Re: [Xen-devel] [PATCH RESEND] xen/blkfront: improve protection against issuing unsupported REQ_FUA

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> writes:

> On 12/01/2014 08:01 AM, Vitaly Kuznetsov wrote:
>> Guard against issuing unsupported REQ_FUA and REQ_FLUSH was introduced
>> in d11e61583 and was factored out into blkif_request_flush_valid() in
>> 0f1ca65ee. However:
>> 1) This check in incomplete. In case we negotiated to feature_flush = 
>> REQ_FLUSH
>>     and flush_op = BLKIF_OP_FLUSH_DISKCACHE (so FUA is unsupported) FUA 
>> request
>>     will still pass the check.
>> 2) blkif_request_flush_valid() is misnamed. It is bool but returns true when
>>     the request is invalid.
>> 3) When blkif_request_flush_valid() fails -EIO is being returned. It seems 
>> that
>>     -EOPNOTSUPP is more appropriate here.
>> Fix all of the above issues.
>>
>> This patch is based on the original patch by Laszlo Ersek and a comment by
>> Jeff Moyer.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> Reviewed-by: Laszlo Ersek <lersek@xxxxxxxxxx>
>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
>
> (although, as I mentioned last time, a companion patch to remove
> flush_op would be a good thing to have)
>

Thanks, it is on my todo list but I'm trying to separate this
(potential) bugfix from straight cleanup.

> -boris
>
>> ---
>>   drivers/block/xen-blkfront.c | 14 ++++++++------
>>   1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
>> index 5ac312f..2e6c103 100644
>> --- a/drivers/block/xen-blkfront.c
>> +++ b/drivers/block/xen-blkfront.c
>> @@ -582,12 +582,14 @@ static inline void flush_requests(struct blkfront_info 
>> *info)
>>              notify_remote_via_irq(info->irq);
>>   }
>>   -static inline bool blkif_request_flush_valid(struct request *req,
>> -                                         struct blkfront_info *info)
>> +static inline bool blkif_request_flush_invalid(struct request *req,
>> +                                           struct blkfront_info *info)
>>   {
>>      return ((req->cmd_type != REQ_TYPE_FS) ||
>> -            ((req->cmd_flags & (REQ_FLUSH | REQ_FUA)) &&
>> -            !info->flush_op));
>> +            ((req->cmd_flags & REQ_FLUSH) &&
>> +             !(info->feature_flush & REQ_FLUSH)) ||
>> +            ((req->cmd_flags & REQ_FUA) &&
>> +             !(info->feature_flush & REQ_FUA)));
>>   }
>>     /*
>> @@ -612,8 +614,8 @@ static void do_blkif_request(struct request_queue *rq)
>>              blk_start_request(req);
>>   -          if (blkif_request_flush_valid(req, info)) {
>> -                    __blk_end_request_all(req, -EIO);
>> +            if (blkif_request_flush_invalid(req, info)) {
>> +                    __blk_end_request_all(req, -EOPNOTSUPP);
>>                      continue;
>>              }
>>   

-- 
  Vitaly

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