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Re: [dm-devel] [BUG] pvmove corrupting XFS filesystems (was Re: [BUG] In

To: Matteo Frigo <athena@xxxxxxxx>
Subject: Re: [dm-devel] [BUG] pvmove corrupting XFS filesystems (was Re: [BUG] Internal error xfs_dir2_data_reada_verify)
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 27 Feb 2013 13:29:28 +1100
Cc: dm-devel@xxxxxxxxxx, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <87y5eah4xz.fsf@xxxxxxxx>
References: <87d2vnc34r.fsf@xxxxxxxx> <20130226044039.GM5551@dastard> <20130227010414.GD1514@xxxxxxxxxxxxxxxxxx> <20130227014900.GY5551@dastard> <87y5eah4xz.fsf@xxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, Feb 26, 2013 at 09:21:44PM -0500, Matteo Frigo wrote:
> Dave Chinner <david@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx

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