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Date: Tue, 1 Apr 2008 11:35:04 -0500
From: Nathan Lynch <ntl@pobox.com>
To: Jens Osterkamp <jens@de.ibm.com>
Subject: Re: [PATCH] RTAS - adapt procfs interface
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	Paul Mackerras <paulus@samba.org>, cbe-oss-dev@ozlabs.org
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Jens Osterkamp wrote:
> 
> Handling of the proc_dir_entry->count has being changed in 2.6.24-rc5.

Do you know which commit caused the change?


> After this change the default value for pde->count is 1 and not 0 as it
> was in earlier kernels. Therefore, if we want to check wether our procfs
> file is already opened (already in use), we have to check if pde->count
> is not greater than 2 but not 1.
> 
> Signed-off-by: Maxim Shchetynin <maxim@de.ibm.com>
> Signed-off-by: Jens Osterkamp <jens@de.ibm.com>
> 
> Index: linux-2.6/arch/powerpc/kernel/rtas_flash.c
> ===================================================================
> --- linux-2.6.orig/arch/powerpc/kernel/rtas_flash.c
> +++ linux-2.6/arch/powerpc/kernel/rtas_flash.c
> @@ -356,7 +356,7 @@ static int rtas_excl_open(struct inode *
>  
>  	/* Enforce exclusive open with use count of PDE */
>  	spin_lock(&flash_file_open_lock);
> -	if (atomic_read(&dp->count) > 1) {
> +	if (atomic_read(&dp->count) > 2) {
>  		spin_unlock(&flash_file_open_lock);
>  		return -EBUSY;
>  	}

One could argue that the real problem is using the proc_dir_entry's
reference count to enforce exclusive open.