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Date: Fri, 8 Jun 2012 23:27:34 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
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Subject: Re: [RFC, PATCH, RESEND] fs: push rcu_barrier() from
 deactivate_locked_super() to filesystems
Message-ID: <20120608222734.GT30000@ZenIV.linux.org.uk>
References: <1339191663-17693-1-git-send-email-kirill.shutemov@linux.intel.com>
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 <20120608221446.GA18250@otc-wbsnb-06>
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On Fri, Jun 08, 2012 at 03:25:50PM -0700, Andrew Morton wrote:

> A neater implementation might be to add a kmem_cache* argument to
> unregister_filesystem().  If that is non-NULL, unregister_filesystem()
> does the rcu_barrier() and destroys the cache.  That way we get to
> delete (rather than add) a bunch of code from all filesystems and new
> and out-of-tree filesystems cannot forget to perform the rcu_barrier().

There's often enough more than one cache, so that one is no-go.