Commit 3a7faead authored Aug 18, 2015 by Tejun Heo Committed by Jens Axboe Aug 18, 2015

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>

parent 702747ca

block/blk-cgroup.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -744,7 +744,7 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,

		rcu_read_lock();
		blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
		struct blkg_rwstat *rwstat, tmp;
		struct blkg_rwstat *rwstat;

		if (!pos_blkg->online)
		continue;
		@@ -754,11 +754,9 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
		else
		rwstat = (void *)pos_blkg + off;

		tmp = blkg_rwstat_read(rwstat);

		for (i = 0; i < BLKG_RWSTAT_NR; i++)
		atomic64_add(atomic64_read(&tmp.aux_cnt[i]) +
		atomic64_read(&rwstat->aux_cnt[i]),
		atomic64_add(atomic64_read(&rwstat->aux_cnt[i]) +
		percpu_counter_sum_positive(&rwstat->cpu_cnt[i]),
		&sum.aux_cnt[i]);
		}
		rcu_read_unlock();

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