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To:     NeilBrown <neilb@suse.com>
Cc:     "bcodding\@redhat.com" <bcodding@redhat.com>,
        "linux-nfs\@vger.kernel.org" <linux-nfs@vger.kernel.org>,
        linux-nfs-owner@vger.kernel.org,
        "malahal\@gmail.com" <malahal@gmail.com>,
        "mbenjami\@redhat.com" <mbenjami@redhat.com>,
        Trond Myklebust <trondmy@hammerspace.com>
Subject: Re: "(deleted)" directories
From:   "Marc Eshel" <eshel@us.ibm.com>
Date:   Sun, 4 Nov 2018 11:47:24 -0800
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linux-nfs-owner@vger.kernel.org wrote on 11/03/2018 10:31:29 PM:

> From: NeilBrown <neilb@suse.com>
> To: Marc Eshel <eshel@us.ibm.com>, Trond Myklebust 
<trondmy@hammerspace.com>
> Cc: "bcodding\@redhat.com" <bcodding@redhat.com>, "linux-nfs
> \@vger.kernel.org" <linux-nfs@vger.kernel.org>, linux-nfs-
> owner@vger.kernel.org, "malahal\@gmail.com" <malahal@gmail.com>, 
> "mbenjami\@redhat.com" <mbenjami@redhat.com>
> Date: 11/03/2018 10:41 PM
> Subject: Re: "(deleted)" directories
> Sent by: linux-nfs-owner@vger.kernel.org
> 
> On Fri, Nov 02 2018, Marc Eshel wrote:
> 
> > One reason to have different FHs for the same file is that a file can 
be 
> > linked from multiple directories.
> 
> This has some based when considering filehandles for non-directories.
> However the original problem was with filehandles for directories.....

This was just an example of why FH might be different, I don't think we 
depend on it for the parent information anymore. Malahal listed some other 
reasons for having different FH for the same file. I believe that Ganesha 
split the FH to the key portion (the unique id of the file) and some other 
information that is file system dependent. If the NFS client can not 
handle the spec definition of FH maybe the spec should be updated to 
something like Ganesha does.
Marc. 

