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Subject[PATCH 10/10] cgroup: implement cgroup_rm_cftypes()
Date
Implement cgroup_rm_cftypes() which removes an array of cftypes from a
subsystem. It can be called whether the target subsys is attached or
not. cgroup core will remove the specified file from all existing
cgroups.

This will be used to improve sub-subsys modularity and will be helpful
for unified hierarchy.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/cgroup.h | 1 +
kernel/cgroup.c | 54 +++++++++++++++++++++++++++++++++++++++--------
2 files changed, 45 insertions(+), 10 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index caeaafc..4f3a68b 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -415,6 +415,7 @@ struct cgroup_scanner {
};

int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts);
+int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts);

int cgroup_is_removed(const struct cgroup *cgrp);

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c0c61b9..cf7b298 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2698,17 +2698,20 @@ out:
return error;
}

-static int cgroup_add_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
- const struct cftype cfts[])
+static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
+ const struct cftype cfts[], bool is_add)
{
const struct cftype *cft;
int err, ret = 0;

for (cft = cfts; cft->name[0] != '\0'; cft++) {
- err = cgroup_add_file(cgrp, subsys, cft);
+ if (is_add)
+ err = cgroup_add_file(cgrp, subsys, cft);
+ else
+ err = cgroup_rm_file(cgrp, cft);
if (err) {
- pr_warning("cgroup_add_files: failed to create %s, err=%d\n",
- cft->name, err);
+ pr_warning("cgroup_addrm_files: failed to %s %s, err=%d\n",
+ is_add ? "add" : "remove", cft->name, err);
ret = err;
}
}
@@ -2732,7 +2735,7 @@ static void cgroup_cfts_prepare(void)
}

static void cgroup_cfts_commit(struct cgroup_subsys *ss,
- const struct cftype *cfts)
+ const struct cftype *cfts, bool is_add)
__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
{
LIST_HEAD(pending);
@@ -2758,7 +2761,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss,
mutex_lock(&inode->i_mutex);
mutex_lock(&cgroup_mutex);
if (!cgroup_is_removed(cgrp))
- cgroup_add_files(cgrp, ss, cfts);
+ cgroup_addrm_files(cgrp, ss, cfts, is_add);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);

@@ -2796,13 +2799,44 @@ int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)

cgroup_cfts_prepare();
list_add_tail(&set->node, &ss->cftsets);
- cgroup_cfts_commit(ss, cfts);
+ cgroup_cfts_commit(ss, cfts, true);

return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_cftypes);

/**
+ * cgroup_rm_cftypes - remove an array of cftypes from a subsystem
+ * @ss: target cgroup subsystem
+ * @cfts: zero-length name terminated array of cftypes
+ *
+ * Unregister @cfts from @ss. Files described by @cfts are removed from
+ * all existing cgroups to which @ss is attached and all future cgroups
+ * won't have them either. This function can be called anytime after
+ * subsys_initcall whether @ss is attached or not.
+ *
+ * Returns 0 on successful unregistration, -ENOENT if @cfts is not
+ * registered with @ss.
+ */
+int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
+{
+ struct cftype_set *set;
+
+ cgroup_cfts_prepare();
+
+ list_for_each_entry(set, &ss->cftsets, node) {
+ if (set->cfts == cfts) {
+ list_del_init(&set->node);
+ cgroup_cfts_commit(ss, cfts, false);
+ return 0;
+ }
+ }
+
+ cgroup_cfts_commit(ss, NULL, false);
+ return -ENOENT;
+}
+
+/**
* cgroup_task_count - count the number of tasks in a cgroup.
* @cgrp: the cgroup in question
*
@@ -3794,7 +3828,7 @@ static int cgroup_populate_dir(struct cgroup *cgrp)
int err;
struct cgroup_subsys *ss;

- err = cgroup_add_files(cgrp, NULL, files);
+ err = cgroup_addrm_files(cgrp, NULL, files, true);
if (err < 0)
return err;

@@ -3806,7 +3840,7 @@ static int cgroup_populate_dir(struct cgroup *cgrp)
return err;

list_for_each_entry(set, &ss->cftsets, node)
- cgroup_add_files(cgrp, ss, set->cfts);
+ cgroup_addrm_files(cgrp, ss, set->cfts, true);
}

/* This cgroup is ready now */
--
1.7.7.3


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