linux-kernel - Re: [PATCH v2] xen/blkfront: fix ring info addressing

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Date:   Thu, 5 Mar 2020 14:40:00 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     Roger Pau Monné <roger.pau@...rix.com>
Cc:     xen-devel@...ts.xenproject.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH v2] xen/blkfront: fix ring info addressing

On 05.03.20 13:42, Roger Pau Monné wrote:
> On Thu, Mar 05, 2020 at 12:40:44PM +0100, Juergen Gross wrote:
>> Commit 0265d6e8ddb890 ("xen/blkfront: limit allocated memory size to
>> actual use case") made struct blkfront_ring_info size dynamic. This is
>> fine when running with only one queue, but with multiple queues the
>> addressing of the single queues has to be adapted as the structs are
>> allocated in an array.
>>
>> Fixes: 0265d6e8ddb890 ("xen/blkfront: limit allocated memory size to actual use case")
>> Reported-by: Sander Eikelenboom <linux@...elenboom.it>
>> Signed-off-by: Juergen Gross <jgross@...e.com>
>> ---
>> V2:
>> - get rid of rinfo_ptr() helper
>> - use proper parenthesis in for_each_rinfo()
>> - rename rinfo parameter of for_each_rinfo()
>> ---
>>   drivers/block/xen-blkfront.c | 79 +++++++++++++++++++++++---------------------
>>   1 file changed, 42 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
>> index e2ad6bba2281..8e844da826db 100644
>> --- a/drivers/block/xen-blkfront.c
>> +++ b/drivers/block/xen-blkfront.c
>> @@ -213,6 +213,7 @@ struct blkfront_info
>>   	struct blk_mq_tag_set tag_set;
>>   	struct blkfront_ring_info *rinfo;
>>   	unsigned int nr_rings;
>> +	unsigned int rinfo_size;
>>   	/* Save uncomplete reqs and bios for migration. */
>>   	struct list_head requests;
>>   	struct bio_list bio_list;
>> @@ -259,6 +260,18 @@ static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo);
>>   static void blkfront_gather_backend_features(struct blkfront_info *info);
>>   static int negotiate_mq(struct blkfront_info *info);
>>   
>> +#define for_each_rinfo(info, ptr, idx)				\
>> +	for ((ptr) = (info)->rinfo, (idx) = 0;			\
>> +	     (idx) < (info)->nr_rings;				\
>> +	     (idx)++, (ptr) = (void *)(ptr) + (info)->rinfo_size)
>> +
>> +static struct blkfront_ring_info *get_rinfo(struct blkfront_info *info,
> 
> I still think inline should be added here, but I don't have such a
> strong opinion to block the patch on it.

I can add it if you like that better. Won't make much difference in the
end.

> Also, info should be constified AFAICT.

Yes.

> 
> With at least info constified:
> 
> Acked-by: Roger Pau Monné <roger.pau@...rix.com>
> 
> Can you queue this through the Xen tree?

Sure.


Juergen