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Subject[PATCH 3/5] cgroup add cftype->open/release() callbacks
Date
Pipe the newly added kernfs->open/release() callbacks through cftype.
While at it, as cleanup operations now can be performed from
->release() instead of ->seq_stop(), make the latter optional.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/cgroup-defs.h | 3 +++
kernel/cgroup.c | 24 +++++++++++++++++++++++-
2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 861b467..8a916dc 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -388,6 +388,9 @@ struct cftype {
struct list_head node; /* anchored at ss->cfts */
struct kernfs_ops *kf_ops;

+ int (*open)(struct kernfs_open_file *of);
+ void (*release)(struct kernfs_open_file *of);
+
/*
* read_u64() is a shortcut for the common case of returning a
* single integer. Use it in place of read()
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2ee9ec3..87167e4 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3503,6 +3503,23 @@ static int cgroup_events_show(struct seq_file *seq, void *v)
return 0;
}

+static int cgroup_file_open(struct kernfs_open_file *of)
+{
+ struct cftype *cft = of->kn->priv;
+
+ if (cft->open)
+ return cft->open(of);
+ return 0;
+}
+
+static void cgroup_file_release(struct kernfs_open_file *of)
+{
+ struct cftype *cft = of->kn->priv;
+
+ if (cft->release)
+ cft->release(of);
+}
+
static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off)
{
@@ -3553,7 +3570,8 @@ static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)

static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
{
- seq_cft(seq)->seq_stop(seq, v);
+ if (seq_cft(seq)->seq_stop)
+ seq_cft(seq)->seq_stop(seq, v);
}

static int cgroup_seqfile_show(struct seq_file *m, void *arg)
@@ -3575,12 +3593,16 @@ static int cgroup_seqfile_show(struct seq_file *m, void *arg)

static struct kernfs_ops cgroup_kf_single_ops = {
.atomic_write_len = PAGE_SIZE,
+ .open = cgroup_file_open,
+ .release = cgroup_file_release,
.write = cgroup_file_write,
.seq_show = cgroup_seqfile_show,
};

static struct kernfs_ops cgroup_kf_ops = {
.atomic_write_len = PAGE_SIZE,
+ .open = cgroup_file_open,
+ .release = cgroup_file_release,
.write = cgroup_file_write,
.seq_start = cgroup_seqfile_start,
.seq_next = cgroup_seqfile_next,
--
2.9.3
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