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cgroup: introduce struct cgroup_pidlist_open_file

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For pidlist files, seq_file->private pointed to the loaded
cgroup_pidlist; however, pidlist loading is planned to be moved to
cgroup_pidlist_start() for kernfs conversion and seq_file->private
needs to carry more information from open to allow that.

This patch introduces struct cgroup_pidlist_open_file which contains
type, cgrp and pidlist and updates pidlist seq_file->private to point
to it using seq_open_private() and seq_release_private().  Note that
this eventually will be replaced by kernfs_open_file.

While this patch makes more information available to seq_file
operations, they don't use it yet and this patch doesn't introduce any
behavior changes except for allocation of the extra private struct.

v2: use __seq_open_private() instead of seq_open_private() for brevity
    as suggested by Li.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-11-29 10:42:58 -05:00
parent b1a2136731
commit 62236858f3
1 changed files with 27 additions and 12 deletions
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39
kernel/cgroup.c
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@ -3468,6 +3468,13 @@ struct cgroup_pidlist {
struct delayed_work destroy_dwork;
};
/* seq_file->private points to the following */
struct cgroup_pidlist_open_file {
enum cgroup_filetype type;
struct cgroup *cgrp;
struct cgroup_pidlist *pidlist;
};
/*
* 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.
@ -3739,7 +3746,8 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
* after a seek to the start). Use a binary-search to find the
* next pid to display, if any
*/
struct cgroup_pidlist *l = s->private;
struct cgroup_pidlist_open_file *of = s->private;
struct cgroup_pidlist *l = of->pidlist;
int index = 0, pid = *pos;
int *iter;
@ -3769,13 +3777,15 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
static void cgroup_pidlist_stop(struct seq_file *s, void *v)
{
struct cgroup_pidlist *l = s->private;
up_read(&l->rwsem);
struct cgroup_pidlist_open_file *of = s->private;
up_read(&of->pidlist->rwsem);
}
static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
{
struct cgroup_pidlist *l = s->private;
struct cgroup_pidlist_open_file *of = s->private;
struct cgroup_pidlist *l = of->pidlist;
pid_t *p = v;
pid_t *end = l->list + l->length;
/*
@ -3820,11 +3830,11 @@ static void cgroup_release_pid_array(struct cgroup_pidlist *l)
static int cgroup_pidlist_release(struct inode *inode, struct file *file)
{
struct cgroup_pidlist *l;
struct cgroup_pidlist_open_file *of;
l = ((struct seq_file *)file->private_data)->private;
cgroup_release_pid_array(l);
return seq_release(inode, file);
of = ((struct seq_file *)file->private_data)->private;
cgroup_release_pid_array(of->pidlist);
return seq_release_private(inode, file);
}
static const struct file_operations cgroup_pidlist_operations = {
@ -3843,6 +3853,7 @@ static const struct file_operations cgroup_pidlist_operations = {
static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
{
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
struct cgroup_pidlist_open_file *of;
struct cgroup_pidlist *l;
int retval;
@ -3853,12 +3864,16 @@ static int cgroup_pidlist_open(struct file *file, enum cgroup_filetype type)
/* configure file information */
file->f_op = &cgroup_pidlist_operations;
retval = seq_open(file, &cgroup_pidlist_seq_operations);
if (retval) {
of = __seq_open_private(file, &cgroup_pidlist_seq_operations,
sizeof(*of));
if (!of) {
cgroup_release_pid_array(l);
return retval;
return -ENOMEM;
}
((struct seq_file *)file->private_data)->private = l;
of->type = type;
of->cgrp = cgrp;
of->pidlist = l;
return 0;
}
static int cgroup_tasks_open(struct inode *unused, struct file *file)