cgroup: start switching to fs_context

Unfortunately, cgroup is tangled into kernfs infrastructure.
To avoid converting all kernfs-based filesystems at once,
we need to untangle the remount part of things, instead of
having it go through kernfs_sop_remount_fs().  Fortunately,
it's not hard to do.

This commit just gets cgroup/cgroup1 to use fs_context to
deliver options on mount and remount paths.  Parsing those
is going to be done in the next commits; for now we do
pretty much what legacy case does.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 14 insertions, 0 deletions

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index c9a35f09e4b9..a89cb0ba7a68 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -7,6 +7,7 @@
 #include <linux/workqueue.h>
 #include <linux/list.h>
 #include <linux/refcount.h>
+#include <linux/fs_context.h>
 
 #define TRACE_CGROUP_PATH_LEN 1024
 extern spinlock_t trace_cgroup_path_lock;
@@ -37,6 +38,18 @@ extern void __init enable_debug_cgroup(void);
 	} while (0)
 
 /*
+ * The cgroup filesystem superblock creation/mount context.
+ */
+struct cgroup_fs_context {
+	char *data;
+};
+
+static inline struct cgroup_fs_context *cgroup_fc2context(struct fs_context *fc)
+{
+	return fc->fs_private;
+}
+
+/*
  * A cgroup can be associated with multiple css_sets as different tasks may
  * belong to different cgroups on different hierarchies.  In the other
  * direction, a css_set is naturally associated with multiple cgroups.
@@ -255,5 +268,6 @@ void cgroup1_check_for_release(struct cgroup *cgrp);
 struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
 			     void *data, unsigned long magic,
 			     struct cgroup_namespace *ns);
+int cgroup1_reconfigure(struct fs_context *ctx);
 
 #endif /* __CGROUP_INTERNAL_H */