linux-kernel - Re: [PATCH 2.6.24-rc4] proc: Remove/Fix proc generic d

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Date:	Mon, 10 Dec 2007 22:35:14 +0100
From:	vandrove@...cvut.cz
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Denis V. Lunev" <den@...ru>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>, rjw@...k.pl,
	trond.myklebust@....uio.no, gnome42@...il.com,
	linux-kernel@...r.kernel.org, bfields@...ldses.org, den@...nvz.org,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [PATCH 2.6.24-rc4] proc: Remove/Fix proc generic d_revalidate

Quoting Andrew Morton <akpm@...ux-foundation.org>:

> On Mon, 10 Dec 2007 16:32:18 +0300 "Denis V. Lunev" <den@...ru> wrote:
> >
> 
> Plese don't top-post.  It makes replying to you rather awkward.
> 
> > could you, plz, check patch sent by Eric above in this thread.
> > 
> > I have tried it on my test node and it works for module you have
> > provided. The problem exists without it.
> > 
> 
> When Peter says "with your patch in place" I assume that he's referring to
> Eric's latest patch, namely.

Sorry, I was not clear.  No, I meant Eric's original patch.  Without
d_revalidate() problem does not occur.
                                                   Petr

> 
> --- a/fs/proc/generic.c~proc-remove-fix-proc-generic-d_revalidate
> +++ a/fs/proc/generic.c
> @@ -374,16 +374,9 @@ static int proc_delete_dentry(struct den
>  	return 1;
>  }
>  
> -static int proc_revalidate_dentry(struct dentry *dentry, struct nameidata
> *nd)
> -{
> -	d_drop(dentry);
> -	return 0;
> -}
> -
>  static struct dentry_operations proc_dentry_operations =
>  {
>  	.d_delete	= proc_delete_dentry,
> -	.d_revalidate	= proc_revalidate_dentry,
>  };
>  
>  /*
> 
> So we still have problems, it appears.
> 
> > 
> > Petr Vandrovec wrote:
> > > Eric W. Biederman wrote:
> > >> Ultimately to implement /proc perfectly we need an implementation
> > >> of d_revalidate because files and directories can be removed behind
> > >> the back of the VFS, and d_revalidate is the only way we can let
> > >> the VFS know that this has happened.
> > >>
> > >> So until we get a proper test for keeping dentries in the dcache
> > >> fix the current d_revalidate method by completely removing it.  This
> > >> returns us to the current status quo.
> > > 
> > > Hello,
> > >    I know that I'm late to the party, but mount points is not only
> > > problem with d_revalidate.  With your patch in place module below gets
> > > refcount incremented by two every time I do 'ls -la /proc/fs/vmblock'.
> > > 
> > >
> > > #include <linux/kernel.h>
> > > #include <linux/module.h>
> > > #include <linux/proc_fs.h>
> > > 
> > > static int vmblockinit(void) {
> > >    struct proc_dir_entry *controlProcDirEntry;
> > > 
> > >    /* Create /proc/fs/vmblock */
> > >    controlProcDirEntry = proc_mkdir("vmblock", proc_root_fs);
> > >    if (!controlProcDirEntry) {
> > >       printk(KERN_DEBUG "Bad...\n");
> > >       return -EINVAL;
> > >    }
> > >    controlProcDirEntry->owner = THIS_MODULE;
> > >    return 0;
> > > }
> > > 
> > > static void vmblockexit(void) {
> > >    remove_proc_entry("vmblock", proc_root_fs);
> > > }
> > > 
> > > module_init(vmblockinit);
> > > module_exit(vmblockexit);
> > > 
> > > 
> > > (code comes from VMware's vmblock module,
> > > http://sourceforge.net/project/showfiles.php?group_id=204462)
> > >                         Thanks,
> > >                             Petr
> > > 
> > > 
> 
> 
> 



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