linux-kernel - Re: [patch 01/28] fs: d

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Message-ID: <20101119050108.GB3284@amd>
Date:	Fri, 19 Nov 2010 16:01:08 +1100
From:	Nick Piggin <npiggin@...nel.dk>
To:	David Miller <davem@...emloft.net>
Cc:	npiggin@...nel.dk, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 01/28] fs: d_validate fixes

On Thu, Nov 18, 2010 at 12:51:23PM -0800, David Miller wrote:
> From: Nick Piggin <npiggin@...nel.dk>
> Date: Wed, 17 Nov 2010 01:09:01 +1100
> 
> > d_validate has been broken for a long time.
> > 
> > kmem_ptr_validate does not guarantee that a pointer can be dereferenced
> > if it can go away at any time. Even rcu_read_lock doesn't help, because
> > the pointer might be queued in RCU callbacks but not executed yet.
> > 
> > So the parent cannot be checked, nor the name hashed. The dentry pointer
> > can not be touched until it can be verified under lock. Hashing simply
> > cannot be used.
> > 
> > Instead, verify the parent/child relationship by traversing parent's
> > d_child list. It's slow, but only ncpfs and the destaged smbfs care
> > about it, at this point.
> > 
> > Signed-off-by: Nick Piggin <npiggin@...nel.dk>
> 
> This won't apply because is conflicts with Christoph Hellwig's
> RCU conversion of d_validate().
> 
> Which is a change that went in more than a month ago.

Sorry yeah I had a local revert that I didn't send out, otherwise
it should be a vanilla upstream kernel.

 
> Thus I'd really appreciate if you mentioned what tree your patches are
> against in your "0/N" posting, always.

Try to remember. I'll put some time into polishing up a git tree
and submitting the more interesting patches as well, this weekend.

Thanks,
Nick
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