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Commit 91796569 authored by Paul Menage's avatar Paul Menage Committed by Linus Torvalds
Browse files

CGroup API files: add cgroup map data type 



Adds a new type of supported control file representation, a map from strings
to u64 values.

Each map entry is printed as a line in a similar format to /proc/vmstat, i.e.
"$key $value\n"

Signed-off-by: default avatarPaul Menage <menage@google.com>
Cc: "Li Zefan" <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "YAMAMOTO Takashi" <yamamoto@valinux.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 700fe1ab

include/linux/cgroup.h

+19 −0
Original line number Diff line number Diff line
@@ -166,6 +166,16 @@ struct css_set { 


};



/*

 * cgroup_map_cb is an abstract callback API for reporting map-valued

 * control files

 */



struct cgroup_map_cb {

	int (*fill)(struct cgroup_map_cb *cb, const char *key, u64 value);

	void *state;

};



/* struct cftype:

 *

 * The files in the cgroup filesystem mostly have a very simple read/write
@@ -194,6 +204,15 @@ struct cftype { 
	 * single integer. Use it in place of read()

	 */

	u64 (*read_u64) (struct cgroup *cgrp, struct cftype *cft);

	/*

	 * read_map() is used for defining a map of key/value

	 * pairs. It should call cb->fill(cb, key, value) for each

	 * entry. The key/value pairs (and their ordering) should not

	 * change between reboots.

	 */

	int (*read_map) (struct cgroup *cont, struct cftype *cft,

			 struct cgroup_map_cb *cb);



	ssize_t (*write) (struct cgroup *cgrp, struct cftype *cft,

			  struct file *file,

			  const char __user *buf, size_t nbytes, loff_t *ppos);

kernel/cgroup.c

+52 −1
Original line number Diff line number Diff line
@@ -1492,6 +1492,46 @@ static ssize_t cgroup_file_read(struct file *file, char __user *buf, 
	return -EINVAL;

}



/*

 * seqfile ops/methods for returning structured data. Currently just

 * supports string->u64 maps, but can be extended in future.

 */



struct cgroup_seqfile_state {

	struct cftype *cft;

	struct cgroup *cgroup;

};



static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)

{

	struct seq_file *sf = cb->state;

	return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value);

}



static int cgroup_seqfile_show(struct seq_file *m, void *arg)

{

	struct cgroup_seqfile_state *state = m->private;

	struct cftype *cft = state->cft;

	struct cgroup_map_cb cb = {

		.fill = cgroup_map_add,

		.state = m,

	};

	return cft->read_map(state->cgroup, cft, &cb);

}



int cgroup_seqfile_release(struct inode *inode, struct file *file)

{

	struct seq_file *seq = file->private_data;

	kfree(seq->private);

	return single_release(inode, file);

}



static struct file_operations cgroup_seqfile_operations = {

	.read = seq_read,

	.llseek = seq_lseek,

	.release = cgroup_seqfile_release,

};



static int cgroup_file_open(struct inode *inode, struct file *file)

{

	int err;
@@ -1504,7 +1544,18 @@ static int cgroup_file_open(struct inode *inode, struct file *file) 
	cft = __d_cft(file->f_dentry);

	if (!cft)

		return -ENODEV;

	if (cft->open)

	if (cft->read_map) {

		struct cgroup_seqfile_state *state =

			kzalloc(sizeof(*state), GFP_USER);

		if (!state)

			return -ENOMEM;

		state->cft = cft;

		state->cgroup = __d_cgrp(file->f_dentry->d_parent);

		file->f_op = &cgroup_seqfile_operations;

		err = single_open(file, cgroup_seqfile_show, state);

		if (err < 0)

			kfree(state);

	} else if (cft->open)

		err = cft->open(inode, file);

	else

		err = 0;