From ef56578274d2b98423c8ef82bb450223f5811b59 Mon Sep 17 00:00:00 2001 From: Michal Koutný Date: Wed, 7 Jan 2026 17:59:41 +0100 Subject: cgroup: Eliminate cgrp_ancestor_storage in cgroup_root MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The cgrp_ancestor_storage has two drawbacks: - it's not guaranteed that the member immediately follows struct cgrp in cgroup_root (root cgroup's ancestors[0] might thus point to a padding and not in cgrp_ancestor_storage proper), - this idiom raises warnings with -Wflex-array-member-not-at-end. Instead of relying on the auxiliary member in cgroup_root, define the 0-th level ancestor inside struct cgroup (needed for static allocation of cgrp_dfl_root), deeper cgroups would allocate flexible _low_ancestors[]. Unionized alias through ancestors[] will transparently join the two ranges. The above change would still leave the flexible array at the end of struct cgroup inside cgroup_root, so move cgrp also towards the end of cgroup_root to resolve the -Wflex-array-member-not-at-end. Link: https://lore.kernel.org/r/5fb74444-2fbb-476e-b1bf-3f3e279d0ced@embeddedor.com/ Reported-by: Gustavo A. R. Silva Closes: https://lore.kernel.org/r/b3eb050d-9451-4b60-b06c-ace7dab57497@embeddedor.com/ Cc: David Laight Acked-by: Gustavo A. R. Silva Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index e717208cfb18..554a02ee298b 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5847,7 +5847,7 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name, int ret; /* allocate the cgroup and its ID, 0 is reserved for the root */ - cgrp = kzalloc(struct_size(cgrp, ancestors, (level + 1)), GFP_KERNEL); + cgrp = kzalloc(struct_size(cgrp, _low_ancestors, level), GFP_KERNEL); if (!cgrp) return ERR_PTR(-ENOMEM); -- cgit v1.2.3