linux-kernel - Re: [PATCH] proc: stop using BKL

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Message-ID: <20081024155515.GA12984@infradead.org>
Date:	Fri, 24 Oct 2008 11:55:15 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk
Subject: Re: [PATCH] proc: stop using BKL

On Fri, Oct 24, 2008 at 03:46:06PM +0400, Alexey Dobriyan wrote:
>     3) proc_readdir_de()
>     --------------------
>     "." and ".." part doesn't need BKL, walking PDE list is under
>     proc_subdir_lock, calling filldir callback is potentially blocking
>     because it writes to luserspace. All proc_readdir_de() callers
>     eventually come from ->readdir hook which is under directory's
>     ->i_mutex -- BKL doesn't protect anything.
>     
>     4) proc_root_readdir_de()
>     -------------------------
>     proc_root_readdir_de is ->readdir hook, see (3).
>     
>     Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>

Once you stop taking BKL in readdir you also need to switch to
generic_file_llseek for those directories.  It would be good if you
could switch the fallback proc_reg_llseek to no llseek at all in
proc_reg_llseek while you're at it.  I'll prepare a similar change
for non-procfs fops instances.

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