Re: [PATCH v2 3/3] btrfs-progs: device: add remove missing-all

[Duncan <1i5t5.duncan@cox.net>]

Misono, Tomohiro posted on Mon, 16 Oct 2017 13:35:08 +0900 as excerpted:

> On 2017/10/16 12:30, Anand Jain wrote:
>> 
>> 
>> On 10/13/2017 01:27 PM, Duncan wrote:
>>> Misono, Tomohiro posted on Wed, 11 Oct 2017 11:18:50 +0900 as
>>> excerpted:
>>>
>>>> Add 'btrfs remove missing-all' to remove all the missing devices at
>>>> once for improving usability.
>>>>
>>>> Example:
>>>>   sudo mkfs.btrfs -f -d raid1 /dev/sdb1 /dev/sdb2 /dev/sdb3 /dev/sdb4
>>>>   sudo wipefs -a /dev/sdb1 /dev/sdb3 sudo mount -o degraded /dev/sdb2
>>>>   /mnt <--
>> 
>> 
>>    I agree with Duncan here. This step itself will fail even with RO
>>    option. Do you have any patch that is not in the ML which will make
>>    this step a success in the first place ?
>> 
>> Thanks, Anand
>> 
>> 
> commit 21634a19f646 ("btrfs: Introduce a function to check if all chunks
> a OK for degraded rw mount") allow this from 4.14 (I checked on
> 4.14-rc4).

That's why I said recent patches allow it in corner-cases.  However, I 
think those corner-cases would I think be difficult to document concisely 
in the manpage, and without that, I believe the option would be more 
confusing than helpful, since people would expect it to actually work 
when it won't, for them.

> But I will withdraw this patch as Duncan suggests.

If someone comes up with a satisfactory way to explain at a manpage level 
the corner-cases in which removing more than one missing device at a time 
can work...

-- 
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"Every nonfree program has a lord, a master --
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