How to deal with with backing device dropping out

[Nathan Dehnel <ncdehnel@xxxxxxxxx>]

I have a btrfs raid10 array, and occasionally a drive will disconnect
temporarily. After it reconnects though, it is no longer listed by
lsblk with a /dev/bcache* device under it, and it usually has a
different /dev/sd* drive letter as well, and "btrfs fi show"
subsequently reports the device as missing.

I have tried "echo  /dev/sd* > /sys/fs/bcache/register" but it does
not make the /dev/bcache* device reappear (not while the filesystem is
mounted, at least).

Is there any way to deal with this, short of rebooting?

NAME          MAJ:MIN  RM   SIZE RO TYPE  MOUNTPOINT
sdb             8:16    0 931.5G  0 disk
└─sdb1          8:17    0 931.5G  0 part
  └─bcache0   251:0     0 931.5G  0 disk  /
sdc             8:32    0 931.5G  0 disk
└─sdc1          8:33    0 931.5G  0 part
  └─bcache1   251:128   0 931.5G  0 disk
sdd             8:48    0 931.5G  0 disk
└─sdd1          8:49    0 931.5G  0 part
  └─bcache2   251:256   0 931.5G  0 disk
sde             8:64    0 931.5G  0 disk
└─sde1          8:65    0 931.5G  0 part
  └─bcache3   251:384   0 931.5G  0 disk
sdf             8:80    0 931.5G  0 disk
└─sdf1          8:81    0 931.5G  0 part
  └─bcache4   251:512   0 931.5G  0 disk
sdg             8:96    0 931.5G  0 disk
└─sdg1          8:97    0 931.5G  0 part
  └─bcache5   251:640   0 931.5G  0 disk
sdh             8:112   0 931.5G  0 disk
└─sdh1          8:113   0 931.5G  0 part
  └─bcache6   251:768   0 931.5G  0 disk
sdi             8:128   0 931.5G  0 disk
└─sdi1          8:129   0 931.5G  0 part
  └─bcache7   251:896   0 931.5G  0 disk
sdj             8:144   0 931.5G  0 disk
└─sdj1          8:145   0 931.5G  0 part
  └─bcache8   251:1024  0 931.5G  0 disk
sdk             8:160   0 931.5G  0 disk
└─sdk1          8:161   0 931.5G  0 part
  └─bcache9   251:1152  0 931.5G  0 disk
nvme0n1       259:0     0  13.4G  0 disk
├─nvme0n1p1   259:1     0     2M  0 part
├─nvme0n1p2   259:2     0   128M  0 part
└─nvme0n1p3   259:3     0  13.3G  0 part
  └─md0         9:0     0  13.3G  0 raid1
    ├─bcache0 251:0     0 931.5G  0 disk
    ├─bcache1 251:128   0 931.5G  0 disk
    ├─bcache2 251:256   0 931.5G  0 disk
    ├─bcache3 251:384   0 931.5G  0 disk
    ├─bcache4 251:512   0 931.5G  0 disk
    ├─bcache5 251:640   0 931.5G  0 disk
    ├─bcache6 251:768   0 931.5G  0 disk
    ├─bcache7 251:896   0 931.5G  0 disk
    ├─bcache8 251:1024  0 931.5G  0 disk
    └─bcache9 251:1152  0 931.5G  0 disk
nvme1n1       259:4     0  13.4G  0 disk
├─nvme1n1p1   259:5     0     2M  0 part
├─nvme1n1p2   259:6     0   128M  0 part
└─nvme1n1p3   259:7     0  13.3G  0 part
  └─md0         9:0     0  13.3G  0 raid1
    ├─bcache0 251:0     0 931.5G  0 disk
    ├─bcache1 251:128   0 931.5G  0 disk
    ├─bcache2 251:256   0 931.5G  0 disk
    ├─bcache3 251:384   0 931.5G  0 disk
    ├─bcache4 251:512   0 931.5G  0 disk
    ├─bcache5 251:640   0 931.5G  0 disk
    ├─bcache6 251:768   0 931.5G  0 disk
    ├─bcache7 251:896   0 931.5G  0 disk
    ├─bcache8 251:1024  0 931.5G  0 disk
    └─bcache9 251:1152  0 931.5G  0 disk

NAME          MAJ:MIN  RM   SIZE RO TYPE  MOUNTPOINT
sdb             8:16    0 931.5G  0 disk
└─sdb1          8:17    0 931.5G  0 part
  └─bcache0   251:0     0 931.5G  0 disk  /
sdc             8:32    0 931.5G  0 disk
└─sdc1          8:33    0 931.5G  0 part
  └─bcache1   251:128   0 931.5G  0 disk
sdd             8:48    0 931.5G  0 disk
└─sdd1          8:49    0 931.5G  0 part
  └─bcache2   251:256   0 931.5G  0 disk
sde             8:64    0 931.5G  0 disk
└─sde1          8:65    0 931.5G  0 part
  └─bcache3   251:384   0 931.5G  0 disk
sdf             8:80    0 931.5G  0 disk
└─sdf1          8:81    0 931.5G  0 part
  └─bcache4   251:512   0 931.5G  0 disk
sdg             8:96    0 931.5G  0 disk
└─sdg1          8:97    0 931.5G  0 part
  └─bcache5   251:640   0 931.5G  0 disk
sdh             8:112   0 931.5G  0 disk
└─sdh1          8:113   0 931.5G  0 part
  └─bcache6   251:768   0 931.5G  0 disk
sdi             8:128   0 931.5G  0 disk
└─sdi1          8:129   0 931.5G  0 part
  └─bcache7   251:896   0 931.5G  0 disk
sdj             8:144   0 931.5G  0 disk
└─sdj1          8:145   0 931.5G  0 part
  └─bcache8   251:1024  0 931.5G  0 disk
sdk             8:160   0 931.5G  0 disk
└─sdk1          8:161   0 931.5G  0 part
nvme0n1       259:0     0  13.4G  0 disk
├─nvme0n1p1   259:1     0     2M  0 part
├─nvme0n1p2   259:2     0   128M  0 part
└─nvme0n1p3   259:3     0  13.3G  0 part
  └─md0         9:0     0  13.3G  0 raid1
    ├─bcache0 251:0     0 931.5G  0 disk
    ├─bcache1 251:128   0 931.5G  0 disk
    ├─bcache2 251:256   0 931.5G  0 disk
    ├─bcache3 251:384   0 931.5G  0 disk
    ├─bcache4 251:512   0 931.5G  0 disk
    ├─bcache5 251:640   0 931.5G  0 disk
    ├─bcache6 251:768   0 931.5G  0 disk
    ├─bcache7 251:896   0 931.5G  0 disk
    └─bcache8 251:1024  0 931.5G  0 disk
nvme1n1       259:4     0  13.4G  0 disk
├─nvme1n1p1   259:5     0     2M  0 part
├─nvme1n1p2   259:6     0   128M  0 part
└─nvme1n1p3   259:7     0  13.3G  0 part
  └─md0         9:0     0  13.3G  0 raid1
    ├─bcache0 251:0     0 931.5G  0 disk
    ├─bcache1 251:128   0 931.5G  0 disk
    ├─bcache2 251:256   0 931.5G  0 disk
    ├─bcache3 251:384   0 931.5G  0 disk
    ├─bcache4 251:512   0 931.5G  0 disk
    ├─bcache5 251:640   0 931.5G  0 disk
    ├─bcache6 251:768   0 931.5G  0 disk
    ├─bcache7 251:896   0 931.5G  0 disk
    └─bcache8 251:1024  0 931.5G  0 disk