Re: [Qemu-devel] [PATCH] block: init bs->io_base correctly to avoid locking

[Peter Lieven]

Am 10.01.2013 um 11:19 schrieb Paolo Bonzini <address@hidden>:

> Il 10/01/2013 10:21, Peter Lieven ha scritto:
>> If io_limits are specified during runtime that exceed the number of
>> operations in flight
>> bs->io_base is not initialized in the else statement in
>> bdrv_exceed_io_limits().
>> The wait time calculated in bdrv_exceed_{bps,iops}_limits is thus
>> totally wrong
>> and the machine locks.
>> 
>> Signed-off-by: Peter Lieven <address@hidden>
>> ---
>> block.c |    4 ++++
>> 1 file changed, 4 insertions(+)
>> 
>> diff --git a/block.c b/block.c
>> index 4e28c55..309aa85 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -159,6 +159,10 @@ void bdrv_io_limits_enable(BlockDriverState *bs)
>>     bs->slice_start = qemu_get_clock_ns(vm_clock);
>>     bs->slice_end   = bs->slice_start + bs->slice_time;
>>     memset(&bs->io_base, 0, sizeof(bs->io_base));
> 
> Please remove this memset.
> 
>> +    bs->io_base.bytes[0] = bs->nr_bytes[0];
>> +    bs->io_base.bytes[1] = bs->nr_bytes[1];
>> +    bs->io_base.ios[0] = bs->nr_ops[0];
>> +    bs->io_base.ios[1] = bs->nr_ops[1];
>>     bs->io_limits_enabled = true;
>> }
>> 
> 
> Also, perhaps you can just call
> 
>    bdrv_exceed_io_limits(bs, 0, 0, NULL);

won`t this segfault if only one of bps or ions limit is set?
in this case it reads wait before returning false in
bdrv_exceed_{bps,iops}_limits().


> 
> (which also subsumes the setting of slice_time, slice_start, slice_end).
> 
> Paolo