Re: [PATCH v6 00/10] proc: modernize proc to support multiple private instances

 	hidepid=	Set /proc/<pid>/ access mode.
 	gid=		Set the group authorized to learn processes information.
+	pidonly=	Show only task related subset of procfs.

+static int proc_dir_open(struct inode *inode, struct file *file)
+{
+	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
+
+	if (proc_fs_pidonly(fs_info) == PROC_PIDONLY_ON)
+		return -ENOENT;
+
+	return 0;
+}
+
 /*
  * These are the generic /proc directory operations. They
  * use the in-memory "struct proc_dir_entry" tree to parse

@@ -338,6 +357,7 @@ static const struct file_operations proc_dir_operations = {
 	.llseek			= generic_file_llseek,
 	.read			= generic_read_dir,
 	.iterate_shared		= proc_readdir,
+	.open			= proc_dir_open,

 static int proc_reg_open(struct inode *inode, struct file *file)
 {
+	struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
 	struct proc_dir_entry *pde = PDE(inode);
 	int rv = 0;
 	typeof_member(struct file_operations, open) open;
 	typeof_member(struct file_operations, release) release;
 	struct pde_opener *pdeo;
 
+	if (proc_fs_pidonly(fs_info) == PROC_PIDONLY_ON)
+		return -ENOENT;

--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
+/* definitions for hide_pid field */
+enum {
+	HIDEPID_OFF	  = 0,
+	HIDEPID_NO_ACCESS = 1,
+	HIDEPID_INVISIBLE = 2,
+	HIDEPID_NOT_PTRACABLE = 3, /* Limit pids to only ptracable pids */
+};