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Groups > linux.kernel > #1340215

[PATCH 02/12] cgroup: explicitly track whether a cgroup_subsys_state is visible to userland

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Currently, whether a css (cgroup_subsys_state) has its interface files
created is not tracked and assumed to change together with the owning
cgroup's lifecycle.  cgroup directory and interface creation is being
separated out from internal object creation to help refactoring and
eventually allow cgroups which are not visible through cgroupfs.

This patch adds CSS_VISIBLE to track whether a css has its interface
files created and perform management operations only when necessary
which helps decoupling interface file handling from internal object
lifecycle.  After this patch, all css interface file management
functions can be called regardless of the current state and will
achieve the expected result.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 include/linux/cgroup-defs.h |  1 +
 kernel/cgroup.c             | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 0abf6aa..13a2708 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -45,6 +45,7 @@ enum {
 	CSS_NO_REF	= (1 << 0), /* no reference counting for this css */
 	CSS_ONLINE	= (1 << 1), /* between ->css_online() and ->css_offline() */
 	CSS_RELEASED	= (1 << 2), /* refcnt reached zero, released */
+	CSS_VISIBLE	= (1 << 3), /* css is visible to userland */
 };
 
 /* bits in struct cgroup flags field */
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 48ea999..9e5caf0 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1420,6 +1420,11 @@ static void css_clear_dir(struct cgroup_subsys_state *css,
 	struct cgroup *cgrp = cgrp_override ?: css->cgroup;
 	struct cftype *cfts;
 
+	if (!(css->flags & CSS_VISIBLE))
+		return;
+
+	css->flags &= ~CSS_VISIBLE;
+
 	list_for_each_entry(cfts, &css->ss->cfts, node)
 		cgroup_addrm_files(css, cgrp, cfts, false);
 }
@@ -1438,6 +1443,9 @@ static int css_populate_dir(struct cgroup_subsys_state *css,
 	struct cftype *cfts, *failed_cfts;
 	int ret;
 
+	if (css->flags & CSS_VISIBLE)
+		return 0;
+
 	if (!css->ss) {
 		if (cgroup_on_dfl(cgrp))
 			cfts = cgroup_dfl_base_files;
@@ -1454,6 +1462,9 @@ static int css_populate_dir(struct cgroup_subsys_state *css,
 			goto err;
 		}
 	}
+
+	css->flags |= CSS_VISIBLE;
+
 	return 0;
 err:
 	list_for_each_entry(cfts, &css->ss->cfts, node) {
@@ -3402,7 +3413,7 @@ static int cgroup_apply_cftypes(struct cftype *cfts, bool is_add)
 	css_for_each_descendant_pre(css, cgroup_css(root, ss)) {
 		struct cgroup *cgrp = css->cgroup;
 
-		if (cgroup_is_dead(cgrp))
+		if (!(css->flags & CSS_VISIBLE))
 			continue;
 
 		ret = cgroup_addrm_files(css, cgrp, cfts, is_add);
-- 
2.5.0

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[PATCHSET cgroup/for-4.6] cgroup: make control mask updates modular and recursive Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 03/12] cgroup: reorder operations in cgroup_mkdir() Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 08/12] cgroup: factor out cgroup_apply_control_enable() from cgroup_subtree_control_write() Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 05/12] cgroup: introduce cgroup_control() and cgroup_ss_mask() Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 04/12] cgroup: factor out cgroup_create() out of cgroup_mkdir() Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 06/12] cgroup: factor out cgroup_drain_offline() from cgroup_subtree_control_write() Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 02/12] cgroup: explicitly track whether a cgroup_subsys_state is visible to userland Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 10/12] cgroup: introduce cgroup_{save|propagate|restore}_control() Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 01/12] cgroup: separate out interface file creation from css creation Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100
  [PATCH 09/12] cgroup: make cgroup_drain_offline() and cgroup_apply_control_{disable|enable}() recursive Tejun Heo <tj@kernel.org> - 2016-02-23 04:50 +0100

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