Re: failed to read block groups: Operation not permitted

[Johannes Hirte <johannes.hirte@datenkhaos.de>]

On 2020 Okt 08, Johannes Hirte wrote:
> On 2020 Okt 06, Qu Wenruo wrote:
> > 
> > 
> > On 2020/10/6 下午5:09, Johannes Hirte wrote:
> > > I recently encountered filesystem damage on a VM. During normal
> > > operation, the filesystem was remounted ro suddenly. Dmesg showed me
> > > some errors about parent transid verify failed. I've forced of the VM
> > > and tried to mount the image on the host, but failed with:
> > > 
> > > [  340.702391] BTRFS info (device loop0p1): disk space caching is enabled
> > > [  340.702393] BTRFS info (device loop0p1): has skinny extents
> > > [  341.815890] BTRFS error (device loop0p1): parent transid verify failed on 152064327680 wanted 323984 found 323888
> > > [  341.831183] BTRFS error (device loop0p1): parent transid verify failed on 152064327680 wanted 323984 found 323888
> > 
> > Your extent tree is corrupted. Metadata CoW is broken.
> > 
> > I don't believe only extent tree get corrupted, other part of your fs
> > can also be corrupted.
> > 
> > > [  341.831194] BTRFS error (device loop0p1): failed to read block groups: -5
> > > [  341.851954] BTRFS error (device loop0p1): open_ctree failed
> > > 
> > > A btrfs check resulted in:
> > > 
> > > btrfs check /dev/loop0p1
> > > Opening filesystem to check...
> > > parent transid verify failed on 152064327680 wanted 323984 found 323888
> > > parent transid verify failed on 152064327680 wanted 323984 found 323888
> > > parent transid verify failed on 152064327680 wanted 323984 found 323888
> > > Ignoring transid failure
> > > leaf parent key incorrect 152064327680
> > > ERROR: failed to read block groups: Operation not permitted
> > > ERROR: cannot open file system
> > > 
> > > The host is running libvirt with kvm, btrfs with RAID1. The VMs are raw
> > > images, with btrfs too. I've switche this VM from io=native to
> > > io=io_uring, and suspect that this caused the damage. All machines are
> > > running kernel 5.8.13.
> > 
> > I'm not sure about the io_uring setup. IIRC as long as you're not using
> > cache=unsafe, it should be safe.
> > 
> > Does the io_uring ignores the flush?
> 
> 
> Putting someone with more knowledge into cc.
> 
> For another VM, I've found several errors in the log of the host machine:
> 
> BTRFS warning (device sda1): direct IO failed ino 5988432 rw 1,2131969 sector 0x123ab840 len 32768 err no 10
> 
> 
> The VM was remounted ro too, like the first one. But in this case the
> filesystem was ok after a check. 

I have to correct this. There are several csum errors on this VM like
this:

BTRFS warning (device vda1): checksum/header error at logical 9660727296 on dev /dev/vda1, physical 6488064: metadata leaf (level 0) in tree 257

-- 
Regards,
  Johannes Hirte