Re: 2.6.12-rc2 + rc3: reaim with ext3 - system stalls.

[Jan Kara]

  Hello,

> Started seeing some odd behaviour with recent kernels, haven't been able to
> run it down, could use some suggestions/help.
> 
> Running re-aim7 with 2.6.12-rc2 and rc3, if I use xfs, jfs, or
> reiserfs things work just fine.
> 
> With ext3, the  test stalls, such that:
> CPU is 50% idle, 50% waiting IO (top)
> vmstat shows one process blocked wio
  I've looked through your dumps and I spotted where is the problem -
it's our well known and beloved lock inversion between PageLock and
transaction start (giving CC to Badari who's the author of the patch
that introduced it AFAIK).
  The correct order is: first get PageLock and *then* start transaction.
But in ext3_writeback_writepages() first ext3_journal_start() is called
and then __mpage_writepages is called that tries to do LockPage and
deadlock is there. Badari, could you please fix that (sadly I think that
would not be easy)? Maybe we should back out those changes until it gets
fixed...

								Honza

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