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

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Message-Id: <20101118.125123.241932424.davem@davemloft.net>
Date:	Thu, 18 Nov 2010 12:51:23 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	npiggin@...nel.dk
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 01/28] fs: d_validate fixes

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.

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

Thanks.
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