Re: Slow jffs2 startup on DOM

[Michael Michael <memmel2@yahoo.com>]

Hack attack ...
Okay to test I added a call to  blockmtd_sync right at
the end of block_mtd  write
here's the monster diff
*** blkmtd.c	Thu Feb 21 05:28:39 2002
--- blkmtd.c.mike	Thu Feb 21 05:28:19 2002
***************
*** 843,852 ****
--- 843,853 ----
        SetPageUptodate(pages[pagecnt]);
        flush_dcache_page(pages[pagecnt]);
        page_cache_release(pages[pagecnt]);
      }
      kfree(pages);
+ 		blkmtd_sync(mtd);
      return 0;
    }

This fixed everything for me so I guess I was right.
But I really  this driver needs to be cleaned out to
just write direct try it with and without this change.

Mike



--- Michael Michael <memmel2@yahoo.com> wrote:
> Umm I'm thinking about this a bit more
> 
> the problem is I think in 
> linux/drivers/mtd/devices/blkmtd.c
> 
> I think that it is using the buffered device through
> the io buf. Thus even when you unmount you havent
> flushed the io buf of the underlying block device.
> Its my understanding the the linux block devices are
> not raw but read and right through the io buf.
> 
> in blkmtd.c blkmtd_readpage and  write_queue_task it
> does a
>  brw_kiovec which is in buffer.c at this point I'm
> getting a bit lost but it looks like the io is
> definatly buffered  with the writes occurring
> through
> a io buffer in a thread. The point is there not
> "direct"
> and not garunteed to occur until write_queue_task
> runs.
> 
> 
> I think blkmtd needs to use the new raw device api
> not
> the linux block devices i.e...
> 
> block_dev_directIO in fs/block_dev.c umm Nope dangit
> that calls evenutually brw_kiovec.  So its got to be
> the write thread which should be synchronous on
> writes
> ???
> I'm pretty sure thats the root of the problem a
> quick
> look showed the other mtd device writing directly so
> this is the "big difference" why is this in a thread
> ?
> 
> 
> I'm sure the Gad Hayisraeli is right about
> umount/sync
> working the question is why. 
> Answer  blkmtd writes in a thread and umount/sync
> wakes it up correctly. I don't think it should do
> that.
> 
> Did I win a star : )
> 
> --- David Woodhouse <dwmw2@infradead.org> wrote:
> > 
> > memmel2@yahoo.com said:
> > > I think in this case its caused by the
> underlying
> > block device
> > > cleaning things up. Not JFFS2. I think he's
> right.
> > 
> > 
> > I didn't think the DOM knew anything about when it
> > was opened/closed by the 
> > operating system, so it didn't get a chance to
> > behave differently on an 
> > unmount? It's just an IDE drive, isn't it?
> > 
> > --
> > dwmw2
> > 
> > 
> 
> 
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