I was told some time ago to file a bug on this. When checking btrfs file
system I get below error. I have only one such faulty disk formatted
with BTRFS, so I don't have
any more details about this bug.
root@gamma# btrfs check /dev/sda1
Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
[1/7] checking root items
[2/7] checking extents
check/main.c:4728: add_data_backref: BUG_ON `!back` triggered, value 1
Przerwane

root@gamma# btrfs check /dev/sda1 --repair
enabling repair mode
Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
[1/7] checking root items
Fixed 0 roots.
[2/7] checking extents
memory allocation failed

[...]

The only way for this BUG_ON to happen is to exhaust available memory.  The
message should be more graceful, indeed.

Could you please try --mode=lowmem ?  Besides requiring drastically less
memory, it's also a cleanish rewrite of the code, and seems quite mature
already.  Thus, it's likely it can succeed where --mode=original fails.


Meow!

Yes! It succeeded, although it took three days to finish, while copying
all data with rsync took 14 hours:

Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
[1/7] checking root items
[2/7] checking extents
[3/7] checking free space cache
[4/7] checking fs roots
[5/7] checking only csums items (without verifying data)
[6/7] checking root refs done with fs roots in lowmem mode, skipping
[7/7] checking quota groups skipped (not enabled on this FS)
found 1515751325696 bytes used, no error found
total csum bytes: 1407037120
total tree bytes: 74490691584
total fs tree bytes: 71160676352
total extent tree bytes: 1746927616
btree space waste bytes: 15397847798
file data blocks allocated: 5376395280384
  referenced 5376395280384




Then cleared v2 free space cache:

# btrfs check --mode=lowmem --clear-space-cache v2 --progress /dev/sda1
Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969



And with "v1" i got an error:

# btrfs check --mode=lowmem --clear-space-cache v1 --progress /dev/sda1
Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
Failed to find [1198869790720, 168, 16384]
btrfs unable to find ref byte nr 1198869807104 parent 0 root 2 owner 0
offset 0
transaction.c:168: btrfs_commit_transaction: BUG_ON `ret` triggered,
value -5
btrfs(+0x3c0ad)[0x4900ad]
btrfs(btrfs_commit_transaction+0x68)[0x4904bb]
btrfs(btrfs_clear_free_space_cache+0x3d8)[0x4845ef]
btrfs(+0x4fb0f)[0x4a3b0f]
btrfs(cmd_check+0x716)[0x4b1dd9]
btrfs(main+0x22c)[0x460edc]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0xb7c9bb41]
btrfs(_start+0x31)[0x460f21]
Przerwane


Same failure:

# btrfs check --clear-space-cache v1 /dev/sda1
Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
Failed to find [1198869790720, 168, 16384]
btrfs unable to find ref byte nr 1198869807104 parent 0 root 2 owner 0
offset 0
transaction.c:168: btrfs_commit_transaction: BUG_ON `ret` triggered,
value -5
btrfs(+0x3c0ad)[0x47d0ad]
btrfs(btrfs_commit_transaction+0x68)[0x47d4bb]
btrfs(btrfs_clear_free_space_cache+0x3d8)[0x4715ef]
btrfs(+0x4fb0f)[0x490b0f]
btrfs(cmd_check+0x716)[0x49edd9]
btrfs(main+0x22c)[0x44dedc]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0xb7c5bb41]
btrfs(_start+0x31)[0x44df21]
Przerwane



# btrfs fi show /dev/sda1
Label: none  uuid: 666a7089-d716-44ff-8081-56b969b58eff
     Total devices 1 FS bytes used 1.38TiB
     devid    1 size 1.82TiB used 1.82TiB path /dev/sda1

I made further tests.

This system runs since 2018-02, so maybe it is spoiled from some bugs in
debian stretch (ver 9).



Checking disk took 68 hours:


