linux-kernel - Re: [PULL REQUEST] ext3, jbd, ext2, and quota fixes for 3.1-rc1

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Message-ID: <20110726185920.GA2970@infradead.org>
Date:	Tue, 26 Jul 2011 14:59:20 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jan Kara <jack@...e.cz>, Josef Bacik <josef@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PULL REQUEST] ext3, jbd, ext2, and quota fixes for 3.1-rc1

On Tue, Jul 26, 2011 at 07:52:20PM +0100, Al Viro wrote:
> Note that dentry obviously can't be NULL there.  dentry->d_parent is never
> NULL.  And dentry->d_parent would better not be negative, for crying out
> loud!  What's worse, there's no guarantees that dentry->d_parent will
> remain our parent over that sync_mapping_buffers() *and* that inode won't
> just be freed under us (after rename() and memory pressure leading to
> eviction of what used to be our dentry->d_parent).  Moreover, even if
> inode survives in icache, there is no promise that it will have an alias
> in dcache by the time we get to the next iteration of the loop, so this
> list_entry() next time around can bloody well happen to &inode->i_dentry,
> dentry being a garbage address somewhere inside that struct inode (or a
> bit above it - I hadn't compared offsets).

In addition to beeing bogus the code also is useless.  fsync on a file
explicitly does not guarantee anything at all about the parent, and
never really has on Linux either.

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