linux-kernel - Re: [PATCH -stable] sysfs: disable reclamation by default

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Message-ID: <20070517120423.GE17712@kroah.com>
Date:	Thu, 17 May 2007 05:04:23 -0700
From:	Greg KH <greg@...ah.com>
To:	Tejun Heo <htejun@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Clemens Schwaighofer <cs@...uila.co.jp>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Maneesh Soni <maneesh@...ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Chuck Ebbert <cebbert@...hat.com>
Subject: Re: [PATCH -stable] sysfs: disable reclamation by default

On Wed, May 16, 2007 at 08:31:00PM +0200, Tejun Heo wrote:
> sd->s_dentry updates made by dentry/inode reclamation are racy and can
> lead to BUG() or oops.  This is already fixed in -mm and the fix is
> scheduled to be merged into upstream for 2.6.23 but the fix
> reimplements sysfs dentry dropping and is too risky for -stable
> kernels.
> 
> This is an interim solution for -stable kernels.  sysfs reclamation is
> disabled by default and can be enabled by using sysfs.enable_reclaim
> kernel parameter.  Note that dentries are still created on demand, so
> attribute and symlinks nodes aren't allocated on creation.  They're
> allocated on first lookup and deallocated when the sysfs node is
> removed.

Ick, this is going to kill memory on big boxes (s390 and others) and I
don't really want to apply this it if at all possible.

Maneesh, any other thoughts?

thanks,

greg k-h
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