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Subject[PATCH 3/6] cgroup: add 'root' parameter to cgroup_path function
Date
This patch adds 'root' parameter to 'cgroup_path' function. When it's
not NULL creating cgroup path will stop when current cgroup is 'root'.
A task contained in cgroup isolation root will see its cgroup in
/proc/$PID/cgroup with isolation root as top.

Signed-off-by: Witold Krecicki <wpk@culm.net>
---
block/blk-cgroup.c | 2 +-
include/linux/cgroup.h | 3 ++-
kernel/cgroup.c | 16 ++++++++++++----
kernel/cpuset.c | 2 +-
kernel/sched_debug.c | 2 +-
mm/memcontrol.c | 6 +++---
6 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b596e54..2dd96e7 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -491,7 +491,7 @@ void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
blkg->plid = plid;
spin_unlock_irqrestore(&blkcg->lock, flags);
/* Need to take css reference ? */
- cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
+ cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path), NULL);
blkg->dev = dev;
}
EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 6965591..3b36554 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -436,7 +436,8 @@ int cgroup_add_files(struct cgroup *cgrp,

int cgroup_is_removed(const struct cgroup *cgrp);

-int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
+int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen,
+ const struct cgroup *root);

int cgroup_task_count(const struct cgroup *cgrp);

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0177472..f9b4bdf 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1716,12 +1716,14 @@ static inline struct cftype *__d_cft(struct dentry *dentry)
* @cgrp: the cgroup in question
* @buf: the buffer to write the path into
* @buflen: the length of the buffer
+ * @root: root cgroup for isolation
*
* Called with cgroup_mutex held or else with an RCU-protected cgroup
* reference. Writes path of cgroup into buf. Returns 0 on success,
* -errno on error.
*/
-int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
+int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen,
+ const struct cgroup *root)
{
char *start;
struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
@@ -1740,6 +1742,10 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)

*--start = '\0';
for (;;) {
+ if (cgrp == root) {
+ *start = '/';
+ break;
+ }
int len = dentry->d_name.len;

if ((start -= len) < buf)
@@ -4459,7 +4465,7 @@ static int proc_cgroup_show(struct seq_file *m, void *v)

for_each_active_root(root) {
struct cgroup_subsys *ss;
- struct cgroup *cgrp;
+ struct cgroup *cgrp, *asking_cgrp, *isol_root_cgrp;
int count = 0;

seq_printf(m, "%d:", root->hierarchy_id);
@@ -4470,7 +4476,9 @@ static int proc_cgroup_show(struct seq_file *m, void *v)
root->name);
seq_putc(m, ':');
cgrp = task_cgroup_from_root(tsk, root);
- retval = cgroup_path(cgrp, buf, PAGE_SIZE);
+ asking_cgrp = task_cgroup_from_root(current, root);
+ isol_root_cgrp = cgroup_get_isolation_root(asking_cgrp);
+ retval = cgroup_path(cgrp, buf, PAGE_SIZE, isol_root_cgrp);
if (retval < 0)
goto out_unlock;
seq_puts(m, buf);
@@ -4790,7 +4798,7 @@ static void cgroup_release_agent(struct work_struct *work)
pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!pathbuf)
goto continue_free;
- if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0)
+ if (cgroup_path(cgrp, pathbuf, PAGE_SIZE, NULL) < 0)
goto continue_free;
agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
if (!agentbuf)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 10131fd..6206a5c 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2583,7 +2583,7 @@ static int proc_cpuset_show(struct seq_file *m, void *unused_v)
retval = -EINVAL;
cgroup_lock();
css = task_subsys_state(tsk, cpuset_subsys_id);
- retval = cgroup_path(css->cgroup, buf, PAGE_SIZE);
+ retval = cgroup_path(css->cgroup, buf, PAGE_SIZE, NULL);
if (retval < 0)
goto out_unlock;
seq_puts(m, buf);
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index a6710a1..bdd8e9a 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -103,7 +103,7 @@ static char *task_group_path(struct task_group *tg)
group_path[0] = '\0';
return group_path;
}
- cgroup_path(tg->css.cgroup, group_path, PATH_MAX);
+ cgroup_path(tg->css.cgroup, group_path, PATH_MAX, NULL);
return group_path;
}
#endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3508777..6e5b35e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1388,7 +1388,7 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
mem_cgrp = memcg->css.cgroup;
task_cgrp = task_cgroup(p, mem_cgroup_subsys_id);

- ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
+ ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX, NULL);
if (ret < 0) {
/*
* Unfortunately, we are unable to convert to a useful name
@@ -1402,7 +1402,7 @@ void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
printk(KERN_INFO "Task in %s killed", memcg_name);

rcu_read_lock();
- ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
+ ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX, NULL);
if (ret < 0) {
rcu_read_unlock();
goto done;
@@ -3390,7 +3390,7 @@ void mem_cgroup_print_bad_page(struct page *page)
if (path) {
rcu_read_lock();
ret = cgroup_path(pc->mem_cgroup->css.cgroup,
- path, PATH_MAX);
+ path, PATH_MAX, NULL);
rcu_read_unlock();
}

--
1.7.4.1


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