linux-kernel - Re: [PATCH -tip] remove the BKL: Replace BKL in mount/umount syscalls with a mutex

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Date:	Thu, 16 Apr 2009 18:06:45 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Alessio Igor Bogani <abogani@...ware.it>,
	Alexander Viro <viro@....linux.org.uk>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH -tip] remove the BKL: Replace BKL in mount/umount
	syscalls with a mutex

* Alessio Igor Bogani <abogani@...ware.it> wrote:

> Replace ths BKL in sys_mount()/sys_umount() syscalls with a regular mutex.
> 
> Signed-off-by: Alessio Igor Bogani <abogani@...ware.it>
> ---
>  fs/namespace.c |   16 +++++++++-------
>  fs/super.c     |    9 ++++-----
>  2 files changed, 13 insertions(+), 12 deletions(-)

Ok, this patch needs to be flamed^W commented on by Al.

Al: this patch is very likely broken as i cannot imagine you leaving 
the BKL there just so. So lets accept that (and your NAK) as a given 
and not get upset about it too much.

We are willing to fix any side effects and preconditions before this 
can be done - and it would be nice if you could donate a few minutes 
to this effort by enumerating those preconditions for us, so that we 
can provide the real fixes. No-one knows this code better than you 
so even if we could guess our way around to a certain degree, some 
maintainer guidance and insight would be deeply appreciated.

I'm wondering how much the BKL use here is made necessary by the 
sys_open() BKL use in device drivers. Jonathan has done extensive 
work on the sys_open front (and there's more such work in 
tip:core/kill-the-BKL) - perhaps that has largely paved the way for 
this change?

There's also ioctl BKL use - is the BKL use here in sys_mount 
necessiated by the (naked) BKL use in those handlers?

Thanks,

	Ingo
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