Re: [PATCH 1/5] jbd: strictly check for write errors on data buffers

Andreas Dilger
2008-06-05T18:49:59Z

On Jun 05, 2008 09:20 -0700, Andrew Morton wrote:
> On Thu, 5 Jun 2008 10:29:48 -0400 Theodore Tso <tytso@mit.edu> wrote:
> > On Thu, Jun 05, 2008 at 08:33:27PM +0900, Hidehiro Kawai wrote:
> > >
> > > My patch doesn't change the policy. JBD aborts the journal when
> > > it detects I/O error in file data since 2.6.11. Perhaps this patch:
> > > http://marc.info/?l=linux-kernel&m=110483888632225
> > > I just added missing error checkings.
> >
> > Looking at the code paths touched by patch you referenced, you are
> > correct. And Andrew even signed off on it. :-)
> >
> > But if someone was only examining the patch, it wasn't obvious that
> > the journal was getting aborted when the JBD layer was forcing buffers
> > from t_sync_datalist to disk. So I suspect the change went in without
> > proper consideration of the net effect. You just called it out
> > explicitly in the subject line, which caused Andrew to ask some good
> > questions; questions that weren't asked in 2005.
>
> Sigh. An object lesson in the value of good changelogging :(

... and the value of "diff -p" so it is clear what function is being changed.

> I guess we need to undo this. And yes, propagating errors into AS_EIO
> is the way. I guess that's safe without holding lock_page(), as long
> as the bh is pinned.

Something like the following instead if -EIO and journal abort:

if (!buffer_uptodate(bh)) {
set_bit(AS_EIO, &bh->b_page->mapping->flags);
SetPageError(bh->b_page);
}

It seems end_buffer_async_write() does this already, but
journal_do_submit_data() uses end_buffer_write_sync() and it does not
do either of those operations.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.