tree cd4d643bfbd37c67ff9bd2feff2c0b477a56f117
parent 64769240bd07f446f83660bb143bb609d8ab4910
author Mingming Cao <cmm@us.ibm.com> 1215818851 -0400
committer Theodore Ts'o <tytso@mit.edu> 1215818851 -0400

percpu_counter: new function percpu_counter_sum_and_set

Delayed allocation need to check free blocks at every write time.
percpu_counter_read_positive() is not quit accurate. delayed
allocation need a more accurate accounting, but using
percpu_counter_sum_positive() is frequently is quite expensive.

This patch added a new function to update center counter when sum
per-cpu counter, to increase the accurate rate for next
percpu_counter_read() and require less calling expensive
percpu_counter_sum().

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>