zpool import hangs when out of space - Was: zfs pool import hangs on [tx->tx_sync_done_cv]

[Steven Hartland]

----- Original Message ----- 
From: "mark" <Mark.Martinec at ijs.si>
To: <freebsd-fs at freebsd.org>; <freebsd-stable at freebsd.org>
Cc: "FreeBSD Stable" <freebsd-stable at freebsd.org>
Sent: Monday, October 13, 2014 9:55 PM
Subject: Re: zpool import hangs when out of space - Was: zfs pool import hangs on [tx->tx_sync_done_cv]


> On 10/13/2014 22:10, Steven Hartland wrote:
>> So the issue is simply the pool is out of space to perform the import
>> as that process, when not readonly, requires space to write to the pool.
>>
>> The problem with that is that during this process it has the pool lock so
>> any subsequent zpool actions are dead in the water as they will block
>> waiting on that lock.
>>
>> Something to discuss with the openzfs guys, but I would say the import
>> should fail with a no space error.
>>
>> So Mark the mystery is solved, when you upgraded you ran the pool so low
>> on space that it now can't be imported RW as that requires a write.
>>
>>     Regards
>>     Steve
> 
> Thank you both for analysis and effort!
> 
> I can't rule out the possibility that my main system pool
> on a SSD was low on space at some point in time, but the
> three 4 GiB cloned pools (sys1boot and its brothers) were all
> created as a zfs send / receive copies of the main / (root)
> file system and I haven't noticed anything unusual during
> syncing. This syncing was done manually (using zxfer) and
> independently from the upgrade on the system - on a steady/quiet
> system, when the source file system definitely had sufficient
> free space.
> 
> The source file system now shows 1.2 GiB of usage shown
> by df:
>   shiny/ROOT  61758388  1271620  60486768  2%  /
> Seems unlikely that the 1.2 GiB has grown to 4 GiB space
> on a cloned filesystem.
> 
> Will try to import the main two pools after re-creating
> a sane boot pool...

Yer zfs list only shows around 2-3GB used too but zpool list
shows the pool is out of space. Cant rule out an accounting
issue though.

    Regards
    Steve