Re: [Xen-devel] [PATCH 3.13-rc1] xen-blkfront: Silence pfn maybe-uninitialized warning

[Roger Pau Monnà <roger.pau@xxxxxxxxxx>]

On 14/11/13 23:24, Konrad Rzeszutek Wilk wrote:
> Tim Gardner <tim.gardner@xxxxxxxxxxxxx> wrote:
>> pfn cannot actually be used unless (!info->feature_persistent), nor is
>> pfn accessed in get_grant() unless (!info->feature_persistent), but
>> silence
>> this warning anyway. gcc-4.8
>>
>> drivers/block/xen-blkfront.c: In function 'do_blkif_request':
>> drivers/block/xen-blkfront.c:508:20: warning: 'pfn' may be used
>> uninitialized in this function [-Wmaybe-uninitialized]
>>     gnt_list_entry = get_grant(&gref_head, pfn, info);
>>                    ^
>> drivers/block/xen-blkfront.c:492:19: note: 'pfn' was declared here
>>     unsigned long pfn;
>>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
>> Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
>> Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>

Acked-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>

>> ---
>> drivers/block/xen-blkfront.c |    2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/block/xen-blkfront.c
>> b/drivers/block/xen-blkfront.c
>> index 432db1b..5f926de 100644
>> --- a/drivers/block/xen-blkfront.c
>> +++ b/drivers/block/xen-blkfront.c
>> @@ -489,7 +489,7 @@ static int blkif_queue_request(struct request *req)
>>
>>                      if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
>>                          (i % SEGS_PER_INDIRECT_FRAME == 0)) {
>> -                            unsigned long pfn;
>> +                            unsigned long uninitialized_var(pfn);
>>
>>                              if (segments)
>>                                      kunmap_atomic(segments);
> 
> I have a similar patch from Roger that sets pfn=0. 
> 
> Roger could you repost your patch please or if you feel that this patch makes 
> sense then comment on it?

I'm fine with this patch, although I'm more used to the classic pfn = 0.


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