used to run a NFS server on FreeBSD 6.2 but we built a new
> > > > box
> > > > recently
> > > and installed 9.0 Beta 2 on it. The data was moved over as it
> > > serves
> > > as the
> > > back-end for a mail system. It runs NFS v3 over TCP only and all
> > > the
> > > NFS-
> > > related processes (rpcbind, mountd, lockd, etc ) run with the -h
> > > switch and
> > > bind to the local IP address.
> > > >
> > > > The NFS server exports the data to 7 NFS clients ranging from
> > > > FreeBSD 6.1 to
> > > 8.2, the majority being 8.2 The mount on the NFS clients is done
> > > simply with -
> > > o tcp,rsize=32768,wsize=32768
> > > >
> > > > Usual file operations, such as accessing files, creating
> > > > directories,
> > > removing files, chmod, chown, etc work perfectly but we noticed
> > > there
> > > were
> > > issues in removing directories that contained data. We had a
> > > strange
> > > error:
> > > >
> > > > rm -rf nick/
> > > > rm: fts_read: Input/output error
> > > >
> > > > Using 'truss' on rm revealed this:
> > > >
> > > > open("..",O_RDONLY,00) ERR#5 'Input/output error'
> > > >
> > > > After much testing and debugging we realized the problem is in
> > > > the
> > > > NFS
> > > protocol. ( either server or client but we assume server since
> > > this
> > > used to
> > > work very well with FreeBSD 6.2 ). The problem appears to be that
> > > NFS
> > > does not
> > > show the '..' after modifying a directory structure. Take the
> > > following
> > > example executed on a FreeBSD 8.2 client accessing the NFS share
> > > from
> > > the
> > > 9.0B2 server:
> > > >
> > > > imap5# mkdir test1
> > > > imap5# cd test1
> > > > imap5# touch file1
> > > > imap5# touch file2
> > > > imap5# ls -la
> > > > ls: ..: Input/output error
> > > > total 4
> > > > drwxr-xr-x 2 root vchkpw 512 Oct 11 10:55 .
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:55 file1
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:55 file2
> > > >
> > > > Notice the '..' is missing from the display. If we now try and
> > > > remove the
> > > directory 'test1' it will throw the "rm: fts_read: Input/output
> > > error"
> > > error.
> > > >
> > > > If we wait in between 1 minute and 5 minutes, '..' will
> > > > eventually
> > > > appear by
> > > itself. During this whole time, '..' effectively exists on the NFS
> > > server but
> > > it's not displayed by any of the NFS clients.
> > > >
> > > > I can force the NFS client to show it faster by doing an ls -la
> > > > from
> > > > the
> > > parent level. For example:
> > > >
> > > > imap5# mkdir test1
> > > > imap5# touch test1/file1
> > > > imap5# touch test1/file2
> > > > imap5# touch test1/file3
> > > > imap5# ls -la test1
> > > > total 8
> > > > drwxr-xr-x 2 root vchkpw 512 Oct 11 10:59 .
> > > > drwx------ 10 vpopmail vchkpw 1024 Oct 11 10:59 ..
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file1
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file2
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file3
> > > > imap5# cd test1
> > > > imap5# ls -la
> > > > total 8
> > > > drwxr-xr-x 2 root vchkpw 512 Oct 11 10:59 .
> > > > drwx------ 10 vpopmail vchkpw 1024 Oct 11 10:59 ..
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file1
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file2
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file3
> > > >
> > > > but if we wait 5 seconds after that display and try again:
> > > >
> > > > ls -la
> > > > ls: ..: Input/output error
> > > > total 4
> > > > drwxr-xr-x 2 root vchkpw 512 Oct 11 10:59 .
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file1
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file2
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:59 file3
> > > >
> > > > Again, if we wait longer ( 1-5 minutes ), the '..' will properly
> > > > appear in
> > > there.
> > > >
> > > > There are no error messages on the console or other log files.
> > > > This
> > > > is
> > > reproducible 100% of the time with any FreeBSD client. Have tried
> > > unmounting/remounting several times without any effect. Also tried
> > > different
> > > rsize/wsize, no effect. I think there is some delay in updating
> > > the
> > > directory
> > > structure and it's causing this bug.
> > > >
> > > > Here's also some output from nfsstat on the server:
> > > >
> > > >
> > > > Server Info:
> > > >   Getattr Setattr Lookup Readlink Read Write Create
> > > Remove
> > > > 114731225 20496896 254966151 133 11697392 19963641 0
> > > 9228861
> > > >    Rename Link Symlink Mkdir Rmdir Readdir RdirPlus
> > > Access
> > > >   4313471 1157651 39 1955 16511932 15479669 0
> > > 116927742
> > > >     Mknod Fsstat Fsinfo PathConf Commit
> > > >         0 4748487 48 0 14921747
> > > > Server Ret-Failed
> > > >                 0
> > > > Server Faults
> > > >             0
> > > > Server Cache Stats:
> > > >    Inprog Idem Non-idem Misses
> > > >         0 0 0 613368147
> > > > Server Write Gathering:
> > > >  WriteOps WriteRPC Opsaved
> > > >  19963641 19963641 0
> > > >
> > > > >How-To-Repeat:
> > > > imap5# mkdir test1
> > > > imap5# cd test1
> > > > imap5# touch file1
> > > > imap5# touch file2
> > > > imap5# ls -la
> > > > ls: ..: Input/output error
> > > > total 4
> > > > drwxr-xr-x 2 root vchkpw 512 Oct 11 10:55 .
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:55 file1
> > > > -rw-r--r-- 1 root vchkpw 0 Oct 11 10:55 file2
> > > > >Fix:
> > >
> > > Can you try using the "old" NFS server as a test?
> > >
> > Please make sure you have the patch in r225356 in your server's
> > kernel sources (it went into head on Sep. 3, but I don't know if
> > your Sep. 11 build would have it?). It fixed a problem that would
> > cause lookup of ".." to fail intermittently, because a field in
> > struct nameidata added on Aug. 13 wasn't initialized.
> >
> > You can find the one line patch here:
> > http://svnweb.freebsd.org/base/head/sys/fs/nfsserver/nfs_nfsdport.c?r1=224911&r2=225356
> 
> Clarification, this is the patch for the new/default server. There is
> a
> similar patch for the old server. For the old server, the patch is:
> http://svnweb.freebsd.org/base/head/sys/nfsserver/nfs_serv.c?r1=219028&r2=225356
> 
> rick
> >
> > Please let us know if you have this patch and, if not, apply it
> > and see if the problem goes away.
> >
> > Thanks, rick