Re: [PATCH] Btrfs: fix wrong failed mirror_num of read-repair on raid56

[Liu Bo <bo.li.liu@oracle.com>]

On Mon, Mar 27, 2017 at 07:07:15PM +0200, David Sterba wrote:
> On Fri, Mar 24, 2017 at 12:13:42PM -0700, Liu Bo wrote:
> > In raid56 senario, after trying parity recovery, we didn't set
> > mirror_num for btrfs_bio with failed mirror_num, hence
> > end_bio_extent_readpage() will report a random mirror_num in dmesg
> > log.
> > 
> > Cc: David Sterba <dsterba@suse.cz>
> > Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
> > ---
> >  fs/btrfs/volumes.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> > index 73d56ee..be64e4a 100644
> > --- a/fs/btrfs/volumes.c
> > +++ b/fs/btrfs/volumes.c
> > @@ -6197,6 +6197,7 @@ int btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
> >  		} else {
> >  			ret = raid56_parity_recover(fs_info, bio, bbio,
> >  						    map_length, mirror_num, 1);
> > +			btrfs_io_bio(bio)->mirror_num = mirror_num;
> 
> Should the mirror be set inside raid56_parity_recover? There's another
> caller, scrub_submit_raid56_bio_wait, that does not update the
> bio->mirror_num. I am not sure if this is the same case though.
>

scrub_submit_raid56_bio_wait doesn't need to, but yes, we could set the
mirror inside raid56_parity_recover iff @generic_io is 1.

Thanks,

-liubo

> >  		}
> >  
> >  		btrfs_bio_counter_dec(fs_info);