# time btrfs check --mode=lowmem --progress /dev/sda1

Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
[1/7] checking root items                      (0:04:06 elapsed, 10279815 items checked)
ERROR: extent[1198869807104 16384] backref lost (owner: 2, level: 0) root 2s checked)
ERROR: extent [1198864121856 16384] referencer bytenr mismatch, wanted: 1198864121856, have: 1198869807104
[2/7] checking extents                         (16:20:19 elapsed, 6306997 items checked)
ERROR: errors found in extent allocation tree or chunk allocation
cache and super generation don't match, space cache will be invalidated
[3/7] checking free space cache                (0:00:00 elapsed)
[4/7] checking fs roots                        (51:57:16 elapsed, 4271043 items checked)
[5/7] checking csums (without verifying data)  (0:09:33 elapsed, 898322 items checked)
[6/7] checking root refs done with fs roots in lowmem mode, skipping
[7/7] checking quota groups skipped (not enabled on this FS)
found 1515733991424 bytes used, error(s) found
total csum bytes: 1407037120
total tree bytes: 74490642432
total fs tree bytes: 71160676352
total extent tree bytes: 1746911232
btree space waste bytes: 15397830986
file data blocks allocated: 5376377978880
  referenced 5376377978880

real    4111m27,540s
user    3268m33,968s
sys     24m22,004s




Errors in dmesg while checking:

[11443.813297] BTRFS warning (device sda1): block group 2211400646656 has wrong amount of free space
[11443.813299] BTRFS warning (device sda1): failed to load free space cache for block group 2211400646656, rebuilding it now
[17145.954563] perf: interrupt took too long (11171 > 4916), lowering kernel.perf_event_max_sample_rate to 17750
[17593.634367] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 1.099 msecs
[17750.815402] perf: interrupt took too long (16147 > 13963), lowering kernel.perf_event_max_sample_rate to 12250
[38731.197299] BTRFS warning (device sda1): block group 1434548436992 has wrong amount of free space
[38731.197302] BTRFS warning (device sda1): failed to load free space cache for block group 1434548436992, rebuilding it now
[38731.205956] BTRFS warning (device sda1): block group 1435622178816 has wrong amount of free space
[38731.205957] BTRFS warning (device sda1): failed to load free space cache for block group 1435622178816, rebuilding it now
[38731.247236] BTRFS warning (device sda1): block group 1436695920640 has wrong amount of free space
[38731.247238] BTRFS warning (device sda1): failed to load free space cache for block group 1436695920640, rebuilding it now
[53198.046259] BTRFS warning (device sda1): block group 1804989366272 has wrong amount of free space
[53198.046276] BTRFS warning (device sda1): failed to load free space cache for block group 1804989366272, rebuilding it now
[53607.550637] BTRFS warning (device sda1): block group 1843107201024 has wrong amount of free space
[53607.550639] BTRFS warning (device sda1): failed to load free space cache for block group 1843107201024, rebuilding it now
[54399.231065] INFO: NMI handler (perf_event_nmi_handler) took too long to run: 1.224 msecs
[55476.396901] BTRFS warning (device sda1): block group 1921490354176 has wrong amount of free space
[55476.396904] BTRFS warning (device sda1): failed to load free space cache for block group 1921490354176, rebuilding it now
[55921.074396] BTRFS warning (device sda1): block group 1947260157952 has wrong amount of free space
[55921.074400] BTRFS warning (device sda1): failed to load free space cache for block group 1947260157952, rebuilding it now



Errors while mounting and trying to write to disk:

