corruption, bad block, input/output errors - do i run --repair?

[Matt McKinnon <matt@techsquare.com>]

Hi All,

I'm running into some corruption and I wanted to seek out advice on 
whether or not to run btrfs check --repair, or if I should fall back to 
my backup file server, or both.

The system is mountable, and usable.

# uname -a
Linux cbmm-fs 3.17.2-custom #1 SMP Thu Oct 30 14:09:57 EDT 2014 x86_64 
x86_64 x86_64 GNU/Linux

# btrfs --version
Btrfs v3.14.2
# btrfs fi show
Label: none  uuid: 30c15060-8fb4-4926-87d4-f7d08c3033c5
	Total devices 1 FS bytes used 58.92TiB
	devid    1 size 76.40TiB used 59.05TiB path /dev/sda1

# btrfs fi df /home
Data, single: total=58.75TiB, used=58.75TiB
System, DUP: total=32.00MiB, used=2.66MiB
System, single: total=4.00MiB, used=3.68MiB
Metadata, DUP: total=119.00GiB, used=116.63GiB
Metadata, single: total=64.01GiB, used=57.68GiB
GlobalReserve, single: total=512.00MiB, used=0.00B


I did run into some RO snapshot corruption which caused me to run btrfs 
check:

parent transid verify failed on 20809493159936 wanted 
4486137218058286914 found
390978
parent transid verify failed on 20809493159936 wanted 
4486137218058286914 found
390978
Ignoring transid failure
Checking filesystem on /dev/sda1
UUID: 30c15060-8fb4-4926-87d4-f7d08c3033c5
checking extents
bad block 69290357067776
Errors found in extent allocation tree or chunk allocation
checking free space cache
checking fs roots

...

"dir isize wrong" 1 error
"errors 500, file extent discount, nbytes wrong" 14 errors
"errors 2001, no inode item, link count wrong" 257302 errors

...

found 185063071745 bytes used err is 1
total csum bytes: 8428
total tree bytes: 1889284096
total fs tree bytes: 962678784
total extent tree bytes: 159297536
btree space waste bytes: 340014684
file data blocks allocated: 57344
  referenced 57344
Btrfs v3.14.2

Output of a scrub:

ERROR: scrubbing /home failed for device id 1 (Input/output error)
scrub canceled for 30c15060-8fb4-4926-87d4-f7d08c3033c5
         scrub started at Mon Nov  3 06:43:58 2014 and was aborted after 
7613 seconds
         data_extents_scrubbed: 248507555
         tree_extents_scrubbed: 10870729
         data_bytes_scrubbed: 15375990317056
         tree_bytes_scrubbed: 44526505984
         read_errors: 0
         csum_errors: 0
         verify_errors: 0
         no_csum: 15712
         csum_discards: 988018
         super_errors: 0
         malloc_errors: 0
         uncorrectable_errors: 0
         unverified_errors: 0
         corrected_errors: 0
         last_physical: 15425663205376

Output of a balance:

ERROR: error during balancing '/home' - Input/output error
There may be more info in syslog - try dmesg | tail

