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From:   Ashish Sangwan <ashishsangwan2@gmail.com>
Date:   Fri, 14 Dec 2018 10:41:05 +0530
Message-ID: <CAOiN93kfW2H_OEfUGxC4UKJPvn8Lo5Bpkf77UKcxHwWsBwEhXg@mail.gmail.com>
Subject: Re: Handling of duplicate inode numbers for the directories in the
 nfs v3 kernel client
To:     ffilz@redhat.com
Cc:     linux-nfs@vger.kernel.org, neilb@suse.com
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On Thu, Dec 13, 2018 at 9:56 PM Frank Filz <ffilz@redhat.com> wrote:
>
> On 12/12/18 10:57 AM, Ashish Sangwan wrote:
> > Hi,
> >
> > Our NFS filer can sometimes return same inode number for different directories.
> > For example /mnt/dir1/dir2 and /mnt/dir3/dir4, in same rare cases dir2
> > and dir4 might end up returning the same inode number to the client.
> > Though it can never happen that inode numbers will be same for two
> > directories and also there parent is same. Can linux client handle
> > this case? What issues it can cause?
> > https://lkml.org/lkml/2006/10/2/346
> > I stumbled upon this thread where it is written that nfs client can
> > handle this but userspace will see inode collisions. Given that this
> > will happen only for directories, userspace utils logic might not get
> > affected from this as hardlinks on directories are not possible. But
> > the thread is really old. Wanted to confirm if this holds true even
> > now.
> >
> > Thanks,
> > Ashish
>
> The find tool will detect the collisions and report them, and if I
> recall it stops proceeding down the directory tree from the duplicate
> inode number. I know for sure I've seen it complain, and pretty sure I
> saw it stop descending the tree into the directory with the duplicate
> inode number.
>

True. Was just looking into the find code to check how they detect cycles.
They are using pair of "device node : inode number" so find will
certainly complain.

>
> Frank
>