Re: [PATCH v2] dma-debug: enhance dma_debug_device_change() to checkfor mapping errors

[Shuah Khan]

On 12/30/2013 07:15 AM, Joerg Roedel wrote:
> 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@xxxxxxxxxxx>
> > ---
> >   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.

I did explore separate function option and backed off from it since the 
new routine will have to duplicate what device_dma_allocations() does 
except that it checks for entry->map_err_type.

I still have the patch that does that saved away. If you still prefer 
that approach, I can rework the patch and send it.

-- Shuah


--
Shuah Khan
Senior Linux Kernel Developer - Open Source Group
Samsung Research America(Silicon Valley)
shuah.kh@xxxxxxxxxxx | (970) 672-0658
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