Re: BTRFS raid6 unmountable after a couple of days of usage.

[Ryan Bourne <hub@spotprint.com.au>]

On 14/07/15 11:25 PM, Austin S Hemmelgarn wrote:
> On 2015-07-14 07:49, Austin S Hemmelgarn wrote:
>> So, after experiencing this same issue multiple times (on almost a
>> dozen different kernel versions since 4.0) and ruling out the
>> possibility of it being caused by my hardware (or at least, the RAM,
>> SATA controller and disk drives themselves), I've decided to report it
>> here.
>>
>> The general symptom is that raid6 profile filesystems that I have are
>> working fine for multiple weeks, until I either reboot or otherwise
>> try to remount them, at which point the system refuses to mount them.

>>
> Further updates, I just tried mounting the filesystem from the image
> above again, this time passing device= options for each device in the
> FS, and it seems to be working fine now.  I've tried this with the other
> filesystems however, and they still won't mount.
>

I have experienced a similar problem on a raid1 with kernels from 3.17
onward following a kernel panic.

I have found that passing the other device as the main device to mount
will often work.
E.g.

# mount -o device=/dev/sdb,device=/dev/sdc /dev/sdb /mountpoint
open_ctree failed

# mount -o device=/dev/sdb,device=/dev/sdc /dev/sdc /mountpoint
mounts correctly.

If I then do an immediate umount and try again I get the same thing, but
after some time using the filesystem, I can umount and either device is
working for the mount again.