Re-mounting removable btrfs on different device

Re-mounting removable btrfs on different device

[Remi Gauvin]

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I'm trying to use a BTRFS filesystem on a removable drive.

The first drive drive was added to the system, it was /dev/sdb

Files were added and device unmounted without error.

But when I re-attach the drive, it becomes /dev/sdg (kernel is fussy
about re-using /dev/sdb).

btrfs fi show: output:

Label: 'Archive 01'  uuid: 221222e7-70e7-4d67-9aca-42eb134e2041
	Total devices 1 FS bytes used 515.40GiB
	devid    1 size 931.51GiB used 522.02GiB path /dev/sdg1

This causes BTRFS to fail mounting the device with the following errors:

sd 3:0:0:0: [sdg] Attached SCSI disk
blk_partition_remap: fail for partition 1
BTRFS error (device sdb1): bdev /dev/sdg1 errs: wr 0, rd 1, flush 0,
corrupt 0, gen 0
blk_partition_remap: fail for partition 1
BTRFS error (device sdb1): bdev /dev/sdg1 errs: wr 0, rd 2, flush 0,
corrupt 0, gen 0
blk_partition_remap: fail for partition 1
BTRFS error (device sdb1): bdev /dev/sdg1 errs: wr 0, rd 3, flush 0,
corrupt 0, gen 0
blk_partition_remap: fail for partition 1
BTRFS error (device sdb1): bdev /dev/sdg1 errs: wr 0, rd 4, flush 0,
corrupt 0, gen 0
ata4: exception Emask 0x50 SAct 0x0 SErr 0x4090800 action 0xe frozen
ata4: irq_stat 0x00400040, connection status changed
ata4: SError: { HostInt PHYRdyChg 10B8B DevExch }


I've seen some patches on this list to add a btrfs device forget option,
which I presume would help with a situation like this.  Is there a way
to do that manually?

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Re: Re-mounting removable btrfs on different device

[Duncan]

Remi Gauvin posted on Thu, 06 Sep 2018 20:54:17 -0400 as excerpted:

> I'm trying to use a BTRFS filesystem on a removable drive.
> 
> The first drive drive was added to the system, it was /dev/sdb
> 
> Files were added and device unmounted without error.
> 
> But when I re-attach the drive, it becomes /dev/sdg (kernel is fussy
> about re-using /dev/sdb).
> 
> btrfs fi show: output:
> 
> Label: 'Archive 01'  uuid: 221222e7-70e7-4d67-9aca-42eb134e2041
> 	Total devices 1 FS bytes used 515.40GiB
> 	devid    1 size 931.51GiB used 522.02GiB path /dev/sdg1
> 
> This causes BTRFS to fail mounting the device [errors snipped]

> I've seen some patches on this list to add a btrfs device forget option,
> which I presume would help with a situation like this.  Is there a way
> to do that manually?

Without the mentioned patches, the only way (other than reboot) is to 
remove and reinsert the btrfs kernel module (assuming it's a module, not 
built-in), thus forcing it to forget state.

Of course if other critical mounted filesystems (such as root) are btrfs, 
or if btrfs is a kernel-built-in not a module and thus can't be removed, 
the above doesn't work and a reboot is necessary.  Thus the need for 
those patches you mentioned.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman

Re: Re-mounting removable btrfs on different device

[Remi Gauvin]

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On 2018-09-06 11:32 PM, Duncan wrote:

> Without the mentioned patches, the only way (other than reboot) is to 
> remove and reinsert the btrfs kernel module (assuming it's a module, not 
> built-in), thus forcing it to forget state.
> 
> Of course if other critical mounted filesystems (such as root) are btrfs, 
> or if btrfs is a kernel-built-in not a module and thus can't be removed, 
> the above doesn't work and a reboot is necessary.  Thus the need for 
> those patches you mentioned.
> 

Good to know, thanks.

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