From mboxrd@z Thu Jan  1 00:00:00 1970
From: Shaya Potter <spotter@cs.columbia.edu>
Subject: Re: file struct's dentry being null?
Date: 02 Jul 2003 12:32:29 -0400
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Cc: Nikita Danilov <Nikita@Namesys.COM>, linux-fsdevel@vger.kernel.org
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To: Eli Carter <eli.carter@inet.com>
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List-Id: linux-fsdevel.vger.kernel.org

On Wed, 2003-07-02 at 12:18, Eli Carter wrote:
> Shaya Potter wrote:
> > On Wed, 2003-07-02 at 11:58, Nikita Danilov wrote:
> > 
> >>Shaya Potter writes:
> >> > I decided to do an experiment, in fput, I did a 
> >> > 
> >> > struct file * next;
> >> > next = (struct file *) file->f_list.next;
> >>
> >>->f_list.next points to the ->f_list member of next struct file rather
> >>than to the struct file itself. This is how it works for all struct
> >>list_head embedded into objects.
> > 
> > 
> > yes, I understand that, the idea being that it's the first entry in the
> > struct that you want to link list, so can get the next struct by just
> > dereferencing the list_head (as &list_head == &struct)
> 
> No, his point was that &list_head != $struct, but rather &struct == 
> &list_head - some_offset.
> 
> So the code you'd need would look like:
> struct file *next;
> next = list_entry( <address of the list_head>, file, f_list );

ok, even with that fix, I'm still getting the same sort of output

I'm printing out 6 different distinct memory locations whose next entry
in the file list has a null dentry.

The system operates normally like this, so just trying to figure out
what its dereferencing.

this is the block of code I stick in fput()

{
	struct file * next;
	next = list_entry(file->f_list.next, struct file, f_list);
	if ( !next->f_dentry )
	{
		printk("deleting dentry whose next is null!, next = %d\n",next);
	}

}