linux-ext4 - Re: [PATCH] ext4: take i_mutex in ext4_symlink to eliminate a warning from ext4

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Message-ID: <20130327134110.GI5861@thunk.org>
Date:	Wed, 27 Mar 2013 09:41:10 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Zheng Liu <gnehzuil.liu@...il.com>
Cc:	linux-ext4@...r.kernel.org, Zheng Liu <wenqing.lz@...bao.com>
Subject: Re: [PATCH] ext4: take i_mutex in ext4_symlink to eliminate a
 warning from ext4_truncate

On Wed, Mar 27, 2013 at 09:19:07PM +0800, Zheng Liu wrote:
> From: Zheng Liu <wenqing.lz@...bao.com>
> 
> After applied this commit (8e4061cb), we will get a warning from
> ext4_truncate when i_mutex isn't taken.  Here the assumption is that
> i_mutex should be taken when we do a truncation.  In ext4_symlink we
> could need to call ext4_truncate to trim some blocks beyond i_size, but
> the i_mutex isn't taken.

Hmm, and this is why I added the warning.  Even after looking your
patch, I'm having trouble finding the codepath that results in
ext4_truncate() getting called from __page_symlink().  Can you send
the stack trace from the WARN_ON, just so I can see what I missed?

Thanks,

						- Ted
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