Re: a problem with dget

[Jan Hudec <bulb@ucw.cz>]

On Tue, Mar 25, 2003 at 06:47:00PM +0200, Nir Tzachar wrote:
> hello all.
> 
> i encountered a strange problem, involving the reference count of
> dentries.
> 
> first, let me describe my file system (i'll be brief.. ):
> im implementing a file system which is supposed to emulate an object
> storage device. i use a wrapper like file system (much like wrapfs,
> and actually based on it) to store files on an underlying f/s as objects.
> 
> i hope someone can help me, i've been tackling this problem for more than
> a week: when i create a file(say "tmp"), all is fine.
> the problem arises when i umount and then remount the file system.
> after im done with lookup (inode->i_op->lookup), dentry->d_count.counter
> ==1, as should be. but, when i enter the unlink function
> (inode->i_op->unlink ) its dentry->d_count.counter == 0 . why is that?
> nowhere in the vfs code does anyone decreases the counter b4
> inode->i_op->unlink is called . am i right?

Isn't that the little confusing semantics of lookup that's biting you?
When ->lookup returns non-NULL, real_lookup (the caller) puts the dentry
passed to ->lookup. So if you fill it in, you must return NULL and *NOT*
the dentry you recieved!

> the problem happens every time i try to do a dget an any dentry.

Yes, because you need to hold a reference to do dget.

-------------------------------------------------------------------------------
						 Jan 'Bulb' Hudec <bulb@ucw.cz>