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cgroup: attach cgroup_open_file to all cgroup files

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In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs.  This patch
attaches cgroup_open_file, which used to be attached to pidlist files,
to all cgroup files, introduces seq_css/cft() accessors to determine
the cgroup_subsys_state and cftype associated with a given cgroup
seq_file, exports them as public interface.

This doesn't cause any behavior changes but unifies cgroup file
handling across different file types and will help converting them to
kernfs seq_show() interface.

v2: Li pointed out that the original patch was using
    single_open_size() incorrectly assuming that the size param is
    private data size.  Fix it by allocating @of separately and
    passing it to single_open() and explicitly freeing it in the
    release path.  This isn't the prettiest but this path is gonna be
    restructured by the following patches pretty soon.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-12-05 12:28:04 -05:00
parent 5d22444f42
commit 7da1127927
2 changed files with 53 additions and 30 deletions
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33
include/linux/cgroup.h
View file

@ -21,6 +21,7 @@
#include <linux/xattr.h>
#include <linux/fs.h>
#include <linux/percpu-refcount.h>
#include <linux/seq_file.h>
#ifdef CONFIG_CGROUPS
@ -489,6 +490,26 @@ struct cftype_set {
struct cftype *cfts;
};
/*
* cgroupfs file entry, pointed to from leaf dentry->d_fsdata. Don't
* access directly.
*/
struct cfent {
struct list_head node;
struct dentry *dentry;
struct cftype *type;
struct cgroup_subsys_state *css;
/* file xattrs */
struct simple_xattrs xattrs;
};
/* seq_file->private points to the following, only ->priv is public */
struct cgroup_open_file {
struct cfent *cfe;
void *priv;
};
/*
* See the comment above CGRP_ROOT_SANE_BEHAVIOR for details. This
* function can be called as long as @cgrp is accessible.
@ -504,6 +525,18 @@ static inline const char *cgroup_name(const struct cgroup *cgrp)
return rcu_dereference(cgrp->name)->name;
}
static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
{
struct cgroup_open_file *of = seq->private;
return of->cfe->css;
}
static inline struct cftype *seq_cft(struct seq_file *seq)
{
struct cgroup_open_file *of = seq->private;
return of->cfe->type;
}
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_rm_cftypes(struct cftype *cfts);