Re: Kernel BUG: btrfs send - Incremental backup

[Josef Bacik <jbacik@fb.com>]

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On 03/08/2014 02:35 AM, Swâmi Petaramesh wrote:
> Hi there,
> 
> I tried to perform an incremental backup as described in 
> https://urldefense.proofpoint.com/v1/url?u=https://btrfs.wiki.kernel.org/index.php/Incremental_Backup&k=ZVNjlDMF0FElm4dQtryO4A%3D%3D%0A&r=cKCbChRKsMpTX8ybrSkonQ%3D%3D%0A&m=b7nDm4ij%2BOl6zWwvbxbx%2BbfpaygHhTjGu8dUoBmQj8E%3D%0A&s=550780a62cfd5275891e088623e3d05c78f828ee008ef9b1cb99957ee3752a5d
> between 2 external USB drives,
> 
> The 1st "btrfs send foo/snap1 | btrfs receive bar" went well,
> although it took 5-6 times the time the same workload takes in
> ZFS.
> 
> Then "btrfs send -v -p foo/snap1 foo/snap2 | btrfs receive bar"
> crashed on me.
> 
> After a reboot and retry, I get a KERNEL BUG again :
> 
> 

Well that's odd, I can't think of how this would happen.  Can pull
down btrfs-next and run that and verify you still hit the BUG_ON?  If
you do please apply this patch and re-run and reply with the dmesg.

http://paste.fedoraproject.org/84393/55775013

This will spit out something like this

cur_ino=<NUMBER>, cmp_key objectid=<OTHER NUMBER>

then I need you to unmount your fs and run

btrfs-debug-tree /dev/whatever > blah.txt

You have about 1.5 gig of metadata so that is going to take a while.
Once that is done you want to go through blah.txt and look for

item <number> key (<OTHER NUMBER FROM ABOVE> EXTENT_DATA <number>)

You need to find all of these entries and copy them down, an example
output looks like this

item 1 key (286 EXTENT_DATA 577536) itemoff 3889 itemsize 53
        extent data disk byte 12763136 nr 4096
        extent data offset 0 nr 4096 ram 4096
        extent compression 0

That is what I'm looking for, you will have multiple of these.  Thanks,

Josef

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