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[V4,07/12] cgroup: export fhandle info for a cgroup

Message ID a81d74a4e19be95207d7455ec9abb4fb0b4d1736.1498666964.git.shli@fb.com (mailing list archive)
State New, archived
Headers show

Commit Message

Shaohua Li June 28, 2017, 4:29 p.m. UTC 
From: Shaohua Li <shli@fb.com>

Add an API to export cgroup fhandle info. We don't export a full 'struct
file_handle', there are unrequired info. Sepcifically, cgroup is always
a directory, so we don't need a 'FILEID_INO32_GEN_PARENT' type fhandle,
we only need export the inode number and generation number just like
what generic_fh_to_dentry does. And we can avoid the overhead of getting
an inode too, since kernfs_node_id (ino and generation) has all the info
required.

Signed-off-by: Shaohua Li <shli@fb.com>
---
 include/linux/cgroup.h | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Tejun Heo June 28, 2017, 6:12 p.m. UTC | #1 
On Wed, Jun 28, 2017 at 09:29:57AM -0700, Shaohua Li wrote:
> From: Shaohua Li <shli@fb.com>
> 
> Add an API to export cgroup fhandle info. We don't export a full 'struct
> file_handle', there are unrequired info. Sepcifically, cgroup is always
> a directory, so we don't need a 'FILEID_INO32_GEN_PARENT' type fhandle,
> we only need export the inode number and generation number just like
> what generic_fh_to_dentry does. And we can avoid the overhead of getting
> an inode too, since kernfs_node_id (ino and generation) has all the info
> required.
> 
> Signed-off-by: Shaohua Li <shli@fb.com>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.
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Patch

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 30c6877..52ef9a6 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -609,6 +609,10 @@  static inline void cgroup_kthread_ready(void)
 	current->no_cgroup_migration = 0;
 }
 
+static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp)
+{
+	return &cgrp->kn->id;
+}
 #else /* !CONFIG_CGROUPS */
 
 struct cgroup_subsys_state;
@@ -631,6 +635,10 @@  static inline int cgroup_init_early(void) { return 0; }
 static inline int cgroup_init(void) { return 0; }
 static inline void cgroup_init_kthreadd(void) {}
 static inline void cgroup_kthread_ready(void) {}
+static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp)
+{
+	return NULL;
+}
 
 static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
 					       struct cgroup *ancestor)