Hi,

I have a btrfs raid10 with 4 drives on Fedora 23 x64.
Currently, the array is mountable (non-degraded) and all the content
appears accessible without any errors -- except that "btrfs dev ready"
returns 1 and "btrfs fi show -d" says "*** Some devices missing".

Originally:

1 of the drives failed (/dev/sdb; command timeouts, link reset
messages), causing a kernel panic by btrfs getting really confused.
After reboot, I got "parent transid verify failed" while trying to mount.

Booted into USB stick (fedora 23 lxde live), found /dev/sdb2 by SMART
errors, saw that I can mount degraded (without /dev/sdb2) without any
errors.
Replaced the bad drive with a new one, ran "btrfs dev add", "btrfs del
missing" using btrfs-progs v4.2.2 -- this returned an error saying no
"missing" device or something.
Upgraded to btrfs-progs 4.3.1, this time it went fine.
Reboot to main system got stuck on systemd waiting for btrfs device.

After some back and forth, I found that "ready" returns an error and "fi
show" is inconsistent.
/dev/sda2 was showing up as dev id 5 (2 missing)

Tried removing /dev/sdb2 again and "btrfs replace"ing the now-missing
/dev/sdb2 with the fresh instance of /dev/sdb2.
Now /dev/sdb2 shows up as device 6 (2 and 5 not listed).
"fi show" on mounted /dev/sda2 looks normal; on unmounted /dev/sda2
shows "Total devices 5" and "Some devices missing"


# uname -a
Linux slon 4.2.3-300.fc23.x86_64 #1 SMP Mon Oct 5 15:42:54 UTC 2015
x86_64 x86_64 x86_64 GNU/Linux

# btrfs fi df /mnt
Data, RAID10: total=1.29TiB, used=1.29TiB
System, RAID10: total=64.00MiB, used=160.00KiB
Metadata, RAID10: total=4.00GiB, used=3.12GiB
GlobalReserve, single: total=512.00MiB, used=0.00B