linux-kernel - Re: [Patch] debugfs: remove module

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Date:	Wed, 1 Dec 2010 07:56:35 -0800
From:	Greg KH <gregkh@...e.de>
To:	Cong Wang <amwang@...hat.com>
Cc:	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [Patch] debugfs: remove module_exit()

On Wed, Dec 01, 2010 at 02:33:12PM +0800, Cong Wang wrote:
> On 12/01/10 09:35, Greg KH wrote:
> >On Tue, Nov 09, 2010 at 04:19:58AM -0500, Amerigo Wang wrote:
> >>debugfs can't be a module, so module_exit() is meaningless
> >>for it.
> >>
> >>Signed-off-by: WANG Cong<amwang@...hat.com>
> >>
> >>---
> >>diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
> >>index 37a8ca7..d38c88f 100644
> >>--- a/fs/debugfs/inode.c
> >>+++ b/fs/debugfs/inode.c
> >>@@ -13,9 +13,6 @@
> >>   *
> >>   */
> >>
> >>-/* uncomment to get debug messages from the debug filesystem, ah the irony. */
> >>-/* #define DEBUG */
> >
> >Why did you remove these lines?  They don't pertain to this patch.
> 
> These lines are obsolete.

Even if they were (and hint, I don't think they are), they have nothing
to do with the patch you created so they don't belong here.  The rule is
"one patch per logical change" and you didn't even describe that you
were removing these lines in the changelog entry, so that's two strikes
against removing these lines.

> >>-
> >>  #include<linux/module.h>
> >>  #include<linux/fs.h>
> >>  #include<linux/mount.h>
> >>@@ -540,17 +537,5 @@ static int __init debugfs_init(void)
> >>
> >>  	return retval;
> >>  }
> >>-
> >>-static void __exit debugfs_exit(void)
> >>-{
> >>-	debugfs_registered = false;
> >>-
> >>-	simple_release_fs(&debugfs_mount,&debugfs_mount_count);
> >>-	unregister_filesystem(&debug_fs_type);
> >>-	kobject_put(debug_kobj);
> >>-}
> >
> >When the code is built into the kernel, the __exit function should go
> >away, so this isn't costing us any extra memory, right?
> 
> 
> Perhaps, but this can still reduce the vmlinux size, right?

Which really doesn't matter, right?  How much is it reduced?

> >And debugfs used to be able to be built as a module, perhaps it will be
> >in the future?  I don't think this patch is really needed.
> >
> 
> Huh? Wasn't it a module before?

Yes it was.

> I think the problem is tracers use debugfs, it needs to depends on DEBUGFS=y.

So if you disable tracing, then you could use debugfs as a module,
right?  So the patch should not be applied.

thanks,

greg k-h
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