[501087.506642] ------------[ cut here ]------------
[501087.543971] WARNING: CPU: 5 PID: 31885 at fs/btrfs/relocation.c:925 
build_backref_tree+0x11f0/0x1230 [btrfs]()
[501087.543991] Modules linked in: ipmi_devintf(E) autofs4(E) sb_edac(E) 
edac_core(E) joydev(E) mei_me(E) mei(E) lpc_ich(E) ioatdma(E) ipmi_si(E) 
wmi(E) mac_hid(E) bnep(E) rfcomm(E) bluetooth(E) lp(E) parport(E) 
nfsd(E) nfs_acl(E) auth_rpcgss(E) nfs(E) fscache(E) lockd(E) sunrpc(E) 
ses(E) enclosure(E) hid_generic(E) ahci(E) libahci(E) usbhid(E) hid(E) 
igb(E) dca(E) i2c_algo_bit(E) ptp(E) pps_core(E) megaraid_sas(E) 
btrfs(E) raid6_pq(E) xor(E) libcrc32c(E)
[501087.543995] CPU: 5 PID: 31885 Comm: btrfs Tainted: G      D     E 
3.17.2-custom #1
[501087.543997] Hardware name: Supermicro 
X9DRH-7TF/7F/iTF/iF/X9DRH-7TF/7F/iTF/iF, BIOS 3.0a 12/27/2013
[501087.543999]  000000000000039d ffff88000eadb808 ffffffff8176733c 
0000000000000282
[501087.544001]  0000000000000000 ffff88000eadb848 ffffffff8107163c 
0000000000001000
[501087.544003]  ffff8801d0d9acf0 ffff880497c70380 0000000000000001 
0000000000000001
[501087.544004] Call Trace:
[501087.544014]  [<ffffffff8176733c>] dump_stack+0x46/0x58
[501087.544022]  [<ffffffff8107163c>] warn_slowpath_common+0x8c/0xc0
[501087.544024]  [<ffffffff8107168a>] warn_slowpath_null+0x1a/0x20
[501087.544039]  [<ffffffffa00b4020>] build_backref_tree+0x11f0/0x1230 
[btrfs]
[501087.544052]  [<ffffffffa00b4331>] relocate_tree_blocks+0x2d1/0x690 
[btrfs]
[501087.544060]  [<ffffffff811c1609>] ? kmem_cache_alloc_trace+0x39/0x1f0
[501087.544072]  [<ffffffffa00b54a2>] relocate_block_group+0x202/0x5f0 
[btrfs]
[501087.544083]  [<ffffffffa00b5a40>] 
btrfs_relocate_block_group+0x1b0/0x2d0 [btrfs]
[501087.544098]  [<ffffffffa0088cf5>] 
btrfs_relocate_chunk.isra.62+0x75/0x760 [btrfs]
[501087.544111]  [<ffffffffa0084d86>] ? release_extent_buffer+0x36/0xe0 
[btrfs]
[501087.544124]  [<ffffffffa0085281>] ? free_extent_buffer+0x61/0xc0 [btrfs]
[501087.544136]  [<ffffffffa008d7db>] btrfs_balance+0x8ab/0xf50 [btrfs]
[501087.544150]  [<ffffffffa00985ac>] btrfs_ioctl_balance+0x1cc/0x530 
[btrfs]
[501087.544156]  [<ffffffff811786eb>] ? 
lru_cache_add_active_or_unevictable+0x2b/0xa0
[501087.544168]  [<ffffffffa009aa82>] btrfs_ioctl+0x562/0x1f00 [btrfs]
[501087.544173]  [<ffffffff811e9c0b>] ? putname+0x2b/0x40
[501087.544176]  [<ffffffff811ef193>] ? user_path_at_empty+0x63/0xa0
[501087.544183]  [<ffffffff8105f59c>] ? __do_page_fault+0x28c/0x550
[501087.544187]  [<ffffffff8112528c>] ? acct_account_cputime+0x1c/0x20
[501087.544189]  [<ffffffff811f1106>] do_vfs_ioctl+0x86/0x4f0
[501087.544192]  [<ffffffff810244a5>] ? syscall_trace_enter+0x165/0x280
[501087.544193]  [<ffffffff811f1601>] SyS_ioctl+0x91/0xb0
[501087.544198]  [<ffffffff8176fc7f>] tracesys+0xe1/0xe6
[501087.544199] ---[ end trace e2a77238816656f5 ]---
[501087.579519] parent transid verify failed on 20809493159936 wanted 
4486137218058286914 found 390978


I have been sending incremental snapshot dumps over to an identical file 
server as backups.  Everything checks out OK there.  Do I try to run 
check with --repair first, and fall back to my backup if that fails?

-Matt