On 2019/06/13 23:09, Josef Bacik wrote: > On Fri, Jun 07, 2019 at 10:10:14PM +0900, Naohiro Aota wrote: >> If the btrfs volume has mirrored block groups, it unconditionally makes >> un-mirrored block groups read only. When we have mirrored block groups, but >> don't have writable block groups, this will drop all writable block groups. >> So, check if we have at least one writable mirrored block group before >> setting un-mirrored block groups read only. >> > > I don't understand why you want this. Thanks, > > Josef > This is necessary to handle e.g. btrfs/124 case. When we mount degraded RAID1 FS and write to it, and then re-mount with full device, the write pointers of corresponding zones of written BG differ. The patch 07 mark such block group as "wp_broken" and make it read only. In this situation, we only have read only RAID1 BGs because of "wp_broken" and un-mirrored BGs are also marked read only, because we have RAID1 BGs. As a result, all the BGs are now read only, so that we cannot even start the rebalance to fix the situation.
