linux-kernel - Re: [RESEND PATCH] fs/super.c set_anon

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Message-ID: <20121130040556.GD4939@ZenIV.linux.org.uk>
Date:	Fri, 30 Nov 2012 04:05:56 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Abhijit Pawar <abhi.c.pawar@...il.com>,
	linux-fsdevel@...r.kernel.org,
	"linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
	linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org
Subject: Re: [RESEND PATCH] fs/super.c set_anon_super calling optimization

On Fri, Oct 26, 2012 at 11:14:41AM -0200, Carlos Maiolino wrote:
> Hi,
> 
> On Thu, Oct 25, 2012 at 05:08:19PM +0530, Abhijit Pawar wrote:
> > Hi,
> > set_anon_super is called by many filesystems. Some call directly and
> > some call through the wrapper. Many of them in the wrapper's call to
> > this function are passing the second argument to this function which
> > is not used anywhere.
> > 
> > This patch replaces the second variable with NULL.
> > 
> 
> If the variable isn't used anymore, why don't just get rid of it, instead of
> call the function passing a NULL pointer on it?

	Because we want it to be a valid sget() callback.  I doubt that this
optimization is worth doing, though - might even micro-pessimize the things
on architectures where all arguments are passed in registers.
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