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

[Dave Chinner]

On Tue, Feb 26, 2013 at 09:21:44PM -0500, Matteo Frigo wrote:
> Dave Chinner <david at fromorbit.com> writes:
> 
> > On Wed, Feb 27, 2013 at 01:04:14AM +0000, Alasdair G Kergon wrote:
> >> (Quick pointers that might be relevant)
> >> 
> >> EAGAIN, I'm not aware of dm itself returning that on the i/o path.
> >
> > Neither am I, but it's coming from somewhere in the IO path...
> 
> 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;
> 	}

Trees, forest....

Thanks for pointing out the obvious, Matteo. :)

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com