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Date: Tue, 01 Jul 2003 12:55:04 +0200
From: Peter Enderborg <pme@hyglo.com>
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To: linux-kernel@vger.kernel.org
CC: "Theodore Ts'o" <tytso@mit.edu>, Linus Torvalds <torvalds@osdl.org>
Subject: Procfs open hook bug.
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I have done this little patch for the procfs_example.c

diff procfs_example.c 
kernels/linux-2.4.20/Documentation/DocBook/procfs_example.c
87,91d86
< static int open_qp(struct inode * inode, struct file * file)
< {
<   printk("Open my node %p %p \n",inode,file);
<   return -EINVAL;
< }
180c175
<       foo_file->proc_fops->open=open_qp;
---
 >

And when loading this module. The procfs gets broken. I get EINVAL for 
open on
/proc/meminfo and all other procfs info. Why? Should procfs inodes don't 
have full
filesematics? And it don't help to unload the module.

Strange. And a look in generic.c in fs/proc/

static struct file_operations proc_file_operations = {
    llseek:        proc_file_lseek,
    read:        proc_file_read,
    write:        proc_file_write,
};

Is this saying that we can not have the other fops on procfs inodes? No 
ioctl,open ?