Commit 04313591 authored Mar 03, 2016 by Tejun Heo

cgroup: allocate 2x cgrp_cset_links when setting up a new root



During prep, cgroup_setup_root() allocates cgrp_cset_links matching
the number of existing css_sets to later link the new root.  This is
fine for now as the only operation which can happen inbetween is
rebind_subsystems() and rebinding of empty subsystems doesn't create
new css_sets.

However, while not yet allowed, with the recent reimplementation,
rebind_subsystems() can rebind subsystems with descendant csses and
thus can create new css_sets.  This patch makes cgroup_setup_root()
allocate 2x of the existing css_sets so that later use of live
subsystem rebinding doesn't blow up.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>

parent 5ced2518

kernel/cgroup.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -1915,10 +1915,11 @@ static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
		/*
		* We're accessing css_set_count without locking css_set_lock here,
		* but that's OK - it can only be increased by someone holding
		* cgroup_lock, and that's us. The worst that can happen is that we
		* have some link structures left over
		* cgroup_lock, and that's us. Later rebinding may disable
		* controllers on the default hierarchy and thus create new csets,
		* which can't be more than the existing ones. Allocate 2x.
		*/
		ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
		ret = allocate_cgrp_cset_links(2 * css_set_count, &tmp_links);
		if (ret)
		goto cancel_ref;

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