Re: [RFC] Ext3 online defrag

Russell Cattelan
2006-10-24T20:32:48Z

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On Tue, 2006-10-24 at 15:44 -0400, Theodore Tso wrote:
> On Tue, Oct 24, 2006 at 11:59:28PM +1000, David Chinner wrote:
> > That's the wrong way to look at it. if you want the userspace
> > process to specify a location, then you should preallocate it first
> > before doing anything else. There is no need to clutter a simple
> > data mover interface with all sorts of unnecessary error handling.
>
> This is doable, but it adds a huge amount of complexity before we
> could implement on-line defragmentation.
>
> First of all, we would need a way of allowing userpsace to specify
> which blocks should be used in the preallocation.
>
> Secondly, we would need a way of marking blocks as "preallocated but
> not pre-zeroed"; otherwise we would have to zero out all of the blocks
> in order to assure security (don't want userspace programs seeing the
> previous contents of the data blocks), only to do the copy and the
> extents vector swap

Chris Mason page place holder work for DIRECT IO should be applicable to
any pre-allocations?

--
Russell Cattelan <cattelan@thebarn.com>

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