-/*
- * Atomically mark all (or else none) of the cgroup's CSS objects as
- * CSS_REMOVED. Return true on success, or false if the cgroup has
- * busy subsystems. Call with cgroup_mutex held
- *
- * Depending on whether a subsys has __DEPRECATED_clear_css_refs set or
- * not, cgroup removal behaves differently.
- *
- * If clear is set, css refcnt for the subsystem should be zero before
- * cgroup removal can be committed. This is implemented by
- * CGRP_WAIT_ON_RMDIR and retry logic around ->pre_destroy(), which may be
- * called multiple times until all css refcnts reach zero and is allowed to
- * veto removal on any invocation. This behavior is deprecated and will be
- * removed as soon as the existing user (memcg) is updated.
- *
- * If clear is not set, each css holds an extra reference to the cgroup's
- * dentry and cgroup removal proceeds regardless of css refs.
- * ->pre_destroy() will be called at least once and is not allowed to fail.
- * On the last put of each css, whenever that may be, the extra dentry ref
- * is put so that dentry destruction happens only after all css's are
- * released.
- */
-static int cgroup_clear_css_refs(struct cgroup *cgrp)
-{
- struct cgroup_subsys *ss;
- unsigned long flags;
- bool failed = false;
-
- local_irq_save(flags);
-
- /*
- * Block new css_tryget() by deactivating refcnt. If all refcnts
- * for subsystems w/ clear_css_refs set were 1 at the moment of
- * deactivation, we succeeded.
- */
- for_each_subsys(cgrp->root, ss) {
- struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
-
- WARN_ON(atomic_read(&css->refcnt) < 0);
- atomic_add(CSS_DEACT_BIAS, &css->refcnt);
-
- if (ss->__DEPRECATED_clear_css_refs)
- failed |= css_refcnt(css) != 1;
- }
-
- /*
- * If succeeded, set REMOVED and put all the base refs; otherwise,
- * restore refcnts to positive values. Either way, all in-progress
- * css_tryget() will be released.
- */
- for_each_subsys(cgrp->root, ss) {
- struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
-
- if (!failed) {
- set_bit(CSS_REMOVED, &css->flags);
- css_put(css);
- } else {
- atomic_sub(CSS_DEACT_BIAS, &css->refcnt);
- }
- }
-
- local_irq_restore(flags);
- return !failed;
-}
-