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blkcg: reduce stack usage of blkg_rwstat_recursive_sum() 

The recent percpu conversion of blkg_rwstat triggered the following
warning in certain configurations.

 block/blk-cgroup.c:654:1: warning: the frame size of 1360 bytes is larger than 1024 bytes

This is because blkg_rwstat now contains four percpu_counter which can
be pretty big depending on debug options although it shouldn't be a
problem in production configs.  This patch removes one of the two
local blkg_rwstat variables used by blkg_rwstat_recursive_sum() to
reduce stack usage.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Link: http://article.gmane.org/gmane.linux.kernel.cgroups/13835
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2015-08-18 14:55:26 -07:00 committed by Jens Axboe
parent 702747cabe
commit 3a7faeada2
1 changed files with 4 additions and 6 deletions
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8
block/blk-cgroup.c
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@ -744,7 +744,7 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
rcu_read_lock(); rcu_read_lock();
blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) { blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
struct blkg_rwstat *rwstat, tmp; struct blkg_rwstat *rwstat;
if (!pos_blkg->online) if (!pos_blkg->online)
continue; continue;
@ -754,11 +754,9 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
else else
rwstat = (void *)pos_blkg + off; rwstat = (void *)pos_blkg + off;
tmp = blkg_rwstat_read(rwstat);
for (i = 0; i < BLKG_RWSTAT_NR; i++) for (i = 0; i < BLKG_RWSTAT_NR; i++)
atomic64_add(atomic64_read(&tmp.aux_cnt[i]) + atomic64_add(atomic64_read(&rwstat->aux_cnt[i]) +
atomic64_read(&rwstat->aux_cnt[i]), percpu_counter_sum_positive(&rwstat->cpu_cnt[i]),
&sum.aux_cnt[i]); &sum.aux_cnt[i]);
} }
rcu_read_unlock(); rcu_read_unlock();