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cgroup: attach cgroup_open_file to all cgroup files

Browse source 
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 <[email protected]>
Acked-by: Li Zefan <[email protected]>
This commit is contained in:
Tejun Heo 2013-12-05 12:28:04 -05:00
commit 7da1127927
2 changed files with 53 additions and 30 deletions
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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;
}
}