Hi Marc,
On 26/3/20 4:14 AM, Marc MERLIN wrote:
Thanks for the suggestion Nikolay
Dear Anand, David,
I see that
https://gitlab.freedesktop.org/seanpaul/dpu-staging/commit/228a73abde5c04428678e917b271f8526cfd90ed
may have helped, but is this really something a user should know/do?
Why does a device that disappeared from the bus, need to be manually
unregistered?
Are users really supposed to know this?
Why does btrfs device scan not invalidate the cache of devices and keep
remembering a device that's gone (not visible in new scan)?
btrfs device scan --forget is only useful to cleanup the unmounted
devices, per the logs below the device was mounted when it disappeared.
More below.
Thanks,
Marc
On Sat, Mar 21, 2020 at 11:25:04PM +0200, Nikolay Borisov wrote:
On 21.03.20 г. 22:23 ч., Marc MERLIN wrote:
/dev/sde blipped off the bus (hardware issue?) and came
back as /dev/sdq.
Except btrfs won't let me scan or mount it.
I was able to btrfs check it though and that came back clean.
gargamel:~# ls -l /dev/sde
ls: cannot access '/dev/sde': No such file or directory
gargamel:~# mount /dev/sdq1 /mnt/mnt
mount: /mnt/mnt: mount(2) system call failed: File exists.
gargamel:~# dmesg |tail -1
[2560371.195249] BTRFS warning (device sde1): duplicate device fsid:devid for 727c7ba3-f6f9-462a-8472-453dd7d46d8a:1 old:/dev/sde1 new:/dev/sdq1
This indicates the device was mounted when it disappeared. So it
re-appears with the new path, but as its fsid+uuid+devid matches
with the old still mounted device we rightly consider it as an
alien device and fail the mount.
To avoid assigning new path to the reappearing device we need to
close/pause the device path when it disappears. I need to figure
out if there is any KPI from the block layer to help doing that.
Anyone- any idea if there is anything in the block layer which can
do the callback into the filesystem if the device disappears?
Thanks, Anand
gargamel:~# btrfs device scan
Scanning for Btrfs filesystems
ERROR: device scan failed on '/dev/sdq1': File exists
ERROR: there are 1 errors while registering devices
gargamel:~# dmesg |tail -1
[2560416.434529] BTRFS warning (device sde1): duplicate device fsid:devid for 727c7ba3-f6f9-462a-8472-453dd7d46d8a:1 old:/dev/sde1 new:/dev/sdq1
gargamel:~# grep sde /proc/mounts
cgroup2 /sys/fs/cgroup/unified cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate 0 0
gargamel:~#
gargamel:~# lsblk -f |grep 727c7ba3-f6f9-462a-8472-453dd7d46d8a
└─sdq1 btrfs btrfs_space 727c7ba3-f6f9-462a-8472-453dd7d46d8a
gargamel:~#
So, that FS isn't a duplicate anymore and I see to have no way out except reboot
which I'll do now.
Was there another way around it? Obviously this is not desirable
behaviour, in the past, I was able to remount the device when it came
back.
Presumably you could have used the device forget functionality that got
introduced in 5.1, i.e the BTRFS_IOC_FORGET_DEV ioctl. For more info
check out: 228a73abde5c04428678e917b271f8526cfd90ed
Thanks,
Marc
