Re: [Xen-devel] [PATCH] xen-blkfront: check feature-persitent on resume

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

On 23/05/14 19:51, Konrad Rzeszutek Wilk wrote:
> On Thu, May 22, 2014 at 04:40:07PM +0200, Roger Pau Monne wrote:
>> We are missing a check to see if the backend supports persistent
>> grants on resume, meaning we will always run with the value fetched
>> from the firsts host on which we run on.
>>
>> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>> Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
>> ---
>>  drivers/block/xen-blkfront.c |   23 ++++++++++++++++-------
>>  1 files changed, 16 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
>> index efe1b47..00ae36b 100644
>> --- a/drivers/block/xen-blkfront.c
>> +++ b/drivers/block/xen-blkfront.c
>> @@ -1430,6 +1430,20 @@ static void split_bio_end(struct bio *bio, int error)
>>      bio_put(bio);
>>  }
>>  
>> +static void blkfront_setup_persistent(struct blkfront_info *info)
>> +{
>> +    unsigned int persistent;
>> +    int err;
>> +
>> +    err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
>> +                        "feature-persistent", "%u", &persistent,
>> +                        NULL);
>> +    if (err)
>> +            info->feature_persistent = 0;
>> +    else
>> +            info->feature_persistent = persistent;
>> +}
>> +
>>  static int blkif_recover(struct blkfront_info *info)
>>  {
>>      int i;
>> @@ -1456,6 +1470,7 @@ static int blkif_recover(struct blkfront_info *info)
>>      info->shadow_free = info->ring.req_prod_pvt;
>>      info->shadow[BLK_RING_SIZE-1].req.u.rw.id = 0x0fffffff;
>>  
>> +    blkfront_setup_persistent(info);
>>      rc = blkfront_setup_indirect(info);
>>      if (rc) {
>>              kfree(copy);
>> @@ -1851,13 +1866,7 @@ static void blkfront_connect(struct blkfront_info 
>> *info)
>>      if (!err && discard)
>>              blkfront_setup_discard(info);
>>  
>> -    err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
>> -                        "feature-persistent", "%u", &persistent,
>> -                        NULL);
>> -    if (err)
>> -            info->feature_persistent = 0;
>> -    else
>> -            info->feature_persistent = persistent;
>> +    blkfront_setup_persistent(info);
> 
> Should we also flush the ones that are on the info->grants list if
> we turning it off?

This path is only taken on the first connection, further calls to
blkfront_connect from resume code don't get here, because they take the
BLKIF_STATE_SUSPENDED path and just call blkif_recover and return. And
on disconnection blkfront_connect doesn't even get called.

Roger.


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