[555578.836138] BTRFS info (device sda1): trying to use backup root at mount time
[555578.836141] BTRFS info (device sda1): disabling disk space caching
[555578.836143] BTRFS info (device sda1): force clearing of disk cache
[555578.836144] BTRFS info (device sda1): has skinny extents
[555591.702301] BTRFS info (device sda1): checking UUID tree
[663200.501471] BTRFS info (device sdc1): disk space caching is enabled
[663200.501473] BTRFS info (device sdc1): has skinny extents
[833031.126537] BTRFS info (device sda1): disk space caching is enabled
[833031.126539] BTRFS info (device sda1): has skinny extents
[833044.239191] BTRFS info (device sda1): checking UUID tree
[833267.737626] WARNING: CPU: 1 PID: 27878 at fs/btrfs/extent-tree.c:6795 __btrfs_free_extent+0x6b2/0x940 [btrfs]
[833267.737628] Modules linked in: soundcore dm_mod nouveau kvm_intel mxm_wmi wmi video kvm ttm drm_kms_helper drm sg evdev serio_raw i2c_algo_bit iTCO_wdt iTCO_vendor_support pcspkr irqbypass pcc_cpufreq acpi_cpufreq button coretemp loop ip_tables x_tables autofs4 reiserfs btrfs zstd_decompress zstd_compress xxhash raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c crc32c_generic raid1 raid0 multipath linear md_mod sd_mod ata_generic ahci pata_jmicron ata_piix libahci ehci_pci uhci_hcd ehci_hcd i2c_i801 libata lpc_ich r8169 realtek libphy scsi_mod usbcore usb_common
[833267.737674] CPU: 1 PID: 27878 Comm: btrfs-transacti Not tainted 4.19.0-5-686-pae #1 Debian 4.19.37-5+deb10u2
[833267.737675] Hardware name: Gigabyte Technology Co., Ltd. P35T-DQ6/P35T-DQ6, BIOS F5 02/27/2008
[833267.737692] EIP: __btrfs_free_extent+0x6b2/0x940 [btrfs]
[833267.737694] Code: ff 8b 4d c4 e9 f7 fe ff ff 8d b4 26 00 00 00 00 0f 0b 8d b6 00 00 00 00 8b 47 20 c7 45 8c 01 00 00 00 89 45 9c e9 cf fd ff ff <0f> 0b 8b 07 e8 a5 31 00 00 ff 75 24 ff 75 20 ff 75 1c ff 75 18 ff
[833267.737695] EAX: fffffffe EBX: 00000000 ECX: dcaa5d18 EDX: fffffffe
[833267.737696] ESI: 22358000 EDI: dbaa11e0 EBP: dcaa5e08 ESP: dcaa5d88
[833267.737698] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246
[833267.737699] CR0: 80050033 CR2: 0058f054 CR3: 24e30000 CR4: 000006f0
[833267.737700] Call Trace:
[833267.737707]  ? discard_slab+0x2c/0x40
[833267.737725]  __btrfs_run_delayed_refs+0x20d/0x1030 [btrfs]
[833267.737729]  ? kmem_cache_free+0x172/0x190
[833267.737743]  ? btrfs_free_path.part.28+0x1c/0x20 [btrfs]
[833267.737757]  ? btrfs_free_path.part.28+0x1c/0x20 [btrfs]
[833267.737774]  btrfs_run_delayed_refs+0x6f/0x150 [btrfs]
[833267.737793]  btrfs_commit_transaction+0x270/0x970 [btrfs]
[833267.737812]  ? start_transaction+0x81/0x420 [btrfs]
[833267.737816]  ? __next_timer_interrupt+0xc0/0xc0
[833267.737834]  transaction_kthread+0x175/0x1b0 [btrfs]
[833267.737837]  kthread+0xf0/0x110
[833267.737855]  ? btrfs_cleanup_transaction+0x4c0/0x4c0 [btrfs]
[833267.737857]  ? kthread_associate_blkcg+0xa0/0xa0
[833267.737861]  ret_from_fork+0x2e/0x38
[833267.737863] ---[ end trace 2b4d9362179b417f ]---
[833267.737867] BTRFS info (device sda1): leaf 136331264 gen 221611 total ptrs 203 free space 4509 owner 2
[833267.737869] 	item 0 key (1198866366464 169 0) itemoff 16250 itemsize 33
[833267.737870] 		extent refs 1 gen 221219 flags 2
[833267.737871] 		ref#0: tree block backref root 2
[833267.737874] 	item 1 key (1198866382848 169 0) itemoff 16217 itemsize 33
[833267.737875] 		extent refs 1 gen 221219 flags 2
[833267.737876] 		ref#0: tree block backref root 2
[833267.737878] 	item 2 key (1198866399232 169 0) itemoff 16184 itemsize 33
[833267.737879] 		extent refs 1 gen 221219 flags 2
[833267.737880] 		ref#0: tree block backref root 2
[833267.737882] 	item 3 key (1198866415616 169 0) itemoff 16151 itemsize 33
