Re: btrfs-image gets stuck, using 100%, looping on bad file descriptor

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2015-08-18 22:55, Timothy Normand Miller wrote:
> On Tue, Aug 18, 2015 at 10:48 PM, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>>
>>
>> Timothy Normand Miller wrote on 2015/08/18 22:46 -0400:
>>>
>>> On Tue, Aug 18, 2015 at 9:32 PM, Qu Wenruo <quwenruo@cn.fujitsu.com>
>>> wrote:
>>>>
>>>> Hi Timothy,
>>>>
>>>> Although I have replied to the bugzilla, IMHO it's more appropriate to
>>>> discuss it in mail list, as it's not a kernel bug.
>>>>
>>>
>>> All four devices were online.  The "missing" one was a drive that
>>> died, which was replaced by a new one, but btrfs wouldn't finish the
>>> deletion of the missing device.
>>>
>> By replaced, did you mean "btrfs replace"? Or just change the physical disk
>> without using "btrfs replace"?
>
> Here's what happened:
>
> - A drive started throwing bad sectors.  Somehow this caused metadata
> on other drives to get messed up.
> - I took that drive offline and mounted degraded (it's a 4-drive RAID1)
> - I did a "btrfs add" on a new drive and then a "btrfs delete missing"
> - The replacement drive failed during the replacement operation, and
> everything went to crap.
> - With some help, I got a kernel patch that allowed me to mount the
> original three drives with TWO missing devices.
> - I added a brand new drive and then did "delete missing" again.  This
> time, the first "delete missing" was successful, but it didn't fully
> balance the drives, and there was another missing device, so I had to
> do a "delete missing" again, and that failed.
>
Just for reference, I've found that it is usually safer to delete the 
missing device first if possible, then add the new one and re-balance. 
There seem to be some edge-cases in the code for deleting missing devices.



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