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

Jan Kara
2006-09-07T20:47:56Z

Hi,

> > Ugh! Are you sure? For this path the buffer must be attached (only) to
> > the running transaction. But then how the commit code comes to it?
> > Somebody would have to even manage to refile the buffer from the
> > committing transaction to the running one while the buffer is in wbuf[].
> > Could you check whether someone does __journal_refile_buffer() on your
> > marked buffers, please? Or whether we move buffer to BJ_Locked list in
> > the write_out_data: loop? Thanks.
> >
> >
>
> I added more debug in __journal_refile_buffer() to see if the marked
> buffers are getting refiled. I am able to reproduce the problem,
> but I don't see any debug including my original prints. (It looks as
> if none of my debug code exists) - its really confusing.
>
> I will keep looking and get back to you.
>
> I may try Andrew's buffer debug patch - if I get desperate.
Ho, hum, I think I see what is hapenning. I think we steal the buffer
from commit in journal_dirty_data() (called e.g. from ext3_writepage()).
There we also take care of writing out the buffer so it's mostly OK.
Except that the commit code still keeps the reference to the buffer in
wbuf[]. So the right solution along the lines of your one would be to
check that each buffer in wbuf[] is buffer_jbd(), belongs to the right
transaction and list and only in that case run submit_bh() on it...

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