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cgroup: factor out cgroup_{apply|finalize}_control() from cgroup_subtree_control_write()

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Factor out cgroup_{apply|finalize}_control() so that control mask
update can be done in several simple steps.  This patch doesn't
introduce behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Zefan Li <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2016-03-03 09:58:00 -05:00
parent 15a27c362d
commit f7b2814bb9
1 changed files with 58 additions and 23 deletions
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81
kernel/cgroup.c
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@ -3169,6 +3169,62 @@ static void cgroup_apply_control_disable(struct cgroup *cgrp)
}
}
/**
* cgroup_apply_control - apply control mask updates to the subtree
* @cgrp: root of the target subtree
*
* subsystems can be enabled and disabled in a subtree using the following
* steps.
*
* 1. Call cgroup_save_control() to stash the current state.
* 2. Update ->subtree_control masks in the subtree as desired.
* 3. Call cgroup_apply_control() to apply the changes.
* 4. Optionally perform other related operations.
* 5. Call cgroup_finalize_control() to finish up.
*
* This function implements step 3 and propagates the mask changes
* throughout @cgrp's subtree, updates csses accordingly and perform
* process migrations.
*/
static int cgroup_apply_control(struct cgroup *cgrp)
{
int ret;
cgroup_propagate_control(cgrp);
ret = cgroup_apply_control_enable(cgrp);
if (ret)
return ret;
/*
* At this point, cgroup_e_css() results reflect the new csses
* making the following cgroup_update_dfl_csses() properly update
* css associations of all tasks in the subtree.
*/
ret = cgroup_update_dfl_csses(cgrp);
if (ret)
return ret;
return 0;
}
/**
* cgroup_finalize_control - finalize control mask update
* @cgrp: root of the target subtree
* @ret: the result of the update
*
* Finalize control mask update. See cgroup_apply_control() for more info.
*/
static void cgroup_finalize_control(struct cgroup *cgrp, int ret)
{
if (ret) {
cgroup_restore_control(cgrp);
cgroup_propagate_control(cgrp);
}
cgroup_apply_control_disable(cgrp);
}
/* change the enabled child controllers for a cgroup in the default hierarchy */
static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
char *buf, size_t nbytes,
@ -3264,36 +3320,15 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
cgrp->subtree_control |= enable;
cgrp->subtree_control &= ~disable;
cgroup_propagate_control(cgrp);
ret = cgroup_apply_control(cgrp);
ret = cgroup_apply_control_enable(cgrp);
if (ret)
goto err_undo_css;
/*
* At this point, cgroup_e_css() results reflect the new csses
* making the following cgroup_update_dfl_csses() properly update
* css associations of all tasks in the subtree.
*/
ret = cgroup_update_dfl_csses(cgrp);
if (ret)
goto err_undo_css;
/* all tasks are migrated out of disabled csses, commit disable */
cgroup_apply_control_disable(cgrp);
cgroup_finalize_control(cgrp, ret);
kernfs_activate(cgrp->kn);
ret = 0;
out_unlock:
cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
err_undo_css:
/* restore masks and shoot down new csses */
cgroup_restore_control(cgrp);
cgroup_apply_control_disable(cgrp);
goto out_unlock;
}
static int cgroup_events_show(struct seq_file *seq, void *v)