Re: [PATCH 0/4] Btrfs: RAID 5/6 missing device replace

[Omar Sandoval <osandov@osandov.com>]

On Mon, May 11, 2015 at 12:58:11AM -0700, Omar Sandoval wrote:
> A user reported on Bugzilla that they were seeing kernel BUGs when
> attempting to replace a missing device on a RAID 6 array. After
> identifying the apparent cause of the BUG, I reached the conclusion that
> there wasn't a quick fix. Maybe Miao Xie can point something out that I
> missed, as he originally implemented device replace on RAID 5/6 :)
> 
> Patch 4 has the details, but the main problem is that we can't create
> bios for a missing device, so the main scrub code path isn't very
> useful. On RAID 5/6, since we only have one mirror for any piece of
> data, the missing device is the only mirror we can use. Clearly, (unless
> I missed something), this case needs to be handled differently.
> 
> These patches are on top of v4.1-rc2. I ran the scrub and replace
> xfstests and the script below, which also reproduces the original BUG.
> 
> Thanks!
> 
> Omar Sandoval (4):
>   Btrfs: remove misleading handling of missing device scrub
>   Btrfs: count devices correctly in readahead during RAID 5/6 replace
>   Btrfs: add RAID 5/6 BTRFS_RBIO_REBUILD_MISSING operation
>   Btrfs: fix device replace of a missing RAID 5/6 device
> 
>  fs/btrfs/raid56.c |  87 +++++++++++++++++++++++++----
>  fs/btrfs/raid56.h |  10 +++-
>  fs/btrfs/reada.c  |   4 +-
>  fs/btrfs/scrub.c  | 164 +++++++++++++++++++++++++++++++++++++++++++++---------
>  4 files changed, 225 insertions(+), 40 deletions(-)
> 

Ping for review.

-- 
Omar