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cgroup: attach cgroup_open_file to all cgroup files 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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);

50
kernel/cgroup.c
View File

@ -41,7 +41,6 @@
#include <linux/rcupdate.h>
#include <linux/sched.h>
#include <linux/backing-dev.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/spinlock.h>
@ -130,19 +129,6 @@ static struct cgroupfs_root cgroup_dummy_root;
/* dummy_top is a shorthand for the dummy hierarchy's top cgroup */
static struct cgroup * const cgroup_dummy_top = &cgroup_dummy_root.top_cgroup;
/*
* cgroupfs file entry, pointed to from leaf dentry->d_fsdata.
*/
struct cfent {
struct list_head node;
struct dentry *dentry;
struct cftype *type;
struct cgroup_subsys_state *css;
/* file xattrs */
struct simple_xattrs xattrs;
};
/* The list of hierarchy roots */
static LIST_HEAD(cgroup_roots);
@ -2302,9 +2288,8 @@ out_free:
static int cgroup_seqfile_show(struct seq_file *m, void *arg)
{
struct cfent *cfe = m->private;
struct cftype *cft = cfe->type;
struct cgroup_subsys_state *css = cfe->css;
struct cftype *cft = seq_cft(m);
struct cgroup_subsys_state *css = seq_css(m);
if (cft->read_seq_string)
return cft->read_seq_string(css, cft, m);
@ -2353,10 +2338,20 @@ static int cgroup_file_open(struct inode *inode, struct file *file)
WARN_ON_ONCE(cfe->css && cfe->css != css);
cfe->css = css;
if (cft->open)
if (cft->open) {
err = cft->open(inode, file);
else
err = single_open(file, cgroup_seqfile_show, cfe);
} else {
struct cgroup_open_file *of;
err = -ENOMEM;
of = kzalloc(sizeof(*of), GFP_KERNEL);
if (of) {
of->cfe = cfe;
err = single_open(file, cgroup_seqfile_show, of);
if (err)
kfree(of);
}
}
if (css->ss && err)
css_put(css);
@ -2370,6 +2365,7 @@ static int cgroup_file_release(struct inode *inode, struct file *file)
if (css->ss)
css_put(css);
kfree(((struct seq_file *)file->private_data)->private);
return single_release(inode, file);
}
@ -3368,12 +3364,6 @@ struct cgroup_pidlist {
struct delayed_work destroy_dwork;
};
/* seq_file->private points to the following */
struct cgroup_open_file {
struct cfent *cfe;
void *priv;
};
/*
* The following two functions "fix" the issue where there are more pids
* than kmalloc will give memory for; in such cases, we use vmalloc/vfree.
@ -3689,9 +3679,9 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
* next pid to display, if any
*/
struct cgroup_open_file *of = s->private;
struct cgroup *cgrp = of->cfe->css->cgroup;
struct cgroup *cgrp = seq_css(s)->cgroup;
struct cgroup_pidlist *l;
enum cgroup_filetype type = of->cfe->type->private;
enum cgroup_filetype type = seq_cft(s)->private;
int index = 0, pid = *pos;
int *iter, ret;
@ -3749,7 +3739,7 @@ static void cgroup_pidlist_stop(struct seq_file *s, void *v)
if (l)
mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
CGROUP_PIDLIST_DESTROY_DELAY);
mutex_unlock(&of->cfe->css->cgroup->pidlist_mutex);
mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
}
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
@ -3766,7 +3756,7 @@ static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
if (p >= end) {
return NULL;
} else {
*pos = cgroup_pid_fry(of->cfe->css->cgroup, *p);
*pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
return p;
}
}