linux-kernel - Re: [patch 1/4] fs: cleanup files

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Message-ID: <20100604142052.GD26335@laptop>
Date:	Sat, 5 Jun 2010 00:20:52 +1000
From:	Nick Piggin <npiggin@...e.de>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Al Viro <viro@...IV.linux.org.uk>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Frank Mayhar <fmayhar@...gle.com>,
	John Stultz <johnstul@...ibm.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: Re: [patch 1/4] fs: cleanup files_lock

On Fri, Jun 04, 2010 at 04:38:18AM -0400, Christoph Hellwig wrote:
> On Fri, Jun 04, 2010 at 04:43:08PM +1000, Nick Piggin wrote:
> > Lock tty_files with a new spinlock, tty_files_lock; provide helpers to
> > manipulate the per-sb files list; unexport the files_lock spinlock.
> 
> I'm still not entirely happy with this.  You keep making the tty a
> special case by removing it from the files per-sb files list while
> nothing else in the system is removed from it.
> 
> Thinks would be much better if you could untangle the tty code from
> abuse of file->f_u.fu_list entirely.  And from a naive look at the
> tty code that actually seems pretty easy.  file->private for ttys
> currently directly points to the tty struct.  If you add a tty_private
> there which points back to the file, the tty and contains a list_head
> the open files in tty code tracking code can be completely divorced
> from the per-sb file tracking.

Well it is already a special case, I just switched it to using a
different lock for its private list. I wanted to keep surgery to
a minimum.


>  After that we can decide what to do
> with the per-sb file tracking, where my favourite still is to get
> rid of it entirely.

Again, this would be nice, but I didn't see an easy way to do it.
Even if refcounting obsoleted may_remount_ro, we still have
mark_files_ro. It's no more complex to rip this all out after my
patch. I don't see the problem in doing this patch. It has good
numbers.

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