[833267.737883] 		extent refs 1 gen 221219 flags 2
[833267.737884] 		ref#0: tree block backref root 2
[833267.737886] 	item 4 key (1198866432000 169 0) itemoff 16118 itemsize 33
[833267.737887] 		extent refs 1 gen 221219 flags 2
[833267.737888] 		ref#0: tree block backref root 2
[833267.737890] 	item 5 key (1198866448384 169 0) itemoff 16085 itemsize 33
[833267.737892] 		extent refs 1 gen 221219 flags 2
[833267.737892] 		ref#0: tree block backref root 2
[833267.737894] 	item 6 key (1198866481152 169 0) itemoff 16052 itemsize 33
[833267.737896] 		extent refs 1 gen 221219 flags 2
[833267.737896] 		ref#0: tree block backref root 2
[833267.737899] 	item 7 key (1198866497536 169 0) itemoff 16019 itemsize 33
[833267.737900] 		extent refs 1 gen 221219 flags 2
[833267.737900] 		ref#0: tree block backref root 2
[833267.737903] 	item 8 key (1198866513920 169 0) itemoff 15986 itemsize 33
[833267.737904] 		extent refs 1 gen 221219 flags 2
[833267.737905] 		ref#0: tree block backref root 2
[833267.737907] 	item 9 key (1198866530304 169 0) itemoff 15953 itemsize 33
[833267.737908] 		extent refs 1 gen 221219 flags 2
[833267.737909] 		ref#0: tree block backref root 2
[833267.737911] 	item 10 key (1198866546688 169 0) itemoff 15920 itemsize 33
[833267.737912] 		extent refs 1 gen 221219 flags 2
[833267.737913] 		ref#0: tree block backref root 2
[833267.737915] 	item 11 key (1198866628608 169 0) itemoff 15887 itemsize 33
[833267.737916] 		extent refs 1 gen 221219 flags 2
[833267.737917] 		ref#0: tree block backref root 2
[833267.737919] 	item 12 key (1198866644992 169 0) itemoff 15854 itemsize 33
[833267.737920] 		extent refs 1 gen 221219 flags 2
[833267.737921] 		ref#0: tree block backref root 2
[833267.737923] 	item 13 key (1198866661376 169 0) itemoff 15821 itemsize 33
[833267.737925] 		extent refs 1 gen 221219 flags 2
[833267.737925] 		ref#0: tree block backref root 2
[833267.737928] 	item 14 key (1198866677760 169 0) itemoff 15788 itemsize 33
[833267.737929] 		extent refs 1 gen 221219 flags 2
[833267.737930] 		ref#0: tree block backref root 2
[833267.737932] 	item 15 key (1198866694144 169 0) itemoff 15755 itemsize 33
[833267.737933] 		extent refs 1 gen 221219 flags 2
[833267.737934] 		ref#0: tree block backref root 2
[833267.737936] 	item 16 key (1198866710528 169 0) itemoff 15722 itemsize 33
[833267.737937] 		extent refs 1 gen 221219 flags 2
[833267.737938] 		ref#0: tree block backref root 2
[833267.737940] 	item 17 key (1198866726912 169 0) itemoff 15689 itemsize 33
[833267.737941] 		extent refs 1 gen 221219 flags 2
[833267.737942] 		ref#0: tree block backref root 2
[833267.737944] 	item 18 key (1198866743296 169 0) itemoff 15656 itemsize 33
[833267.737945] 		extent refs 1 gen 221219 flags 2
[833267.737946] 		ref#0: tree block backref root 2
[833267.737948] 	item 19 key (1198866759680 169 0) itemoff 15623 itemsize 33
[833267.737949] 		extent refs 1 gen 221219 flags 2
[833267.737950] 		ref#0: tree block backref root 2
[833267.737952] 	item 20 key (1198866776064 169 0) itemoff 15590 itemsize 33
[833267.737954] 		extent refs 1 gen 221219 flags 2
[833267.737954] 		ref#0: tree block backref root 2
[833267.737956] 	item 21 key (1198866792448 169 0) itemoff 15557 itemsize 33
[833267.737958] 		extent refs 1 gen 221219 flags 2
[833267.737958] 		ref#0: tree block backref root 2
[833267.737961] 	item 22 key (1198866808832 169 0) itemoff 15524 itemsize 33
[833267.737962] 		extent refs 1 gen 221219 flags 2
[833267.737962] 		ref#0: tree block backref root 2
[833267.737965] 	item 23 key (1198866825216 169 0) itemoff 15491 itemsize 33
[833267.737966] 		extent refs 1 gen 221219 flags 2
[833267.737966] 		ref#0: tree block backref root 2
