From: Ingo Molnar <mingo@elte.hu>
To: Christoph Hellwig <hch@infradead.org>,
Alexander Viro <viro@ftp.linux.org.uk>
Cc: Alessio Igor Bogani <abogani@texware.it>,
Frederic Weisbecker <fweisbec@gmail.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
LKML <linux-kernel@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
viro@zeniv.linux.org.uk
Subject: Re: [PATCH -tip] remove the BKL: Replace BKL in mount/umount syscalls with a mutex
Date: Thu, 16 Apr 2009 18:49:27 +0200 [thread overview]
Message-ID: <20090416164927.GB19281@elte.hu> (raw)
In-Reply-To: <20090416143626.GA17683@infradead.org>
* Christoph Hellwig <hch@infradead.org> wrote:
> On Thu, Apr 16, 2009 at 04:27:58PM +0200, Alessio Igor Bogani wrote:
> > Replace ths BKL in sys_mount()/sys_umount() syscalls with a regular mutex.
>
> Could you try to explain what these actuall try to protect?
They dont really protect anything - the patch is wrong and
equivalent to a plain removal of the BKL.
The only case we found to ever matter in practice is NFS: it really
wants to get rid of the BKL in nfsd_get_sb(). So pushing down the
BKL lock into per filesystems and then removing it from NFS should
do the trick.
Would be nice to have some tentative Ack (or, a tentative
non-immediate-NAK) from Al before we go touch a lot of filesystems
though. Stupid dont-waste-human-effort considerations and stuff.
For us, the much simpler solution would be to drop the BKL in
nfsd_get_sb() and go on with life without to touch a dozen or so
filesystems. Alessio, mind trying that too, is it a solution for
your testcase?
Ingo
next prev parent reply other threads:[~2009-04-16 16:50 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-16 14:27 Alessio Igor Bogani
2009-04-16 14:36 ` Christoph Hellwig
2009-04-16 16:49 ` Ingo Molnar [this message]
2009-04-16 17:01 ` Christoph Hellwig
2009-04-16 17:13 ` Ingo Molnar
2009-04-17 0:05 ` Al Viro
2009-04-16 16:06 ` Ingo Molnar
2009-04-16 16:58 ` Ingo Molnar
2009-04-16 23:56 ` Al Viro
2009-04-17 0:01 ` Ingo Molnar
2009-04-17 0:13 ` Al Viro
2009-04-17 0:27 ` Ingo Molnar
2009-04-17 0:38 ` Al Viro
2009-04-17 16:56 ` Ingo Molnar
2009-04-17 17:04 ` Peter Zijlstra
2009-04-17 17:21 ` Linus Torvalds
2009-04-17 17:31 ` Jonathan Corbet
2009-04-17 18:03 ` Linus Torvalds
2009-04-17 18:44 ` Matthew Wilcox
2009-04-22 17:28 ` J. Bruce Fields
2009-04-17 18:08 ` Al Viro
2009-04-17 18:34 ` Ingo Molnar
2009-04-17 17:41 ` Al Viro
2009-04-17 17:34 ` Al Viro
2009-04-16 23:49 ` Al Viro
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