Filing this bug to track of it and possibly add a solution and automate it with
a testscript.

=====================================
ref:https://www.spinics.net/lists/linux-btrfs/msg67030.html

Hi!
 
I cannot mount my filesystem anymore. The problem started with it going
into read-only mode after the filesystem accidentally became full. At
some point the system crashed and after that I got this error. Is it
possible to recover the filesystem or at least recover some data from
it?

Here is some information from the system:
 
$ uname -a
Linux localhost.localdomain 4.8.6-300.fc25.x86_64 #1 SMP Tue Nov 1 12:36:38 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
 
$ btrfs --version
btrfs-progs v4.6.1
 
$ sudo mount /dev/sda4 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/sda4,
   missing codepage or helper program, or other error
 
   In some cases useful info is found in syslog - try
   dmesg | tail or so.
 
$ sudo btrfs fi show
Label: 'fedora'  uuid: 3ddc9cf1-ff3f-4081-900a-4f732838c31b
   Total devices 1 FS bytes used 208.67GiB
   devid 1 size 230.04GiB used 212.06GiB path /dev/sda4
 
$ dmesg | grep -i btrfs
[ 5.747551] Btrfs loaded, crc32c=crc32c-intel
[ 5.748632] BTRFS: device label fedora devid 1 transid 649633 /dev/sda4
[   48.663727] BTRFS info (device sda4): disk space caching is enabled
[   48.665184] BTRFS error (device sda4): bad tree block start 0 1234052513792
[   48.665194] BTRFS warning (device sda4): failed to read tree root
[   48.680625] BTRFS: open_ctree failed
 
$ sudo btrfs check /dev/sda4
checksum verify failed on 1234052513792 found E4E3BDB6 wanted 00000000
checksum verify failed on 1234052513792 found E4E3BDB6 wanted 00000000
bytenr mismatch, want=1234052513792, have=0
Couldn't read tree root
Couldn't open file system

$ sudo btrfs restore -l /dev/sda4
checksum verify failed on 1234052513792 found E4E3BDB6 wanted 00000000
checksum verify failed on 1234052513792 found E4E3BDB6 wanted 00000000
bytenr mismatch, want=1234052513792, have=0
Couldn't read tree root
Could not open root, trying backup super
checksum verify failed on 1234052513792 found E4E3BDB6 wanted 00000000
checksum verify failed on 1234052513792 found E4E3BDB6 wanted 00000000
bytenr mismatch, want=1234052513792, have=0
Couldn't read tree root
Could not open root, trying backup super
Superblock bytenr is larger than device size
Could not open root, trying backup super

--
Wictor Lund

---------------------------------------
Hi Wictor, Hi List

I'm more or less stuck with the same problem as you. Btrfs on my
external drive got corrupted after I moved a lot of files to it and
would'n mount anymore.
This happened to me in november 2015 and I haven't tried again since
today, as tools and code have matured eventually.

I tried a lot of things, but nothing helped yet :-/

$ uname -a
> Linux apc01 4.10.13-1-ARCH #1 SMP PREEMPT Thu Apr 27 12:15:09 CEST
2017 x86_64 GNU/Linux

$ [root@apc01 ~]# btrfs --version
> btrfs-progs v4.11.1

$ btrfs fi sh
> Label: 'external_0001'  uuid: 6acf5972-91a8-49a1-a5a1-2bcd86b8eb8b
>         Total devices 1 FS bytes used 2.18TiB
>         devid    1 size 3.64TiB used 2.19TiB path /dev/mapper/roverlay

1. cloned the drive with dd
2. attached the cloned drive to my computer and created an writable
overlay (with losetup and dmsetup), so I can test many things without
changing one bit on the cloned drive
3. tried recovery

3a) `mount -t btrfs /dev/mapper/roverlay /mnt`
> BTRFS info (device dm-0): disk space caching is enabled
> BTRFS info (device dm-0): has skinny extents
> BTRFS error (device dm-0): bad tree block start 11851697049360863559
21053440
> BTRFS error (device dm-0): bad tree block start 7989935996922551463
21053440
> BTRFS error (device dm-0): failed to read chunk tree: -5
> BTRFS error (device dm-0): open_ctree failed

3b) `mount -t btrfs -o ro,recovery /dev/mapper/roverlay /mnt`
same as 3a)

3c) `btrfs rescue zero-log /dev/mapper/roverlay`
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found CF3B13F9 wanted 4A9A0385
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> bytenr mismatch, want=21053440, have=11851697049360863559
> Couldn't read chunk tree
> ERROR: cannot open ctree

3d) `btrfs restore /dev/mapper/roverlay /data/recovery`
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found CF3B13F9 wanted 4A9A0385
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> bytenr mismatch, want=21053440, have=11851697049360863559
> Couldn't read chunk tree
> Could not open root, trying backup super
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found CF3B13F9 wanted 4A9A0385
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> bytenr mismatch, want=21053440, have=11851697049360863559
> Couldn't read chunk tree
> Could not open root, trying backup super
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found CF3B13F9 wanted 4A9A0385
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> bytenr mismatch, want=21053440, have=11851697049360863559
> Couldn't read chunk tree
> Could not open root, trying backup super

3e) `btrfs check -s 0 /dev/mapper/roverlay`
> using SB copy 0, bytenr 65536
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found CF3B13F9 wanted 4A9A0385
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> bytenr mismatch, want=21053440, have=11851697049360863559
> Couldn't read chunk tree
> ERROR: cannot open file system

3f) `btrfs check -s 1 /dev/mapper/roverlay`
> using SB copy 1, bytenr 67108864
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found CF3B13F9 wanted 4A9A0385
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> bytenr mismatch, want=21053440, have=11851697049360863559
> Couldn't read chunk tree
> ERROR: cannot open file system

3g) `btrfs check -s 2 /dev/mapper/roverlay`
> using SB copy 2, bytenr 274877906944
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> checksum verify failed on 21053440 found CF3B13F9 wanted 4A9A0385
> checksum verify failed on 21053440 found 42E96418 wanted 277C3E6A
> bytenr mismatch, want=21053440, have=11851697049360863559
> Couldn't read chunk tree
> ERROR: cannot open file system

3h) `btrfs rescue super-recover -v /dev/mapper/roverlay`
> All Devices:
>         Device: id = 1, name = /dev/mapper/roverlay
>
> Before Recovering:
>         [All good supers]:
>                 device name = /dev/mapper/roverlay
>                 superblock bytenr = 65536
>
>                 device name = /dev/mapper/roverlay
>                 superblock bytenr = 67108864
>
>                 device name = /dev/mapper/roverlay
>                 superblock bytenr = 274877906944
>
>         [All bad supers]:
>
> All supers are valid, no need to recover

3i) `btrfs rescue chunk-recover -v /dev/mapper/roverlay`
> All Devices:
>         Device: id = 1, name = /dev/mapper/roverlay
>
> Scanning: 2127447805952 in dev0chunk-recover.c:129:
process_extent_buffer: BUG_ON `exist->nmirrors >= BTRFS_MAX_MIRRORS`
triggered, value 1
> btrfs[0x463150]
> btrfs[0x463fd1]
> /usr/lib/libpthread.so.0(+0x7297)[0x7f0efc75a297]
> /usr/lib/libc.so.6(clone+0x3f)[0x7f0efc49b1ef]
> Aborted (core dumped)

Any more suggestions?

-
andre


=====================================