[833267.737969] 	item 24 key (1198866841600 169 0) itemoff 15458 itemsize 33
[833267.737970] 		extent refs 1 gen 221219 flags 2
[833267.737971] 		ref#0: tree block backref root 2
[833267.737973] 	item 25 key (1198866857984 169 0) itemoff 15425 itemsize 33
[833267.737974] 		extent refs 1 gen 221219 flags 2
[833267.737975] 		ref#0: tree block backref root 2
[833267.737977] 	item 26 key (1198866874368 169 0) itemoff 15392 itemsize 33
[833267.737978] 		extent refs 1 gen 221219 flags 2
[833267.737979] 		ref#0: tree block backref root 2
[833267.737981] 	item 27 key (1198866890752 169 0) itemoff 15359 itemsize 33
[833267.737982] 		extent refs 1 gen 221221 flags 2
[833267.737983] 		ref#0: tree block backref root 2
[833267.737985] 	item 28 key (1198866907136 169 0) itemoff 15326 itemsize 33
[833267.737986] 		extent refs 1 gen 221273 flags 2
[833267.737987] 		ref#0: tree block backref root 2
[833267.737989] 	item 29 key (1198866923520 169 0) itemoff 15293 itemsize 33
[833267.737991] 		extent refs 1 gen 221273 flags 2
[833267.737991] 		ref#0: tree block backref root 2
[833267.737994] 	item 30 key (1198866939904 169 0) itemoff 15260 itemsize 33
[833267.737995] 		extent refs 1 gen 221219 flags 2
[833267.737995] 		ref#0: tree block backref root 2
[833267.737998] 	item 31 key (1198866956288 169 0) itemoff 15227 itemsize 33
[833267.737999] 		extent refs 1 gen 221219 flags 2
[833267.738000] 		ref#0: tree block backref root 2
[833267.738002] 	item 32 key (1198866972672 169 0) itemoff 15194 itemsize 33
[833267.738003] 		extent refs 1 gen 221219 flags 2
[833267.738004] 		ref#0: tree block backref root 2
[833267.738006] 	item 33 key (1198866989056 169 0) itemoff 15161 itemsize 33
[833267.738007] 		extent refs 1 gen 221219 flags 2
[833267.738008] 		ref#0: tree block backref root 2
[833267.738010] 	item 34 key (1198867005440 169 0) itemoff 15128 itemsize 33
[833267.738011] 		extent refs 1 gen 221219 flags 2
[833267.738012] 		ref#0: tree block backref root 2
[833267.738014] 	item 35 key (1198867021824 169 0) itemoff 15095 itemsize 33
[833267.738015] 		extent refs 1 gen 221219 flags 2
[833267.738016] 		ref#0: tree block backref root 2
[833267.738018] 	item 36 key (1198867038208 169 0) itemoff 15062 itemsize 33
[833267.738020] 		extent refs 1 gen 221219 flags 2
[833267.738020] 		ref#0: tree block backref root 2
[833267.738022] 	item 37 key (1198867054592 169 0) itemoff 15029 itemsize 33
[833267.738024] 		extent refs 1 gen 221219 flags 2
[833267.738024] 		ref#0: tree block backref root 2
[833267.738027] 	item 38 key (1198867087360 169 0) itemoff 14996 itemsize 33
[833267.738028] 		extent refs 1 gen 221219 flags 2
[833267.738028] 		ref#0: tree block backref root 2
[833267.738031] 	item 39 key (1198867103744 169 0) itemoff 14963 itemsize 33
[833267.738032] 		extent refs 1 gen 221219 flags 2
[833267.738033] 		ref#0: tree block backref root 2
[833267.738035] 	item 40 key (1198867120128 169 0) itemoff 14930 itemsize 33
[833267.738036] 		extent refs 1 gen 221219 flags 2
[833267.738037] 		ref#0: tree block backref root 2
[833267.738039] 	item 41 key (1198867136512 169 0) itemoff 14897 itemsize 33
[833267.738040] 		extent refs 1 gen 221219 flags 2
[833267.738041] 		ref#0: tree block backref root 2
[833267.738043] 	item 42 key (1198867169280 169 0) itemoff 14864 itemsize 33
[833267.738044] 		extent refs 1 gen 221219 flags 2
[833267.738045] 		ref#0: tree block backref root 2
[833267.738047] 	item 43 key (1198867185664 169 0) itemoff 14831 itemsize 33
[833267.738048] 		extent refs 1 gen 221219 flags 2
[833267.738049] 		ref#0: tree block backref root 2
[833267.738051] 	item 44 key (1198867202048 169 0) itemoff 14798 itemsize 33
