I had a raid 5 array of 3 disks using btrfs (raid provided by btrfs) one of the disks was damaged and I replaced the disk via:btrfs device add /dev/sdc /media/raid/ btrfs device delete missing /media/raid/ which forced a rebalance accross the disks, after which the FS was fine.One reboot later:[11152.188020] BTRFS info (device sdb): enabling auto defrag [11152.188028] BTRFS info (device sdb): disk space caching is enabled [11152.189762] BTRFS: failed to read chunk tree on sdb [11152.196224] BTRFS: open_ctree failed pc ~ # mount -a mount: wrong fs type, bad option, bad superblock on /dev/sde, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so. The OS started by commenting out that line in fstab, I've uncommented that line afterwards.LABEL=raid /media/raid btrfs compress=lzo,noatime,autodefragI'm using Gentoo Linux, kernel 4.0.5.Here's btrfs fi show:Label: 'raid'  uuid: 906ed4e3-52c5-4eb7-bd06-4810c0b84902Total devices 3 FS bytes used 775.29GiBdevid    1 size 931.51GiB used 390.06GiB path /dev/sdbdevid    3 size 931.51GiB used 390.04GiB path /dev/sdedevid    4 size 931.51GiB used 390.03GiB path /dev/sdcpc / # btrfs-find-root /dev/sdcSuperblock thinks the generation is 1758Superblock thinks the level is 0Found tree root at 30818304 gen 1758 level 0Well block 30457856(gen: 1757 level: 0) seems good, but generation/level doesn't match, want gen: 1758 level: 0Well block 29753344(gen: 1590 level: 0) seems good, but generation/level doesn't match, want gen: 1758 level: 0Well block 29507584(gen: 1589 level: 0) seems good, but generation/level doesn't match, want gen: 1758 level: 0Well block 4243456(gen: 3 level: 0) seems good, but generation/level doesn't match, want gen: 1758 level: 0Well block 4194304(gen: 2 level: 0) seems good, but generation/level doesn't match, want gen: 1758 level: 0
I'm unable to mount a btrfs partition
btrfs