Re: [RFC][PATCH] set_page_buffer_dirty should skip unmapped buffers

[Badari Pulavarty]

Jan Kara wrote:
>   Hi,
>
>   
> > Jan Kara wrote:
> >     
> > >  I've been looking more at the code and I have revived my patch fixing
> > > this part of the code. I've mildly tested the patch. Could you also give
> > > it a try? Thanks.
> > >
> > > 								Honza
> > >  
> > > ------------------------------------------------------------------------
> > >
> > > Original commit code assumes, that when a buffer on BJ_SyncData list is 
> > > locked,
> > > it is being written to disk. But this is not true and hence it can lead to 
> > > a
> > > potential data loss on crash. Also the code didn't count with the fact that
> > > journal_dirty_data() can steal buffers from committing transaction and 
> > > hence
> > > could write buffers that no longer belong to the committing transaction.
> > > Finally it could possibly happen that we tried writing out one buffer 
> > > several
> > > times.
> > >
> > > The patch below tries to solve these problems by a complete rewrite of the 
> > > data
> > > commit code. We go through buffers on t_sync_datalist, lock buffers needing
> > > write out and store them in an array. Buffers are also immediately refiled 
> > > to
> > > BJ_Locked list or unfiled (if the write out is completed). When the array 
> > > is
> > > full or we have to block on buffer lock, we submit all accumulated buffers 
> > > for
> > > IO.
> > >
> > > Signed-off-by: Jan Kara <jack@xxxxxxx>
> > >
> > >  
> > >       
> > I have been running 4+ hours with this patch and seems to work fine. I 
> > haven't hit any
> > assert yet :)
> >
> > I will let it run till tomorrow. I will let you know, how it goes.
> >     
>   Great, thanks. BTW: Do you have any performance tests handy? The
> changes are big enough to cause some unexpected performance regressions,
> livelocks... If you don't have anything ready, I can setup and run
> something myself.  Just that I don't like this testing too much ;).
>   
Tests are still running fine.

I don't have any performance tests handy. We have some automated tests I 
can schedule
to run to verify the stability aspects.

Thanks,
Badari

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