How does VOP_BMAP() handle fragments?

Given a file with holes obtained from ftruncate(), what does VOP_BMAP()
return in its argument "bnp" if it finds a fragment?

Is it the block number of the fragment or will it return (daddr_t)-1?

Is it always ok to write a full block to "bnp"?
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Juergen Hannken-Illjes - hannken@eis.cs.tu-bs.de - TU Braunschweig (Germany)