cgroups: fix API thinko
Add cgroup_attach_task_all() The existing cgroup_attach_task_current_cg() API is called by a thread to attach another thread to all of its cgroups; this is unsuitable for cases where a privileged task wants to attach itself to the cgroups of a less privileged one, since the call must be made from the context of the target task. This patch adds a more generic cgroup_attach_task_all() API that allows both the source task and to-be-moved task to be specified. cgroup_attach_task_current_cg() becomes a specialization of the more generic new function. [menage@google.com: rewrote changelog] [akpm@linux-foundation.org: address reviewer comments] Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Tested-by: Alex Williamson <alex.williamson@redhat.com> Acked-by: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Ben Blum <bblum@google.com> Cc: Sridhar Samudrala <sri@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -578,7 +578,12 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
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void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
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int cgroup_scan_tasks(struct cgroup_scanner *scan);
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int cgroup_attach_task(struct cgroup *, struct task_struct *);
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int cgroup_attach_task_current_cg(struct task_struct *);
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int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
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static inline int cgroup_attach_task_current_cg(struct task_struct *tsk)
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{
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return cgroup_attach_task_all(current, tsk);
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}
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/*
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* CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
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@ -636,6 +641,11 @@ static inline int cgroupstats_build(struct cgroupstats *stats,
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}
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/* No cgroups - nothing to do */
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static inline int cgroup_attach_task_all(struct task_struct *from,
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struct task_struct *t)
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{
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return 0;
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}
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static inline int cgroup_attach_task_current_cg(struct task_struct *t)
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{
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return 0;
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@ -1791,19 +1791,20 @@ out:
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}
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/**
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* cgroup_attach_task_current_cg - attach task 'tsk' to current task's cgroup
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* cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
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* @from: attach to all cgroups of a given task
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* @tsk: the task to be attached
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*/
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int cgroup_attach_task_current_cg(struct task_struct *tsk)
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int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
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{
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struct cgroupfs_root *root;
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struct cgroup *cur_cg;
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int retval = 0;
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cgroup_lock();
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for_each_active_root(root) {
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cur_cg = task_cgroup_from_root(current, root);
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retval = cgroup_attach_task(cur_cg, tsk);
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struct cgroup *from_cg = task_cgroup_from_root(from, root);
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retval = cgroup_attach_task(from_cg, tsk);
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if (retval)
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break;
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}
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@ -1811,7 +1812,7 @@ int cgroup_attach_task_current_cg(struct task_struct *tsk)
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return retval;
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}
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EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg);
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EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
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/*
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* Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
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