'dump-super -Ffa' from all three devices attached.

'btrfs restore' did appear to recover most of the main data, minus
snapshots, which would have greatly increased the required time and
capacity, since I was recovering to XFS.

'btrfs rescue chunk-recover' ran, but failed to fix anything.
'btrfs rescue super-recover' says all supers are fine.

Initial corruption was due to a hard hang, which didn't leave enough
crumbs to determine the source - might have been btrfs, might have
been nvidia, might have been something completely different.


On 08/15/2019 22:07 +0800, Qu Wenruo wrote:
>>	
>>	
>>	On 2019/8/15 ??????9:52, Tim Walberg wrote:
>>	> Had to wait for 'btrfs recover' to finish before I proceed farther.
>>	> 
>>	> Kernel is 4.19.45, tools are 4.19.1
>>	> 
>>	> File system is a 3-disk RAID10 with WD3003FZEX (WD Black 3TB)
>>	> 
>>	> Output from attempting to mount:
>>	> 
>>	> # mount -o ro,usebackuproot /dev/sdc1 /mnt
>>	> mount: wrong fs type, bad option, bad superblock on /dev/sdc1,
>>	>        missing codepage or helper program, or other error
>>	> 
>>	>        In some cases useful info is found in syslog - try
>>	>        dmesg | tail or so.
>>	> 
>>	> Kernel messages from the mount attempt:
>>	> 
>>	> [Thu Aug 15 08:47:42 2019] BTRFS info (device sdc1): trying to use backup root at mount time
>>	> [Thu Aug 15 08:47:42 2019] BTRFS info (device sdc1): disk space caching is enabled
>>	> [Thu Aug 15 08:47:42 2019] BTRFS info (device sdc1): has skinny extents
>>	> [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): parent transid verify failed on 229846466560 wanted 49749 found 49750
>>	> [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): parent transid verify failed on 229846466560 wanted 49749 found 49750
>>	> [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): failed to read block groups: -5
>>	
>>	Extent tree corruption.
>>	
>>	So if that's the only corruption, you have a very high chance to recover
>>	most of your data.
>>	
>>	Btrfs rescue can work, or you can try the experimental patches which
>>	provides rescue=skip_bg mount option to allow you mount the fs RO and
>>	receive your data (later is way faster than user space rescue)
>>	https://patchwork.kernel.org/project/linux-btrfs/list/?series=130637
>>	
>>	Also, for your dump super output, it doesn't provide too much info.
>>	
>>	You would like to use -Ffa option for more info.
>>	Also, you could also try that on all 3 devices, to find out which one
>>	has lower generation.
>>	
>>	Also, please provide the history of the corruption.
>>	One generation corruptions is a little rare. Is sudden power loss
>>	involved in this case?
>>	
>>	Thanks,
>>	Qu
>>	
>>	> [Thu Aug 15 08:47:42 2019] BTRFS error (device sdc1): open_ctree failed
>>	> 
>>	> Output from 'btrfs check -p /dev/sdc1':
>>	> 
>>	> # btrfs check -p /dev/sdc1
>>	> Opening filesystem to check...
>>	> parent transid verify failed on 229846466560 wanted 49749 found 49750
>>	> Ignoring transid failure
>>	> ERROR: child eb corrupted: parent bytenr=229845336064 item=0 parent level=1 child level=2
>>	> ERROR: cannot open file system
>>	> 
>>	> 
>>	> 
>>	> On 08/15/2019 10:35 +0800, Qu Wenruo wrote:
>>	>>> 	
>>	>>> 	
>>	>>> 	On 2019/8/15 ??????2:32, Tim Walberg wrote:
>>	>>> 	> Most of the recommendations I've found online deal with when "wanted" is
>>	>>> 	> greater than "found", which, if I understand correctly means that one or
>>	>>> 	> more transactions were interrupted/lost before fully committed.
>>	>>> 	
>>	>>> 	No matter what the case is, a proper transaction shouldn't have any tree
>>	>>> 	block overwritten.
>>	>>> 	
>>	>>> 	That means, either the FLUSH/FUA of the hardware/lower block layer is
>>	>>> 	screwed up, or the COW of tree block is already screwed up.
>>	>>> 	
>>	>>> 	> 
>>	>>> 	> Are the recommendations for recovery the same if the system is reporting a
>>	>>> 	> "wanted" that is less than "found"?
>>	>>> 	> 
>>	>>> 	The salvage is no difference than any transid mismatch, no matter if
>>	>>> 	it's larger or smaller.
>>	>>> 	
>>	>>> 	It depends on the tree block.
>>	>>> 	
>>	>>> 	Please provide full dmesg output and btrfs check for further advice.
>>	>>> 	
>>	>>> 	Thanks,
>>	>>> 	Qu
>>	>>> 	
>>	> 
>>	> 
>>	> 
>>	> 
>>	



End of included message



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| Tim Walberg          |
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