[PATCH 1/4] proc: Implement proc_single_file_operations

[ebiederm@xmission.com (Eric W. Biederman)]

Currently many /proc/pid files use a crufty precursor to
the current seq_file api, and they don't have direct access
to the pid_namespace or the pid of for which they are displaying
data.

So implement proc_single_file_operations to make the seq_file
routines easy to use, and to give access to the full state of the
pid of we are displaying data for.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
 fs/proc/base.c          |   43 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/proc_fs.h |    3 +++
 2 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a17c268..e9ff77e 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -125,6 +125,10 @@ struct pid_entry {
 	NOD(NAME, (S_IFREG|(MODE)), 			\
 		NULL, &proc_info_file_operations,	\
 		{ .proc_read = &proc_##OTYPE } )
+#define ONE(NAME, MODE, OTYPE)				\
+	NOD(NAME, (S_IFREG|(MODE)), 			\
+		NULL, &proc_single_file_operations,	\
+		{ .proc_show = &proc_##OTYPE } )
 
 int maps_protect;
 EXPORT_SYMBOL(maps_protect);
@@ -571,6 +575,45 @@ static const struct file_operations proc_info_file_operations = {
 	.read		= proc_info_read,
 };
 
+static int proc_single_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct pid_namespace *ns;
+	struct pid *pid;
+	struct task_struct *task;
+	int ret;
+
+	ns = inode->i_sb->s_fs_info;
+	pid = proc_pid(inode);
+	task = get_pid_task(pid, PIDTYPE_PID);
+	if (!task)
+		return -ESRCH;
+
+	ret = PROC_I(inode)->op.proc_show(m, ns, pid, task);
+
+	put_task_struct(task);
+	return ret;
+}
+
+static int proc_single_open(struct inode *inode, struct file *filp)
+{
+	int ret;
+	ret = single_open(filp, proc_single_show, NULL);
+	if (!ret) {
+		struct seq_file *m = filp->private_data;
+
+		m->private = inode;
+	}
+	return ret;
+}
+
+static const struct file_operations proc_single_file_operations = {
+	.open		= proc_single_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 static int mem_open(struct inode* inode, struct file* file)
 {
 	file->private_data = (void*)((long)current->self_exec_id);
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 1273c6e..69307c9 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -257,6 +257,9 @@ extern void kclist_add(struct kcore_list *, void *, size_t);
 union proc_op {
 	int (*proc_get_link)(struct inode *, struct dentry **, struct vfsmount **);
 	int (*proc_read)(struct task_struct *task, char *page);
+	int (*proc_show)(struct seq_file *m,
+		struct pid_namespace *ns, struct pid *pid,
+		struct task_struct *task);
 };
 
 struct proc_inode {
-- 
1.5.3.rc6.17.g1911