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Subject[RFC][PATCH 2/3] memcg:: seq_ops support for cgroup
Does anyone have a better idea ?
==

Currently, cgroup's seq_file interface just supports single_open.
This patch allows arbitrary seq_ops if passed.

For example, "status per cpu, status per node" can be very big
in general and they tend to use its own start/next/stop ops.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


---
include/linux/cgroup.h | 9 +++++++++
kernel/cgroup.c | 32 +++++++++++++++++++++++++++++---
2 files changed, 38 insertions(+), 3 deletions(-)
Index: mm-2.6.26-rc2-mm1/include/linux/cgroup.h
===================================================================
--- mm-2.6.26-rc2-mm1.orig/include/linux/cgroup.h
+++ mm-2.6.26-rc2-mm1/include/linux/cgroup.h
@@ -232,6 +232,11 @@ struct cftype {
*/
int (*read_seq_string) (struct cgroup *cont, struct cftype *cft,
struct seq_file *m);
+ /*
+ * If this is not NULL, read ops will use this instead of
+ * single_open(). Useful for showing very large data.
+ */
+ struct seq_operations *seq_ops;

ssize_t (*write) (struct cgroup *cgrp, struct cftype *cft,
struct file *file,
@@ -285,6 +290,10 @@ int cgroup_path(const struct cgroup *cgr

int cgroup_task_count(const struct cgroup *cgrp);

+
+struct cgroup *cgroup_of_seqfile(struct seq_file *m);
+struct cftype *cftype_of_seqfile(struct seq_file *m);
+
/* Return true if the cgroup is a descendant of the current cgroup */
int cgroup_is_descendant(const struct cgroup *cgrp);

Index: mm-2.6.26-rc2-mm1/kernel/cgroup.c
===================================================================
--- mm-2.6.26-rc2-mm1.orig/kernel/cgroup.c
+++ mm-2.6.26-rc2-mm1/kernel/cgroup.c
@@ -1540,6 +1540,16 @@ struct cgroup_seqfile_state {
struct cgroup *cgroup;
};

+struct cgroup *cgroup_of_seqfile(struct seq_file *m)
+{
+ return ((struct cgroup_seqfile_state *)m->private)->cgroup;
+}
+
+struct cftype *cftype_of_seqfile(struct seq_file *m)
+{
+ return ((struct cgroup_seqfile_state *)m->private)->cft;
+}
+
static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value)
{
struct seq_file *sf = cb->state;
@@ -1563,8 +1573,14 @@ static int cgroup_seqfile_show(struct se
static int cgroup_seqfile_release(struct inode *inode, struct file *file)
{
struct seq_file *seq = file->private_data;
+ struct cgroup_seqfile_state *state = seq->private;
+ struct cftype *cft = state->cft;
+
kfree(seq->private);
- return single_release(inode, file);
+ if (!cft->seq_ops)
+ return single_release(inode, file);
+ else
+ return seq_release(inode, file);
}

static struct file_operations cgroup_seqfile_operations = {
@@ -1585,7 +1601,7 @@ static int cgroup_file_open(struct inode
cft = __d_cft(file->f_dentry);
if (!cft)
return -ENODEV;
- if (cft->read_map || cft->read_seq_string) {
+ if (cft->read_map || cft->read_seq_string || cft->seq_ops) {
struct cgroup_seqfile_state *state =
kzalloc(sizeof(*state), GFP_USER);
if (!state)
@@ -1593,7 +1609,17 @@ static int cgroup_file_open(struct inode
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 (!cft->seq_ops)
+ err = single_open(file, cgroup_seqfile_show, state);
+ else {
+ err = seq_open(file, cft->seq_ops);
+ if (!err) {
+ struct seq_file *sf;
+ sf = ((struct seq_file *)file->private_data);
+ sf->private = state;
+ }
+ }
if (err < 0)
kfree(state);
} else if (cft->open)


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