[833267.738052] 		extent refs 1 gen 221219 flags 2
[833267.738053] 		ref#0: tree block backref root 2
[833267.738055] 	item 45 key (1198867218432 169 0) itemoff 14765 itemsize 33
[833267.738057] 		extent refs 1 gen 221219 flags 2
[833267.738057] 		ref#0: tree block backref root 2
[833267.738059] 	item 46 key (1198867234816 169 0) itemoff 14732 itemsize 33
[833267.738061] 		extent refs 1 gen 9305 flags 258
[833267.738061] 		ref#0: shared block backref parent 1182567350272
[833267.738064] 	item 47 key (1198867251200 169 0) itemoff 14699 itemsize 33
[833267.738065] 		extent refs 1 gen 9305 flags 258
[833267.738066] 		ref#0: shared block backref parent 1182567350272
[833267.738068] 	item 48 key (1198867267584 169 0) itemoff 14666 itemsize 33
[833267.738070] 		extent refs 1 gen 221221 flags 2
[833267.738070] 		ref#0: tree block backref root 2
[833267.738073] 	item 49 key (1198867283968 169 0) itemoff 14633 itemsize 33
[833267.738074] 		extent refs 1 gen 9305 flags 258
[833267.738075] 		ref#0: shared block backref parent 1182567350272
[833267.738077] 	item 50 key (1198867300352 169 0) itemoff 14600 itemsize 33
[833267.738078] 		extent refs 1 gen 221219 flags 2
[833267.738079] 		ref#0: tree block backref root 2
[833267.738081] 	item 51 key (1198867316736 169 0) itemoff 14567 itemsize 33
[833267.738082] 		extent refs 1 gen 221289 flags 2
[833267.738083] 		ref#0: tree block backref root 2
[833267.738085] 	item 52 key (1198867333120 169 0) itemoff 14534 itemsize 33
[833267.738087] 		extent refs 1 gen 9305 flags 258
[833267.738087] 		ref#0: shared block backref parent 1182567350272
[833267.738090] 	item 53 key (1198867349504 169 0) itemoff 14501 itemsize 33
[833267.738091] 		extent refs 1 gen 9305 flags 258
[833267.738092] 		ref#0: shared block backref parent 1182567350272
[833267.738094] 	item 54 key (1198867365888 169 0) itemoff 14468 itemsize 33
[833267.738095] 		extent refs 1 gen 9305 flags 258
[833267.738096] 		ref#0: shared block backref parent 1182567350272
[833267.738098] 	item 55 key (1198867382272 169 0) itemoff 14435 itemsize 33
[833267.738099] 		extent refs 1 gen 221219 flags 2
[833267.738100] 		ref#0: tree block backref root 2
[833267.738102] 	item 56 key (1198867398656 169 0) itemoff 14402 itemsize 33
[833267.738104] 		extent refs 1 gen 221219 flags 2
[833267.738104] 		ref#0: tree block backref root 2
[833267.738107] 	item 57 key (1198867415040 169 0) itemoff 14369 itemsize 33
[833267.738108] 		extent refs 1 gen 221219 flags 2
[833267.738108] 		ref#0: tree block backref root 2
[833267.738111] 	item 58 key (1198867431424 169 0) itemoff 14336 itemsize 33
[833267.738112] 		extent refs 1 gen 221219 flags 2
[833267.738113] 		ref#0: tree block backref root 2
[833267.738115] 	item 59 key (1198867447808 169 0) itemoff 14303 itemsize 33
[833267.738116] 		extent refs 1 gen 221219 flags 2
[833267.738117] 		ref#0: tree block backref root 2
[833267.738119] 	item 60 key (1198867464192 169 0) itemoff 14270 itemsize 33
[833267.738120] 		extent refs 1 gen 221219 flags 2
[833267.738121] 		ref#0: tree block backref root 2
[833267.738123] 	item 61 key (1198867480576 169 0) itemoff 14237 itemsize 33
[833267.738124] 		extent refs 1 gen 9305 flags 258
[833267.738125] 		ref#0: shared block backref parent 1182567350272
[833267.738127] 	item 62 key (1198867496960 169 0) itemoff 14204 itemsize 33
[833267.738129] 		extent refs 1 gen 221219 flags 2
[833267.738129] 		ref#0: tree block backref root 2
[833267.738132] 	item 63 key (1198867513344 169 0) itemoff 14171 itemsize 33
[833267.738133] 		extent refs 1 gen 221219 flags 2
[833267.738134] 		ref#0: tree block backref root 2
[833267.738136] 	item 64 key (1198867529728 169 0) itemoff 14138 itemsize 33
