Attached is a small test program that exposes the regression.

Kernel LEADING_EMPTY_SPACE wall-clock time to run
2.6.15    0                0.2s
2.6.15    1                29.3s
2.6.14.7  0                0.2s
2.6.14.7  1                0.2s

So it seems that if a file is repeatedly read from and written to, it
matters a lot for later kernels whether or not the blocks that are
worked on, are offset a single byte or not...

Any ideas?

-- 

 / jakob