linux-kernel - Re: [RFC] fs/super.c: Why alloc_super use a static variable default

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Date:	Wed, 25 Jul 2007 12:29:17 +0800
From:	"rae l" <crquan@...il.com>
To:	"Al Viro" <viro@....linux.org.uk>
Cc:	"Alexander Viro" <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org, "Greg Kroah-Hartman" <gregkh@...e.de>
Subject: Re: [RFC] fs/super.c: Why alloc_super use a static variable default_op?

On 7/25/07, Al Viro <viro@....linux.org.uk> wrote:
> On Wed, Jul 25, 2007 at 11:48:35AM +0800, rae l wrote:
> > Why alloc_super use a static variable default_op?
> > the static struct super_operations default_op is just all zeros, and
> > just referenced as the initial value of a new allocated super_block,
> > what does it for?
>
> So that we would not have to care about ->s_op *ever* being NULL.
But is it valuable? Compared to a waste of sizeof(struct super_block)
bytes memory.

When some code want to refer fs_type->s_op, it almost always want to
refer some function pointer in s_op with fs_type->s_op->***, but all
pointers in default_op are all NULLs, what about this scenario?

and if you do grep s_op in the source code, you will found nowhere
will want to test s_op or dependent on s_op not NULL.

So my opinion is to remove default_ops, just keep new allocated s_op NULL.

>


-- 
Denis Cheng
Linux Application Developer

"One of my most productive days was throwing away 1000 lines of code."
 - Ken Thompson.
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