From: Nick Piggin <npiggin@kernel.dk>
To: Christoph Hellwig <hch@lst.de>
Cc: Nick Piggin <npiggin@kernel.dk>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@ZenIV.linux.org.uk>,
linux-fsdevel@vger.kernel.org
Subject: Re: Patch "fs: use RCU read side protection in d_validate" broken
Date: Tue, 16 Nov 2010 09:51:08 +1100 [thread overview]
Message-ID: <20101115225108.GA3540@amd> (raw)
In-Reply-To: <20101115210906.GA5964@lst.de>
On Mon, Nov 15, 2010 at 10:09:06PM +0100, Christoph Hellwig wrote:
> On Mon, Nov 15, 2010 at 04:11:20PM +1100, Nick Piggin wrote:
> > This patch is totally broken. You can't just dget() a dentry with
> > nothing but RCU critical section open.
>
> The plain dget is indeed wrong as we should at least take d_lock
> and check d_count for zero before incrementing it to protect
> against shrink_dentry_list.
>
> I'm not quite sure it really matters as d_validate already has
Explain why it doesn't matter. It's an oopsable bug introduced.
> and always ad much worse bugs, such as the complete lack of
> protection against renames.
What are the much worse bugs? What do you mean by rename protection?
> Anyway, I'll send a patch to Linus to fix this issue for now.
A revert is appropriate. Like I said, there is no need for this patch at
all and no justification provided.
prev parent reply other threads:[~2010-11-15 22:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-15 5:11 Patch "fs: use RCU read side protection in d_validate" broken Nick Piggin
2010-11-15 5:32 ` Nick Piggin
2010-11-15 21:16 ` Christoph Hellwig
2010-11-15 23:06 ` Nick Piggin
2010-11-15 21:09 ` Christoph Hellwig
2010-11-15 22:51 ` Nick Piggin [this message]
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