linux-kernel - Re: [PATCH v2] dma-debug: enhance dma_debug_device

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Message-ID: <20131230141511.GC2799@8bytes.org>
Date:	Mon, 30 Dec 2013 15:15:12 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Shuah Khan <shuah.kh@...sung.com>
Cc:	akpm@...ux-foundation.org, alexander.h.duyck@...el.com,
	linux-kernel@...r.kernel.org, shuahkhan@...il.com
Subject: Re: [PATCH v2] dma-debug: enhance dma_debug_device_change() to check
 for mapping errors

On Wed, Nov 13, 2013 at 01:56:08PM -0700, Shuah Khan wrote:
> dma-debug checks to verify if driver validated the address returned by
> dma mapping routines when driver does unmap. If a driver doesn't call
> unmap, failure to check mapping errors isn't detected and reported.
> 
> Enhancing existing bus notifier_call dma_debug_device_change() to check
> for mapping errors at the same time it detects leaked dma buffers for
> BUS_NOTIFY_UNBOUND_DRIVER event. It scans for mapping errors and if any
> found, prints one warning message that includes mapping error count.
> 
> Signed-off-by: Shuah Khan <shuah.kh@...sung.com>
> ---
>  lib/dma-debug.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
> index d87a17a..e34865e 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -717,6 +717,7 @@ static int device_dma_allocations(struct device *dev, struct dma_debug_entry **o
>  	struct dma_debug_entry *entry;
>  	unsigned long flags;
>  	int count = 0, i;
> +	int map_err_cnt = 0;
>  
>  	local_irq_save(flags);
>  
> @@ -724,6 +725,8 @@ static int device_dma_allocations(struct device *dev, struct dma_debug_entry **o
>  		spin_lock(&dma_entry_hash[i].lock);
>  		list_for_each_entry(entry, &dma_entry_hash[i].list, list) {
>  			if (entry->dev == dev) {
> +				if (entry->map_err_type == MAP_ERR_NOT_CHECKED)
> +					map_err_cnt += 1;
>  				count += 1;
>  				*out_entry = entry;

I think it is better to check for this in a seperate function and use
err_printk instead of dev_warn in the end to print the errors.
The new function can then be called in the dma_debug_device_change
callback like device_dma_allocations is.


	Joerg


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