Re: [dm-devel] [BUG] pvmove corrupting XFS filesystems (was Re: [BUG] Internal error xfs_dir2_data_reada_verify)

Dave Chinner
2013-03-07T22:50:04Z

On Fri, Mar 08, 2013 at 09:31:40AM +1100, Dave Chinner wrote:
> On Thu, Mar 07, 2013 at 07:13:27AM -0500, Matteo Frigo wrote:
> > Matteo Frigo <athena@fftw.org> writes:
> >
> > > Well, I don't really know anything about this topic, so I may be
> > > completely off the mark, but dm-raid1.c:mirror_map() does indeed return
> > > EWOULDBLOCK, and EWOULDBLOCK is #define'd to be EAGAIN, so it seems to
> > > me that dm-raid1 does indeed return EAGAIN for "rw == READA" (which I
> > > assume is read-ahead) if the "region is not in-sync":
> > >
> > > /*
> > > * If region is not in-sync queue the bio.
> > > */
> > > if (!r || (r == -EWOULDBLOCK)) {
> > > if (rw == READA)
> > > return -EWOULDBLOCK;
> > >
> > > queue_bio(ms, bio, rw);
> > > return DM_MAPIO_SUBMITTED;
> > > }
> >
> > Dave (and others),
> >
> > do you have any suggestion on what should be done to fix this bug?
> >
> > I have tried returning -EIO instead of -EWOULDBLOCK, but xfs does not
> > like that. dm-zero.c:zero_map() appears to return -EIO too, so this is
> > another potential issue.
>
> You need the XFS patch I posted so that readahead buffer
> verification is avoided in the case of an error being returned from
> the readahead.

I don't recall if that patch was sent to this thread, so here it is:

http://oss.sgi.com/archives/xfs/2013-02/msg00516.html

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com