[Tux3] Extent support has landed

[Daniel Phillips]

On Friday 03 October 2008 09:03, I wrote:
> Once we have the extent, we probe into the btree, 64 blocks below the 
> beginning of the extent, which ensures that no existing extents that 
> may overlap the io extent are missed...

...and I should mention, this constitutes a small efficiency that can be 
easily corrected.  Each btree leaf pointer simply needs to have a bit 
reserved to indicate that some extents may overlap into the next btree 
leaf, and we check that bit during the probe to determine whether to 
seek directly to the target extent address, or to the predecessor node.

This is the strategy used by HTree, and is one of the unique elements of 
HTree that distinquishes it from a standard BTree.  This "continuation" 
bit is to be implmented in the generic btree code so that all the Tux3 
btree flavors can take advantage of it, and therefore will be a step in 
the direction of implementing HTree and PHTree for tux3.

Regards,

Daniel

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