Re: Crash on btrfs check

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

cheater00 . wrote on 2016/01/15 03:25 +0100:
> Hi guys,
> I have a particularly full btrfs (nearly all of 6TB used on a disk).
> This is different than the fs I've experienced the resize bug on
> recently.
>
> btrfs check crashes on it:
>
> # btrfs check /dev/sdb1
> Checking filesystem on /dev/sdb1
> UUID: 95db96b3-96fe-4a12-810c-27c1dbd30b0d
> checking extents
> extent_io.c:543: __alloc_extent_buffer: Assertion failed.

This means memory allocation failed.

And considering the size of FS, and how btrfsck caches metadata (btrfsck 
will cache all extent info during extent tree check),
it just mean your memory is not big enough to cache them all.


It's already an known problem.
Workaround is to increase your swap size until btrfsck can continue 
without segfault.

Thanks,
Qu

> btrfs[0x80558a3]
> btrfs[0x8092971]
> btrfs(alloc_extent_buffer+0xb7)[0x8093494]
> btrfs(btrfs_find_create_tree_block+0x2b)[0x8083785]
> btrfs(read_tree_block+0x32)[0x808503f]
> btrfs(read_node_slot+0x63)[0x807f430]
> btrfs(btrfs_search_slot+0xb47)[0x8081a28]
> btrfs(btrfs_lookup_extent_info+0xd6)[0x808a0df]
> btrfs[0x806c13a]
> btrfs[0x806d95e]
> btrfs[0x806e5cb]
> btrfs(cmd_check+0x10f8)[0x8070fee]
> btrfs(main+0x14d)[0x8055acb]
> /lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0xb74f0a83]
> btrfs[0x8055af8]
>
>
>
> $ uname -a
> Linux SX20S 4.4.0-040400-generic #201601101930 SMP Mon Jan 11 00:49:33
> UTC 2016 i686 i686 i686 GNU/Linux
>
> $ btrfs --version
> btrfs-progs v4.3
>
> # btrfs fi show /dev/sdb1
> Label: 'A'  uuid: 95db96b3-96fe-4a12-810c-27c1dbd30b0d
>      Total devices 1 FS bytes used 5.41TiB
>      devid    1 size 5.46TiB used 5.46TiB path /dev/sdb1
>
> # btrfs-show-super /dev/sdb1
> superblock: bytenr=65536, device=/dev/sdb1
> ---------------------------------------------------------
> csum            0x116b97f0 [match]
> bytenr            65536
> flags            0x1
>              ( WRITTEN )
> magic            _BHRfS_M [match]
> fsid            95db96b3-96fe-4a12-810c-27c1dbd30b0d
> label            P
> generation        128737
> root            43384832
> sys_array_size        226
> chunk_root_generation    106809
> root_level        1
> chunk_root        20971520
> chunk_root_level    1
> log_root        0
> log_root_transid    0
> log_root_level        0
> total_bytes        6001173463040
> bytes_used        5948325072896
> sectorsize        4096
> nodesize        16384
> leafsize        16384
> stripesize        4096
> root_dir        6
> num_devices        1
> compat_flags        0x0
> compat_ro_flags        0x0
> incompat_flags        0x61
>              ( MIXED_BACKREF |
>                BIG_METADATA |
>                EXTENDED_IREF )
> csum_type        0
> csum_size        4
> cache_generation    128737
> uuid_tree_generation    128737
> dev_item.uuid        e2a8e731-b28c-437b-8cb9-583bb96aea5f
> dev_item.fsid        95db96b3-96fe-4a12-810c-27c1dbd30b0d [match]
> dev_item.type        0
> dev_item.total_bytes    6001173463040
> dev_item.bytes_used    6001173463040
> dev_item.io_align    4096
> dev_item.io_width    4096
> dev_item.sector_size    4096
> dev_item.devid        1
> dev_item.dev_group    0
> dev_item.seek_speed    0
> dev_item.bandwidth    0
> dev_item.generation    0
>
> # btrfs fi usage A
> Overall:
>      Device size:           5.46TiB
>      Device allocated:           5.46TiB
>      Device unallocated:             0.00B
>      Device missing:             0.00B
>      Used:               5.42TiB
>      Free (estimated):          35.41GiB    (min: 35.41GiB)
>      Data ratio:                  1.00
>      Metadata ratio:              2.00
>      Global reserve:         512.00MiB    (used: 0.00B)
>
> Data,single: Size:5.43TiB, Used:5.40TiB
>     /dev/sdb1       5.43TiB
>
> Metadata,single: Size:8.00MiB, Used:0.00B
>     /dev/sdb1       8.00MiB
>
> Metadata,DUP: Size:12.50GiB, Used:11.22GiB
>     /dev/sdb1      25.00GiB
>
> System,single: Size:4.00MiB, Used:0.00B
>     /dev/sdb1       4.00MiB
>
> System,DUP: Size:8.00MiB, Used:608.00KiB
>     /dev/sdb1      16.00MiB
>
> Unallocated:
>     /dev/sdb1         0.00B
>
> dmesg is showing a lot of stuff like this, but it only started doing
> this when I upgraded to linux 4.4, whereas before on 4.3 this didn't
> happen:
>
> [56319.486446] BTRFS critical (device sdb1): entry offset
> 6102519574528, bytes 20480, bitmap no
> [56319.486447] BTRFS critical (device sdb1): entry offset
> 6102527688704, bytes 24576, bitmap no
> [56319.486448] BTRFS critical (device sdb1): entry offset
> 6102528040960, bytes 8192, bitmap no
> [56319.486450] BTRFS critical (device sdb1): entry offset
> 6102536241152, bytes 8192, bitmap no
> [56319.486451] BTRFS critical (device sdb1): entry offset
> 6102561120256, bytes 8192, bitmap no
> [56319.486452] BTRFS critical (device sdb1): entry offset
> 6102590480384, bytes 4096, bitmap no
> [56319.486453] BTRFS critical (device sdb1): entry offset
> 6102620999680, bytes 12288, bitmap no
> [56319.486454] BTRFS critical (device sdb1): entry offset
> 6102633365504, bytes 16384, bitmap no
> [56319.486455] BTRFS info (device sdb1): block group has cluster?: no
> [56319.486456] BTRFS info (device sdb1): 1 blocks of free space at or
> bigger than bytes is
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