Re: 4.11.3: BTRFS critical (device dm-1): unable to add free space :-17 => btrfs check --repair runs clean

[Marc MERLIN <marc@merlins.org>]

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On Tue, Jun 20, 2017 at 08:44:29AM -0700, Marc MERLIN wrote:
> On Tue, Jun 20, 2017 at 03:36:01PM +0000, Hugo Mills wrote:
> > > Thanks for having a look. Is it a bug, or is it a problem with my storage
> > > subsystem?
> > 
> >    Well, I'd say it's probably a problem with some inconsistent data
> > on the disk. How that data got there is another matter -- it may be
> > due to a bug which wrote the inconsistent data some time ago, and has
> > only now been found out.
>  
> Understood.
> 
> > > "space cache will be invalidated " => doesn't that mean that my cache was
> > > already cleared by check --repair, or are you saying I need to clear it
> > > again?
> > 
> >    I'm never quite sure about that one. :)
> > 
> >    It can't hurt to clear it manually as well.
> 
> Sounds good, done.
 
Except it didn't help :(
It worked for a while, and failed again.

It looks like I'm hitting a persistent bug :(

[   86.383988] BTRFS: device label dshelf2 devid 1 transid 37975 /dev/mapper/dshelf2
[   98.232529] BTRFS info (device dm-1): use lzo compression
[   98.251982] BTRFS info (device dm-1): disk space caching is enabled
[   98.274847] BTRFS info (device dm-1): has skinny extents
[  104.171597] BTRFS info (device dm-1): detected SSD devices, enabling SSD mode
[  165.429894] BTRFS error (device dm-1): Duplicate entries in free space cache, dumping
[  165.455673] BTRFS warning (device dm-1): failed to load free space cache for block group 2039601954816, rebuilding it now
[  234.221435] BTRFS warning (device dm-1): block group 2837392130048 has wrong amount of free space
[  234.249264] BTRFS warning (device dm-1): failed to load free space cache for block group 2837392130048, rebuilding it now
[  234.636396] BTRFS warning (device dm-1): block group 2885173641216 has wrong amount of free space
[  234.664015] BTRFS warning (device dm-1): failed to load free space cache for block group 2885173641216, rebuilding it now
[  242.042940] BTRFS warning (device dm-1): block group 3116565004288 has wrong amount of free space
[  242.071207] BTRFS warning (device dm-1): failed to load free space cache for block group 3116565004288, rebuilding it now
[  273.910918] BTRFS warning (device dm-1): block group 3209980542976 has wrong amount of free space
[  273.937625] BTRFS warning (device dm-1): failed to load free space cache for block group 3209980542976, rebuilding it now
[  298.578615] BTRFS warning (device dm-1): block group 2305889927168 has wrong amount of free space
[  298.605250] BTRFS warning (device dm-1): failed to load free space cache for block group 2305889927168, rebuilding it now
[  873.265687] BTRFS: Transaction aborted (error -17)
[  873.948245] BTRFS: error (device dm-1) in btrfs_run_delayed_refs:2961: errno=-17 Object already exists
[  873.978884] BTRFS info (device dm-1): forced readonly

Given that check --repair ran clean when I ran it yesterday after this first happened,
and I then ran  mount -o clear_cache , the cache got rebuilt, and I got the problem again, 
this is not looking good, seems like a persistent bug :-/

I'm now going to remount this with nospace_cache to see if your guess about
space_cache was correct.
Other suggestions also welcome :)

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/  

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