linux-kernel - Re: umount -l <path>, getcwd and /proc/<pid>/cwd inconsistent

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Message-Id: <1199698177.3156.79.camel@raven.themaw.net>
Date:	Mon, 07 Jan 2008 18:29:37 +0900
From:	Ian Kent <raven@...maw.net>
To:	bjdouma@...all.nl
Cc:	linux-kernel@...r.kernel.org
Subject: Re: umount -l <path>, getcwd and /proc/<pid>/cwd inconsistent


On Mon, 2008-01-07 at 17:55 +0900, Ian Kent wrote:
> On Mon, 2008-01-07 at 09:29 +0100, Bauke Jan Douma wrote:
> > Ian Kent wrote on 07-01-08 04:17:
> > > Hi all,
> > > 
> > > Could someone please help me understand what's happening with, what
> > > looks like inconsistent behavior, between getpwd and procfs readlink.
> > > 
> > > Basically, from a bash shell, setting working directory to a mounted
> > > directory all is fine with "pwd" and "/proc/<pid>/cwd". Following a
> > > "umount - l" on the mount "pwd" continues to return the expected string
> > > but "/proc/<pid>/cwd" returns an empty string.
> > > 
> > > What I'm really after is why this happens because sys_getcwd and
> > > proc_pid_readlink appear to do essentially the same thing to get the
> > > string.
> > > 
> > [snip]
> > 
> > What does `/bin/pwd' return, when you do that instead of
> > plain `pwd' (after the umount)?
> 
> I did check that at one point and it returned the same as pwd.
> I'll check again later, but I remember I explicitly checked that along
> the way.

Hey, I was sure I tested that.
It, in fact, returns nothing also.

Ian


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