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由 Tejun Heo 提交于
A cgroup which is already a threaded domain may be converted into a threaded cgroup if the prerequisite conditions are met. When this happens, all threaded descendant should also have their ->dom_cgrp updated to the new threaded domain cgroup. Unfortunately, this propagation was missing leading to the following failure. # cd /sys/fs/cgroup/unified # cat cgroup.subtree_control # show that no controllers are enabled # mkdir -p mycgrp/a/b/c # echo threaded > mycgrp/a/b/cgroup.type At this point, the hierarchy looks as follows: mycgrp [d] a [dt] b [t] c [inv] Now let's make node "a" threaded (and thus "mycgrp" s made "domain threaded"): # echo threaded > mycgrp/a/cgroup.type By this point, we now have a hierarchy that looks as follows: mycgrp [dt] a [t] b [t] c [inv] But, when we try to convert the node "c" from "domain invalid" to "threaded", we get ENOTSUP on the write(): # echo threaded > mycgrp/a/b/c/cgroup.type sh: echo: write error: Operation not supported This patch fixes the problem by * Moving the opencoded ->dom_cgrp save and restoration in cgroup_enable_threaded() into cgroup_{save|restore}_control() so that mulitple cgroups can be handled. * Updating all threaded descendants' ->dom_cgrp to point to the new dom_cgrp when enabling threaded mode. Signed-off-by: NTejun Heo <tj@kernel.org> Reported-and-tested-by: N"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> Reported-by: NAmin Jamali <ajamali@pivotal.io> Reported-by: NJoao De Almeida Pereira <jpereira@pivotal.io> Link: https://lore.kernel.org/r/CAKgNAkhHYCMn74TCNiMJ=ccLd7DcmXSbvw3CbZ1YREeG7iJM5g@mail.gmail.com Fixes: 454000ad ("cgroup: introduce cgroup->dom_cgrp and threaded css_set handling") Cc: stable@vger.kernel.org # v4.14+
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