[PATCH 0/2] xfs: fix inode count underrun

Dave Chinner
2015-05-05T22:02:24Z

Hi folks,

With the conversion of XFS to use the generic per-cpu superblocks, I
overlooked the fact that the update batch size is important to the
accuracy of the comparison function. Using different batch sizes
means percpu_counter_compare() doesn't detect when it should fall
back to percpu_counter_sum() for accuracy correctly, resulting in
counter comparisons being inaccurate. This leads to problems with
zero threshold detection in XFS.

To fix, add __percpu_counter_compare() to take a caller supplied
batch size. This fixes the XFS regression introduced in 4.1-rc1.

-Dave.