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Date: Wed, 13 May 2009 19:41:22 -0500
From: Eric Sandeen <sandeen@sandeen.net>
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Subject: Re: file preallocation without unwritten flag being set
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To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com

Dave Chinner wrote:

>> Unmounting will flush the filesytem address space, but not the block
>> device address space.
> 
> Not exactly the problem, though. XFS opens it's own device address space
> when mounting - not the address space you get by opening /dev/sdX.
> xfs_db uses the address space associated with /dev/sdX. hence
> if you do:
> 
> # xfs_db /dev/sdc
> ....
> # mount /dev/sdc
> <do some changes>
> # unmount /dev/sdc
> # xfs_db /dev/sdc
> 
> The second invocation of xfs_db will not see any of the changes that
> occured to the filesystem because it will read from the buffers
> cached on /dev/sdc during the first invocation.
> 
> This is the same problem Grub has....

We meant the same thing, even if I said it wrong ;)

-Eric

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