Re: [patch 1/4] fs: cleanup files_lock

[Nick Piggin <npiggin@suse.de>]

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.