[PATCH v5 01/16] cgroup: Added cgroup_get_from_id

[Muneendra]

Added a new function cgroup_get_from_id  to retrieve the cgroup
associated with cgroup id.
Exported the same as this can be used by blk-cgorup.c

Added function declaration of cgroup_get_from_id in cgorup.h

This patch also exported the function cgroup_get_e_css
as this is getting used in blk-cgroup.h

Signed-off-by: Muneendra <muneendra.kumar at broadcom.com>

---
v5:
renamed the function cgroup_get_from_kernfs_id to
cgroup_get_from_id

v4:
No change

v3:
Exported the cgroup_get_e_css

v2:
New patch
---
 include/linux/cgroup.h |  6 ++++++
 kernel/cgroup/cgroup.c | 26 ++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 618838c48313..da31b14db198 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -696,6 +696,7 @@ static inline void cgroup_kthread_ready(void)
 }
 
 void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen);
+struct cgroup *cgroup_get_from_id(u64 id);
 #else /* !CONFIG_CGROUPS */
 
 struct cgroup_subsys_state;
@@ -743,6 +744,11 @@ static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
 
 static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
 {}
+
+static struct cgroup *cgroup_get_from_id(u64 id)
+{
+	return NULL;
+}
 #endif /* !CONFIG_CGROUPS */
 
 #ifdef CONFIG_CGROUPS
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index e41c21819ba0..34ebfbeba098 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -580,6 +580,7 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
 	rcu_read_unlock();
 	return css;
 }
+EXPORT_SYMBOL_GPL(cgroup_get_e_css);
 
 static void cgroup_get_live(struct cgroup *cgrp)
 {
@@ -5805,6 +5806,31 @@ void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
 	kernfs_put(kn);
 }
 
+/*
+ * cgroup_get_from_id : get the cgroup associated with cgroup id
+ * @id: cgroup id
+ * On success it returns the cgrp on failure it returns NULL
+ */
+struct cgroup *cgroup_get_from_id(u64 id)
+{
+	struct kernfs_node *kn;
+	struct cgroup *cgrp = NULL;
+
+	mutex_lock(&cgroup_mutex);
+	kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
+	if (!kn)
+		goto out_unlock;
+
+	cgrp = kn->priv;
+	if (cgroup_is_dead(cgrp) || !cgroup_tryget(cgrp))
+		cgrp = NULL;
+	kernfs_put(kn);
+out_unlock:
+	mutex_unlock(&cgroup_mutex);
+	return cgrp;
+}
+EXPORT_SYMBOL_GPL(cgroup_get_from_id);
+
 /*
  * proc_cgroup_show()
  *  - Print task's cgroup paths into seq_file, one line for each hierarchy
-- 
2.26.2


-- 
This electronic communication and the information and any files transmitted 
with it, or attached to it, are confidential and are intended solely for 
the use of the individual or entity to whom it is addressed and may contain 
information that is confidential, legally privileged, protected by privacy 
laws, or otherwise restricted from disclosure to anyone else. If you are 
not the intended recipient or the person responsible for delivering the 
e-mail to the intended recipient, you are hereby notified that any use, 
copying, distributing, dissemination, forwarding, printing, or copying of 
this e-mail is strictly prohibited. If you received this e-mail in error, 
please return the e-mail to the sender, delete it from your computer, and 
destroy any printed copy of it.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 4177 bytes
Desc: S/MIME Cryptographic Signature
URL: <http://lists.infradead.org/pipermail/linux-nvme/attachments/20201216/61acfd4e/attachment.p7s>