[PATCH] xfs: fix in the setting of logbsize

[Ales Novak]

On 2015-6-8 15:04, Mark Tinguely wrote:

> On 06/07/15 04:16, Ales Novak wrote:
>> 
>> On 2015-6-6 00:22, Dave Chinner wrote:
>> 
>>> Can you give more information about the crashes? From this
>>> description, I do not know whether this is a work around or a fix
>>> because I don't know what code is actually causing the problem or
>>> the circumstances in which the crash occurs. Hence I cannot
>>> determine if your change is the right change to make or whether the
>>> documetnation is simply wrong and we have a real bug we shoul dbe
>>> fixing.
>> 
>> The crashes occurred with logsunit=192k and logbsize=256k. xlog_sync()
>> is calculating in logsunit units:
>> 
>> count = XLOG_LSUNITTOB(log, XLOG_BTOLSUNIT(log, count_init));
>> 
>> With count_init=256k, the calculated roundoff will try to cover that in
>> two 192k units. This roundoff is passed to the xlog_pack_data() which
>> walks the buffer and (hopefully) fails when it hits its 256k border.
>> 
>
> Talked about this once before:
>
> http://oss.sgi.com/archives/xfs/2013-03/msg00039.html
>
> Mark.
>

Thank you! I missed that.

Still I'd advocate for at least simple solution. Sure it's a root's fault 
if he tries to set logbsize not being integer multiple of logsunit, but 
crashing a kernel, that's bad...

-- 
Ales Novak