linux-kernel - Re: A question about proc file system

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Message-ID: <20121128120855.53181bb2@pyramind.ukuu.org.uk>
Date:	Wed, 28 Nov 2012 12:08:55 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Yangbin (Robin)" <robin.yb@...wei.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fs@...r.kernel.org" <linux-fs@...r.kernel.org>
Subject: Re: A question about proc file system

On Wed, 28 Nov 2012 02:55:30 +0000
"Yangbin (Robin)" <robin.yb@...wei.com> wrote:

> Hi all:
> 
> 	I write a kernel module which make a dir and create a file in proc file system. 
> I use proc_mkdir() and create_proc_entry() in init and use remove_proc_entry() in exit.
> Now I got a problem during my test:
> 1. open terminal A, insmod and cd into the dir the module created in proc
> 2. open terminal B. rmmod and insmod angain.
> Then I cannot see the file which should be created by the module, unless terminal A quit the dir.
> 
> This will be ok with regale file system like ext3, one teminal's operation will not affert others.
> Is this a bug or not?

It's not. You are doing the same as this


	mkdir /tmp/example
	cd /tmp/example
	rmdir /tmp/example

	mkdir /tmp/example

in Unix like systems the file handles and current directory references
apply to the object itself not to the path.

When yo reload the driver you create a new and different directory that
has the same name but is not the same thing.

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