Re: btrfstune --convert-to-block-group-tree segfaulted. now filesystem is unmountable

[Konstantinos Skarlatos <k.skarlatos@gmail.com>]

Hello Qu,
thank you for your quick answer!
using your patch, i now get this:

❯ ./btrfstune --convert-to-block-group-tree /dev/sda
ERROR: Corrupted fs, no valid METADATA block group found
ERROR: failed to delete block group item from the old root: -117
ERROR: failed to convert the filesystem to block group tree feature
ERROR: btrfstune failed
extent buffer leak: start 17825576632320 len 16384

On 22/09/2023 12:06 π.μ., Qu Wenruo wrote:
>
>
> On 2023/9/21 22:57, Konstantinos Skarlatos wrote:
>> Hi all,
>> i tried to convert my BTRFS filesystem to block-group-tree but it
>> segfaulted and now the fs is not mountable.
>>
>> ❯ btrfstune --convert-to-block-group-tree /dev/sda
>> [1]    174047 segmentation fault (core dumped)  btrfstune
>> --convert-to-block-group-tree /dev/sda
>>
>>
>> [2531715.190802] btrfstune[174047]: segfault at 1f ip 000055ec409fd198
>> sp 00007ffd0a772eb0 error 4 in btrfstune[55ec409d6000+6a000] likely on
>> CPU 3 (core 2, socket 0)
>> [2531715.190818] Code: 40 00 f3 0f 1e fa 41 56 41 55 49 89 fd 41 54 49
>> 89 f4 55 89 d5 53 48 8b 5f 68 49 89 ee 48 85 db 74 3f 48 8d 74 35 00 0f
>> 1f 00 <48> 8b 43 20 48 8b 4b 28 48 01 c1 49 39 cc 0f 83 8c 00 00 00
>> 48 39
>>
>> [174131]: Process 174047 (btrfstune) of user 0 dumped core.
>>
>>                                                    Stack trace of thread
>> 174047:
>>                                                    #0 
>> 0x000055ec409fd198
>> alloc_extent_buffer (btrfstune + 0x34198)
>>                                                    #1 
>> 0x000055ec409ee4f5
>> read_tree_block (btrfstune + 0x254f5)
>>                                                    #2 
>> 0x000055ec409db5a6
>> read_node_slot (btrfstune + 0x125a6)
>>                                                    #3 
>> 0x000055ec409e6e2d
>> n/a (btrfstune + 0x1de2d)
>>                                                    #4 
>> 0x000055ec409e8a4d
>> n/a (btrfstune + 0x1fa4d)
>>                                                    #5 
>> 0x000055ec409def01
>> btrfs_search_slot (btrfstune + 0x15f01)
>>                                                    #6 
>> 0x000055ec409e9c79
>> btrfs_insert_empty_items (btrfstune + 0x20c79)
>>                                                    #7 
>> 0x000055ec40a0090c
>> n/a (btrfstune + 0x3790c)
>>                                                    #8 
>> 0x000055ec40a05185
>> n/a (btrfstune + 0x3c185)
>>                                                    #9 
>> 0x000055ec40a05c75
>> add_to_free_space_tree (btrfstune + 0x3cc75)
>
> There seems to be something wrong with free space tree code here.
> Not sure which part is causing the problem, the fst or the conversion
> part.
>
>>                                                    #10
>> 0x000055ec40a3ec49
>> n/a (btrfstune + 0x75c49)
>>                                                    #11
>> 0x000055ec409fb52a
>> btrfs_run_delayed_refs (btrfstune + 0x3252a)
>>                                                    #12
>> 0x000055ec40a13091
>> btrfs_commit_transaction (btrfstune + 0x4a091)
>>                                                    #13
>> 0x000055ec409dcfdd
>> convert_to_bg_tree (btrfstune + 0x13fdd)
>>                                                    #14
>> 0x000055ec409d640a
>> main (btrfstune + 0xd40a)
>>                                                    #15
>> 0x00007f44ace27cd0
>> n/a (libc.so.6 + 0x27cd0)
>>                                                    #16
>> 0x00007f44ace27d8a
>> __libc_start_main (libc.so.6 + 0x27d8a)
>>                                                    #17
>> 0x000055ec409d7db5
>> _start (btrfstune + 0xedb5)
>>                                                    ELF object binary
>> architecture: AMD x86-64
>>
>>
>> ❯ btrfstune --convert-from-block-group-tree /dev/sda
>> ERROR: filesystem doesn't have block-group-tree feature
>>
>>
>> ❯ mount /dev/sda /storage/btrfs -o ro
>> mount: /storage/btrfs: wrong fs type, bad option, bad superblock on
>> /dev/sda, missing codepage or helper program, or other error.
>>         dmesg(1) may have more information after failed mount system
>> call.
>>
>> Sep 19 17:18:23 elsinki kernel: BTRFS info (device sda): using crc32c
>> (crc32c-generic) checksum algorithm
>> Sep 19 17:18:23 elsinki kernel: BTRFS error (device sda): unrecognized
>> or unsupported super flag: 274877906944
>> Sep 19 17:18:23 elsinki kernel: BTRFS error (device sda): superblock
>> contains fatal errors
>> Sep 19 17:18:23 elsinki kernel: BTRFS error (device sda): open_ctree
>> failed
>>
>>
>> ❯ btrfstune --convert-to-block-group-tree /dev/sda
>> ERROR: failed to find block group for bytenr 20196285349888
>
> This is the correct way to resume the failed conversion.
>
> But by somehow the block group item seems to be missing from both old
> and new trees.
>
> Mind to test if the attached patch can help?
>
>
>
>> ERROR: failed to convert the filesystem to block group tree feature
>> extent buffer leak: start 17825576632320 len 16384
>>
>> ❯ btrfs filesystem show
>> Label: none  uuid: 5a583d35-3eb2-410b-9044-1ac87a062247
>>          Total devices 3 FS bytes used 9.53TiB
>>          devid    1 size 3.64TiB used 3.64TiB path /dev/sda
>>          devid    2 size 3.64TiB used 3.64TiB path /dev/sdc
>>          devid    3 size 3.64TiB used 3.64TiB path /dev/sdd
>>
>> ❯ btrfs check --mode lowmem /dev/sda
>> Opening filesystem to check...
>> Checking filesystem on /dev/sda
>> UUID: 5a583d35-3eb2-410b-9044-1ac87a062247
>> [1/7] checking root items
>> [2/7] checking extents
>> ERROR: chunk [20197359091712 20198432833536) doesn't have related block
>> group item
> [...]> ERROR: chunk [20674088337408 20674096726016) doesn't have
> related block
>> group item
>
> This shows most of the block groups have been converted.
> Hope the patch can finish the conversion.
>
> Thanks,
> Qu
>>
>>
>> my system specs are:
>> AMD Phenom(tm) II X4 965 Processor @3400MHz
>> 8GB RAM
>>
>> ❯ uname -r
>> 6.4.9-arch1-1
>>
>>