> 
> > Adding the parent inode to the FH help finding the the name of the 
file by 
> > looking for the file inode in
> > the parent directoy.
> >
> 
> ....and directories have a ".." link, obviating the need to store parent
> information in the filehandle.
> 
> NeilBrown
> 
> 
> > Marc.
> >
> > linux-nfs-owner@vger.kernel.org wrote on 11/02/2018 05:15:42 PM:
> >
> >> From: Trond Myklebust <trondmy@hammerspace.com>
> >> To: "mbenjami@redhat.com" <mbenjami@redhat.com>
> >> Cc: "bcodding@redhat.com" <bcodding@redhat.com>, "malahal@gmail.com"
> >> <malahal@gmail.com>, "linux-nfs@vger.kernel.org" 
> > <linux-nfs@vger.kernel.org>
> >> Date: 11/02/2018 05:15 PM
> >> Subject: Re: "(deleted)" directories
> >> Sent by: linux-nfs-owner@vger.kernel.org
> >> 
> >> On Fri, 2018-11-02 at 18:07 -0400, Matt Benjamin wrote:
> >> > It sounds like a pretty good one, that goes to the heart of what a
> >> > specification is
> >> > 
> >> 
> >> While admittedly it is (still) Dia de los Muertos today, I would 
think
> >> that someone who resurrected a part of the NFSv3 spec that has been
> >> unused for the full 23 years of its existence might have some
> >> explanation for why they did so?
> >> 
> >> IOW: not being of a particularly religious persuasion, I usually want
> >> to understand why features are needed rather than having blind faith 
in
> >> the person who wrote the spec.
> >> 
> >> > Matt
> >> > 
> >> > On Fri, Nov 2, 2018 at 4:26 PM, Trond Myklebust <
> >> > trondmy@hammerspace.com> wrote:
> >> > > On Fri, 2018-11-02 at 21:24 +0530, Malahal Naineni wrote:
> >> > > > Ben, NFSv3 RFC1813.txt states: "If two file handles from the 
same
> >> > > > server are equal, they must refer to the same file, but if
> >> > > > they  are
> >> > > > not equal, no conclusions can be drawn." Ganesha does return 
same
> >> > > > fileid here (inode).
> >> > > > 
> >> > > > In NFSv4, they have introduced "unique_handles" attribute. I
> >> > > > don't
> >> > > > see
> >> > > > Linux NFS client using this at all though.
> >> > > 
> >> > > Why does your server need to have multiple filehandles refer to 
the
> >> > > same file, and why do you expect clients to support this?
> >> > > 
> >> > > Yes, the spec allows it, but that's not a sufficient reason.
> >> > > 
> >> > > > Regards, Malahal.
> >> > > > On Fri, Nov 2, 2018 at 4:35 PM Benjamin Coddington <
> >> > > > bcodding@redhat.com> wrote:
> >> > > > > On 2 Nov 2018, at 1:26, Malahal Naineni wrote:
> >> > > > > 
> >> > > > > > Hi All, we are using NFS-Ganesha with Linux NFS clients. 
The
> >> > > > > > client's
> >> > > > > > shell reports the following. Based on lsof, the directory 
is
> >> > > > > > marked
> >> > > > > > deleted. "cd to ROOT and cd to the same home directory 
fixes
> >> > > > > > the
> >> > > > > > issue. The client behaves as though the directory is 
deleted
> >> > > > > > and
> >> > > > > > recreated! Our NFS-Ganesha server implementation uses
> >> > > > > > multiple
> >> > > > > > file
> >> > > > > > handles that point to the same object. NFS spec says this
> >> > > > > > should
> >> > > > > > be
> >> > > > > > fine, but Linux NFS seems to be broken in this regard.
> >> > > > > > tcpdump
> >> > > > > > does
> >> > > > > > indicate file handle change (note that all file handles are
> >> > > > > > permanent,
> >> > > > > > meaning they are valid at the server any time) around this
> >> > > > > > issue
> >> > > > > > time.
> >> > > > > > 
> >> > > > > > "shell-init: error retrieving current directory: getcwd:
> >> > > > > > cannot
> >> > > > > > access
> >> > > > > > parent directories: No such file or directory"
> >> > > > > > sh        112544            malahal  cwd       DIR
> >> > > > > > 0,67
> >> > > > > >      65536   45605209 /home/malahal (deleted)
> >> > > > > > (10.120.154.42:/nfs/malahal-export/)
> >> > > > > > 
> >> > > > > > Function nfs_prime_dcache() seems to invalidate the dcache
> >> > > > > > entry
> >> > > > > > if
> >> > > > > > nfs_same_file() returns false. nfs_same_file() does seem to
> >> > > > > > return
> >> > > > > > false with the following change, if I read it correctly, if
> >> > > > > > there
> >> > > > > > is a
> >> > > > > > file handle change. Can this be the source of my issue? It
> >> > > > > > seems
> >> > > > > > that
> >> > > > > > the client should do this only if the file handle is NOT
> >> > > > > > valid
> >> > > > > > (e.g.
> >> > > > > > if it gets ESTALE), right?
> >> > > > > > 
> >> > > > > > The following commit seems to assume that the objects are
> >> > > > > > different if
> >> > > > > > they have different file handles!
> >> > > > > > commit 7dc72d5f7a0ec97a53e126c46e2cbd2560757955
> >> > > > > > Author: Trond Myklebust <trond.myklebust@primarydata.com>
> >> > > > > > Date:   Thu Sep 22 13:38:52 2016 -0400
> >> > > > > > 
> >> > > > > >     NFS: Fix inode corruption in nfs_prime_dcache()
> >> > > > > 
> >> > > > > My understanding is that for NFSv3 we have to assume that
> >> > > > > distinct
> >> > > > > filehandles are distinct objects, but maybe I'm wrong about
> >> > > > > this.
> >> > > > > 
> >> > > > > For NFSv4.x, we can follow the guidance in RFCs 5661 or 7530
> >> > > > > section 10.3.4
> >> > > > > to determine if the differing filehandles are the same 
object,
> >> > > > > specifically
> >> > > > > the fileid recommended attribute needs to be implemented.  Is
> >> > > > > Ganesha
> >> > > > > returning the same fileid for both filehandles?
> >> > > > > 
> >> > > > > Ben
> >> > > --
> >> > > Trond Myklebust
> >> > > CTO, Hammerspace Inc
> >> > > 4300 El Camino Real, Suite 105
> >> > > Los Altos, CA 94022
> >> > > www.hammer.space
> >> > > 
> >> > > 
> >> > 
> >> > 
> >> -- 
> >> Trond Myklebust
> >> CTO, Hammerspace Inc
> >> 4300 El Camino Real, Suite 105
> >> Los Altos, CA 94022
> >> www.hammer.space
> >> 
> >> 
> [attachment "signature.asc" deleted by Marc Eshel/Almaden/IBM]