linux-kernel - Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry

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Message-id: <454858F2.5020206@cosmosbay.com>
Date:	Wed, 01 Nov 2006 09:21:06 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC, PATCH] dont insert sockets/pipes dentries into
 dentry_hashtable.

David Miller a écrit :
> From: Eric Dumazet <dada1@...mosbay.com>
> Date: Tue, 31 Oct 2006 19:48:48 +0100
> 
>> We currently insert sockets/pipes dentries into the global dentry
>> hashtable.  This is *useless* because there is currently no way
>> these entries can be used for a lookup(). (/proc/xxx/fd/xxx uses a
>> different mechanism)
> 
> It turns out that while procfs uses a different "mechanism", those
> procfs symlinks do point to the real socket dentry, so when you
> readlink() on it you do d_path() on the real socket dentry.
> 
> If you unhash these things, I'm pretty sure you'll see an ugly
> "(deleted)" at the end of the symlink string for /proc/$pid/fd/$X
> files that are sockets or something like that.

No no, my patch takes care of that.

You still see the right link for pipes and sockets on /proc/$pid/fd/XXX

And " (deleted)" is correctly added to deleted files.


> 
> Al Viro just suggested a way around this to me:
> 
> 1) Just mark the dentry HASHED by hand in the dentry flags, but don't
>    actually hash it.
> 
> 2) Create a special dentry->d_deleted method for sockets that returns
>    0 and clears by hand the HASHED flag bit in the dentry (see what
>    dput() does when this happens).
> 
> It's an abuse but it will work.
> 
Why hack when a proper thing can be done ?

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