[833267.738137] 		extent refs 1 gen 221219 flags 2
[833267.738138] 		ref#0: tree block backref root 2
[833267.738140] 	item 65 key (1198867546112 169 0) itemoff 14105 itemsize 33
[833267.738141] 		extent refs 1 gen 221219 flags 2
[833267.738142] 		ref#0: tree block backref root 2
[833267.738144] 	item 66 key (1198867562496 169 0) itemoff 14072 itemsize 33
[833267.738145] 		extent refs 1 gen 221219 flags 2
[833267.738146] 		ref#0: tree block backref root 2
[833267.738148] 	item 67 key (1198867578880 169 0) itemoff 14039 itemsize 33
[833267.738149] 		extent refs 1 gen 221219 flags 2
[833267.738150] 		ref#0: tree block backref root 2
[833267.738152] 	item 68 key (1198867595264 169 0) itemoff 14006 itemsize 33
[833267.738153] 		extent refs 1 gen 221219 flags 2
[833267.738154] 		ref#0: tree block backref root 2
[833267.738156] 	item 69 key (1198867611648 169 0) itemoff 13973 itemsize 33
[833267.738157] 		extent refs 1 gen 221219 flags 2
[833267.738158] 		ref#0: tree block backref root 2
[833267.738160] 	item 70 key (1198867628032 169 0) itemoff 13940 itemsize 33
[833267.738161] 		extent refs 1 gen 221219 flags 2
[833267.738162] 		ref#0: tree block backref root 2
[833267.738164] 	item 71 key (1198867644416 169 0) itemoff 13907 itemsize 33
[833267.738166] 		extent refs 1 gen 221219 flags 2
[833267.738166] 		ref#0: tree block backref root 2
[833267.738168] 	item 72 key (1198867660800 169 0) itemoff 13874 itemsize 33
[833267.738170] 		extent refs 1 gen 221219 flags 2
[833267.738170] 		ref#0: tree block backref root 2
[833267.738173] 	item 73 key (1198867677184 169 0) itemoff 13841 itemsize 33
[833267.738174] 		extent refs 1 gen 221219 flags 2
[833267.738174] 		ref#0: tree block backref root 2
[833267.738177] 	item 74 key (1198867693568 169 0) itemoff 13808 itemsize 33
[833267.738178] 		extent refs 1 gen 9222 flags 258
[833267.738179] 		ref#0: tree block backref root 2535
[833267.738181] 	item 75 key (1198867709952 169 0) itemoff 13775 itemsize 33
[833267.738182] 		extent refs 1 gen 221219 flags 2
[833267.738183] 		ref#0: tree block backref root 2
[833267.738185] 	item 76 key (1198867759104 169 0) itemoff 13742 itemsize 33
[833267.738186] 		extent refs 1 gen 221219 flags 2
[833267.738187] 		ref#0: tree block backref root 2
[833267.738189] 	item 77 key (1198867775488 169 0) itemoff 13709 itemsize 33
[833267.738190] 		extent refs 1 gen 221219 flags 2
[833267.738191] 		ref#0: tree block backref root 2
[833267.738193] 	item 78 key (1198867791872 169 0) itemoff 13676 itemsize 33
[833267.738195] 		extent refs 1 gen 221221 flags 2
[833267.738195] 		ref#0: tree block backref root 2
[833267.738197] 	item 79 key (1198867808256 169 0) itemoff 13643 itemsize 33
[833267.738199] 		extent refs 1 gen 221219 flags 2
[833267.738199] 		ref#0: tree block backref root 2
[833267.738202] 	item 80 key (1198867824640 169 0) itemoff 13610 itemsize 33
[833267.738203] 		extent refs 1 gen 221219 flags 2
[833267.738203] 		ref#0: tree block backref root 2
[833267.738206] 	item 81 key (1198867841024 169 0) itemoff 13577 itemsize 33
[833267.738207] 		extent refs 1 gen 221219 flags 2
[833267.738207] 		ref#0: tree block backref root 2
[833267.738210] 	item 82 key (1198867857408 169 0) itemoff 13544 itemsize 33
[833267.738211] 		extent refs 1 gen 221219 flags 2
[833267.738212] 		ref#0: tree block backref root 2
[833267.738214] 	item 83 key (1198867873792 169 0) itemoff 13511 itemsize 33
[833267.738215] 		extent refs 1 gen 221219 flags 2
[833267.738216] 		ref#0: tree block backref root 2
[833267.738218] 	item 84 key (1198867890176 169 0) itemoff 13478 itemsize 33
[833267.738219] 		extent refs 1 gen 221219 flags 2
[833267.738220] 		ref#0: tree block backref root 2
