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Re: [PATCH 6/9] xfs: disable swap extents ioctl on CRC enabled filesyste

To: Ben Myers <bpm@xxxxxxx>
Subject: Re: [PATCH 6/9] xfs: disable swap extents ioctl on CRC enabled filesystems
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 30 May 2013 11:07:21 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130528214931.GA20028@xxxxxxx>
References: <1369636707-15150-1-git-send-email-david@xxxxxxxxxxxxx> <1369636707-15150-7-git-send-email-david@xxxxxxxxxxxxx> <20130528214931.GA20028@xxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, May 28, 2013 at 04:49:31PM -0500, Ben Myers wrote:
> On Mon, May 27, 2013 at 04:38:24PM +1000, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@xxxxxxxxxx>
> > 
> > Currently, swapping extents from one inode to another is a simple
> > act of switching data and attribute forks from one inode to another.
> > This, unfortunately in no longer so simple with CRC enabled
> > filesystems as there is owner information embedded into the BMBT
> > blocks that are swapped between inodes. Hence swapping the forks
> > between inodes results in the inodes having mapping blocks that
> > point to the wrong owner and hence are considered corrupt.
> > 
> > To fix this we need an extent tree block or record based swap
> > algorithm so that the BMBT block owner information can be updated
> > atomically in the swap transaction. This is a significant piece of
> > new work, so for the moment simply don't allow swap extent
> > operations to succeed on CRC enabled filesystems.
> > 
> > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> I believe we do want to have functional swap extents for crc enabled
> filesystems.

Of course.

> But this is fine as long as it is temporary.

It is.


Dave Chinner

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