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

Jan Kara
2006-09-08T08:25:32Z

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@suse.cz>
> >
> >
> 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 ;).

Honza

--
Jan Kara <jack@suse.cz>
SuSE CR Labs