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List:       linux-btrfs
Subject:    Re: Re-mounting removable btrfs on different device
From:       Duncan <1i5t5.duncan () cox ! net>
Date:       2018-09-07 3:32:30
Message-ID: pan$d71b0$8d25ba8$5bb37179$bc1641a5 () cox ! net
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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

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