linux-ext4 - Re: [RFC PATCH] ext4: Use page_mkwrite vma_operations to get mmap write notification.

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Message-ID: <20080305235941.GD18188@mit.edu>
Date:	Wed, 5 Mar 2008 18:59:41 -0500
From:	Theodore Tso <tytso@....EDU>
To:	Mingming Cao <cmm@...ibm.com>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-ext4@...r.kernel.org
Subject: Re: [RFC PATCH] ext4: Use page_mkwrite vma_operations to get mmap
	write notification.

On Wed, Mar 05, 2008 at 03:37:18PM -0800, Mingming Cao wrote:
> On Wed, 2008-03-05 at 18:29 -0500, Theodore Tso wrote:
> > On Tue, Mar 04, 2008 at 04:45:51PM -0800, Mingming Cao wrote:
> > > > +	/* FIXME!! should we take inode->i_mutex ? Currently we can't because
> > > > +	 * it has a circular locking dependency with DIO. But migrate expect
> > > > +	 * i_mutex to ensure no i_data changes
> > 
> > Should I worry that we have something in the stable part of the patch
> > queue with this FIXME!! comment?  :-)
> > 
> 
> I think this comment could be moved to the migration.c. We can't take
> i_mutex on mapped IO path. The i_data_mutex is the lock that should
> protect the i_data concurrent changes, which is currently mapped IO
> used. The race with migration could be addressed in migration instead of
> here. I propose we drop this comment for now.

OK, but that still means we have a known bug in the migration code,
which is in mainline....

						- Ted
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