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Commit 7da11279 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 5d22444f

include/linux/cgroup.h

+33 −0
Original line number Diff line number Diff line
@@ -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);

kernel/cgroup.c

+20 −30
Original line number Diff line number Diff line
@@ -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 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *userbuf, 


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;

	}

}