ceph-volume: filter out non-existing devices

[1] has broken teuthology tests.

```
[root@smithi097 /]# ls -l /sys/block/
total 0
lrwxrwxrwx 1 root root 0 Jul 25 14:15 dm-0 -> ../devices/virtual/block/dm-0
lrwxrwxrwx 1 root root 0 Jul 25 14:15 dm-1 -> ../devices/virtual/block/dm-1
lrwxrwxrwx 1 root root 0 Jul 25 14:15 dm-2 -> ../devices/virtual/block/dm-2
lrwxrwxrwx 1 root root 0 Jul 25 14:15 dm-3 -> ../devices/virtual/block/dm-3
lrwxrwxrwx 1 root root 0 Jul 25 14:15 dm-4 -> ../devices/virtual/block/dm-4
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop0 -> ../devices/virtual/block/loop0
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop1 -> ../devices/virtual/block/loop1
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop2 -> ../devices/virtual/block/loop2
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop3 -> ../devices/virtual/block/loop3
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop4 -> ../devices/virtual/block/loop4
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop5 -> ../devices/virtual/block/loop5
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop6 -> ../devices/virtual/block/loop6
lrwxrwxrwx 1 root root 0 Jul 25 14:13 loop7 -> ../devices/virtual/block/loop7
lrwxrwxrwx 1 root root 0 Jul 25 14:12 nvme0n1 -> ../devices/pci0000:00/0000:00:02.0/0000:02:00.0/nvme/nvme0/nvme0n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme1c1n1 -> ../devices/virtual/nvme-fabrics/ctl/nvme1/nvme1c1n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme1n1 -> ../devices/virtual/nvme-subsystem/nvme-subsys1/nvme1n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme2c2n1 -> ../devices/virtual/nvme-fabrics/ctl/nvme2/nvme2c2n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme2n1 -> ../devices/virtual/nvme-subsystem/nvme-subsys2/nvme2n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme3c3n1 -> ../devices/virtual/nvme-fabrics/ctl/nvme3/nvme3c3n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme3n1 -> ../devices/virtual/nvme-subsystem/nvme-subsys3/nvme3n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme4c4n1 -> ../devices/virtual/nvme-fabrics/ctl/nvme4/nvme4c4n1
lrwxrwxrwx 1 root root 0 Jul 25 14:18 nvme4n1 -> ../devices/virtual/nvme-subsystem/nvme-subsys4/nvme4n1
lrwxrwxrwx 1 root root 0 Jul 25 14:12 sda -> ../devices/pci0000:00/0000:00:1f.2/ata5/host4/target4:0:0/4:0:0:0/block/sda
[root@smithi097 /]#
```

devices like `nvme1c1n1` exist in `/sys/block` but aren't present in `/dev`

```
[root@smithi097 /]# ls -l /dev/nvme*
crw------- 1 root root  10, 122 Jul 25 14:16 /dev/nvme-fabrics
crw------- 1 root root 240,   0 Jul 25 14:12 /dev/nvme0
brw-rw---- 1 root disk 259,   0 Jul 25 14:15 /dev/nvme0n1
crw------- 1 root root 240,   1 Jul 25 14:16 /dev/nvme1
brw-rw---- 1 root disk 259,   2 Jul 25 15:24 /dev/nvme1n1
crw------- 1 root root 240,   2 Jul 25 14:16 /dev/nvme2
brw-rw---- 1 root disk 259,   4 Jul 25 15:24 /dev/nvme2n1
crw------- 1 root root 240,   3 Jul 25 14:16 /dev/nvme3
brw-rw---- 1 root disk 259,   6 Jul 25 15:24 /dev/nvme3n1
crw------- 1 root root 240,   4 Jul 25 14:16 /dev/nvme4
brw-rw---- 1 root disk 259,   8 Jul 25 15:24 /dev/nvme4n1
[root@smithi097 /]#
```

If a device isn't actually present in `/dev`, `get_block_devs_sysfs()` shouldn't return it.

[1] https://github.com/ceph/ceph/commit/c7f017b21ade3762ba5b7b9688bed72c6b6

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>
(cherry picked from commit 0ee8351e4d564724aa68a2b8d03bc53e281e7fc9)

diff --git a/src/ceph-volume/ceph_volume/util/disk.py b/src/ceph-volume/ceph_volume/util/disk.py
index cc59e5dfc65291d3a5a1d9bbb3b3b76b7a225fad..26df9dba56d4f78174680f93e35c26f034cefdf0 100644 (file)
--- a/src/ceph-volume/ceph_volume/util/disk.py
+++ b/src/ceph-volume/ceph_volume/util/disk.py
@@ -781,6 +781,8 @@ def get_block_devs_sysfs(_sys_block_path='/sys/block', _sys_dev_block_path='/sys
     dev_names = os.listdir(_sys_block_path)
     for dev in dev_names:
         name = kname = os.path.join("/dev", dev)
+        if not os.path.exists(name):
+            continue
         type_ = 'disk'
         holders = os.listdir(os.path.join(_sys_block_path, dev, 'holders'))
         if get_file_contents(os.path.join(_sys_block_path, dev, 'removable')) == "1":