[1805985.267438] BTRFS info (device dm-6): allowing degraded mounts [1805985.267566] BTRFS info (device dm-6): disk space caching is enabled [1805985.267676] BTRFS info (device dm-6): has skinny extents [1805987.187857] BTRFS warning (device dm-6): missing devices (1) exceeds the limit (0), writeable mount is not allowed [1805987.228990] BTRFS error (device dm-6): open_ctree failed [chris@f25s ~]$ sudo mount -o noatime,degraded,ro /dev/mapper/sdb /mnt [chris@f25s ~]$ sudo btrfs fi df /mnt Data, RAID1: total=434.00GiB, used=432.46GiB Data, single: total=1.00GiB, used=1.66MiB System, RAID1: total=8.00MiB, used=48.00KiB System, single: total=32.00MiB, used=32.00KiB Metadata, RAID1: total=2.00GiB, used=729.17MiB Metadata, single: total=1.00GiB, used=0.00B GlobalReserve, single: total=495.02MiB, used=0.00B [chris@f25s ~]$
So the sequence is: 1. mkfs.btrfs -d raid1 -m raid1 <devs 2x) 2. fill it with a bunch of data over a few months, always mounted normally with default options 3. physically remove 1 of 2 devices, and do a degraded mount. This mounts without error, and more stuff is added. Volume is umounted. 4. Try to mount the same 1 of 2 devices, with degraded mount option, and I get the first error, "writeable mount is not allowed". 5. Try to mount the same 1 of 2 devices, with degraded,ro option, and it mounts, and then I captured the 'btfs fi df' above. So very clearly there are single chunks added during the degraded rw mount. But does 1.66MiB of data in that single data chunk make sense? And does 0.00 MiB of metadata in that single metadata chunk make sense? I'm not sure, seems unlikely. Most of what happened in that subvolume since the previous snapshot was moving things around, reorganizing, not adding files. So, maybe 1.66MiB data added is possible? But definitely the metadata changes must be in the raid1 chunks, while the newly created single profile metadata chunk is left unused. So I think there's more than one bug going on here, separate problems for data and metadata. Chris Murphy -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
