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Re: [RFC] Badness in __mutex_unlock_slowpath with XFS stress tests

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>, Nathan Scott <nathans@xxxxxxx>, Suzuki <suzuki@xxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, "linux-aio kvack.org" <linux-aio@xxxxxxxxx>, lkml <linux-kernel@xxxxxxxxxxxxxxx>, akpm@xxxxxxxx, linux-xfs@xxxxxxxxxxx
Subject: Re: [RFC] Badness in __mutex_unlock_slowpath with XFS stress tests
From: Suparna Bhattacharya <suparna@xxxxxxxxxx>
Date: Tue, 14 Mar 2006 10:16:00 +0530
In-reply-to: <20060310154925.GA5339@xxxxxxxxxxxxx>
References: <440FDF3E.8060400@xxxxxxxxxx> <20060309120306.GA26682@xxxxxxxxxxxxx> <20060309223042.GC1135@frodo> <20060309224219.GA6709@xxxxxxxxxxxxx> <20060309231422.GD1135@frodo> <20060310005020.GF1135@frodo> <20060310154925.GA5339@xxxxxxxxxxxxx>
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On Fri, Mar 10, 2006 at 03:49:25PM +0000, Christoph Hellwig wrote:
> On Fri, Mar 10, 2006 at 11:50:20AM +1100, Nathan Scott wrote:
> > Something like this (works OK for me)...
> 
> Yeah, that should work for now.  But long-term we really need to redo
> direct I/O locking to have a common scheme for all filesystems.  I've heard
> birds whistling RH patches yet another scheme into RHEL4 for GFS an it's
> definitly already far too complex now.

Yup, getting rid of the need for all these confusing locking
modes was one of the objectives in mind for DIO simplification.
(http://www.kernel.org/pub/linux/kernel/people/suparna/DIO-simplify.txt)
Once we have an efficient range locking or similar mechanism in place
(Chris Mason is working on a patch), then it should be possible to push
out all of the i_mutex locking to higher level routines, outside of
direct-io.c.

Longer term, it would be nice to be able to rethink and further simplify
the whole _nolock equiv versions for VFS write methods. Especially the
percolation down to sync_page_range_nolock, etc.

Regards
Suparna

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-- 
Suparna Bhattacharya (suparna@xxxxxxxxxx)
Linux Technology Center
IBM Software Lab, India


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