[PATCH] xfs: fix in the setting of logbsize

[Ales Novak]

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.

-- 
Ales Novak