Date: Fri, 25 Jun 2010 02:38:59 +1000
From: Nick Piggin <npiggin@suse.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
       John Stultz <johnstul@us.ibm.com>, Frank Mayhar <fmayhar@google.com>,
       Eric Dumazet <dada1@cosmosbay.com>
Subject: Re: [patch 42/52] fs: icache per-cpu last_ino allocator
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On Thu, Jun 24, 2010 at 06:19:49PM +0200, Andi Kleen wrote:
> On Fri, Jun 25, 2010 at 01:52:43AM +1000, Nick Piggin wrote:
> > 
> > That's right. More or less it just requires alloc_inode to be exported,
> > adding more branches in new_inode would not be a good way to go.
> 
> One test/branch shouldn't hurt much. 

If we go through filesystems anyway may as well just use alloc_inode.

 
> > > I guess the main customer is sockets only.
> > 
> > I guess. Sockets and ram based filesystems. Interestingly I don't know
> > really what it's for (in socket code it's mostly for reporting and
> > hashing it seems). It sure isn't guaranteed to be unique.
> 
> Maybe it could be generated lazily on access for those?
> I suppose stat on a socket is relatively rare.
> The only problem is would need an accessor.
> 
> But ok out of scope.

Yea that might work. sock_i_ino() and ->dname covers a lot.


> > Well I think glibc will convert 64 bit stat struct to 32bit for
> > old apps. It detects if the ino can't fit in 32 bits.
> 
> ... and will fail the stat.

Which is what we're trying to avoid, I guess.

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