[833267.738222] 	item 85 key (1198867906560 169 0) itemoff 13445 itemsize 33
[833267.738223] 		extent refs 1 gen 221219 flags 2
[833267.738224] 		ref#0: tree block backref root 2
[833267.738226] 	item 86 key (1198867922944 169 0) itemoff 13412 itemsize 33
[833267.738227] 		extent refs 1 gen 221219 flags 2
[833267.738228] 		ref#0: tree block backref root 2
[833267.738230] 	item 87 key (1198867939328 169 0) itemoff 13379 itemsize 33
[833267.738231] 		extent refs 1 gen 221219 flags 2
[833267.738232] 		ref#0: tree block backref root 2
[833267.738234] 	item 88 key (1198867955712 169 0) itemoff 13346 itemsize 33
[833267.738236] 		extent refs 1 gen 221219 flags 2
[833267.738236] 		ref#0: tree block backref root 2
[833267.738238] 	item 89 key (1198867972096 169 0) itemoff 13313 itemsize 33
[833267.738240] 		extent refs 1 gen 221219 flags 2
[833267.738240] 		ref#0: tree block backref root 2
[833267.738243] 	item 90 key (1198867988480 169 0) itemoff 13280 itemsize 33
[833267.738244] 		extent refs 1 gen 221219 flags 2
[833267.738244] 		ref#0: tree block backref root 2
[833267.738247] 	item 91 key (1198868004864 169 0) itemoff 13247 itemsize 33
[833267.738248] 		extent refs 1 gen 221219 flags 2
[833267.738249] 		ref#0: tree block backref root 2
[833267.738251] 	item 92 key (1198868021248 169 0) itemoff 13214 itemsize 33
[833267.738252] 		extent refs 1 gen 221219 flags 2
[833267.738253] 		ref#0: tree block backref root 2
[833267.738255] 	item 93 key (1198868037632 169 0) itemoff 13181 itemsize 33
[833267.738256] 		extent refs 1 gen 221219 flags 2
[833267.738257] 		ref#0: tree block backref root 2
[833267.738259] 	item 94 key (1198868054016 169 0) itemoff 13148 itemsize 33
[833267.738260] 		extent refs 1 gen 221219 flags 2
[833267.738261] 		ref#0: tree block backref root 2
[833267.738263] 	item 95 key (1198868086784 169 0) itemoff 13115 itemsize 33
[833267.738264] 		extent refs 1 gen 221219 flags 2
[833267.738265] 		ref#0: tree block backref root 2
[833267.738267] 	item 96 key (1198868119552 169 0) itemoff 13082 itemsize 33
[833267.738268] 		extent refs 1 gen 221219 flags 2
[833267.738269] 		ref#0: tree block backref root 2
[833267.738271] 	item 97 key (1198868135936 169 0) itemoff 13049 itemsize 33
[833267.738272] 		extent refs 1 gen 9305 flags 258
[833267.738273] 		ref#0: shared block backref parent 1201690198016
[833267.738276] 	item 98 key (1198868152320 169 0) itemoff 13016 itemsize 33
[833267.738277] 		extent refs 1 gen 221219 flags 2
[833267.738278] 		ref#0: tree block backref root 2
[833267.738280] 	item 99 key (1198868168704 169 0) itemoff 12983 itemsize 33
[833267.738281] 		extent refs 1 gen 221219 flags 2
[833267.738282] 		ref#0: tree block backref root 2
[833267.738284] 	item 100 key (1198868185088 169 0) itemoff 12950 itemsize 33
[833267.738285] 		extent refs 1 gen 221219 flags 2
[833267.738286] 		ref#0: tree block backref root 2
[833267.738288] 	item 101 key (1198868201472 169 0) itemoff 12917 itemsize 33
[833267.738289] 		extent refs 1 gen 221219 flags 2
[833267.738290] 		ref#0: tree block backref root 2
[833267.738292] 	item 102 key (1198868217856 169 0) itemoff 12884 itemsize 33
[833267.738293] 		extent refs 1 gen 221219 flags 2
[833267.738294] 		ref#0: tree block backref root 2
[833267.738296] 	item 103 key (1198868234240 169 0) itemoff 12851 itemsize 33
[833267.738298] 		extent refs 1 gen 9305 flags 258
[833267.738298] 		ref#0: shared block backref parent 1182567350272
[833267.738301] 	item 104 key (1198868250624 169 0) itemoff 12818 itemsize 33
[833267.738302] 		extent refs 1 gen 221219 flags 2
[833267.738303] 		ref#0: tree block backref root 2
[833267.738305] 	item 105 key (1198868267008 169 0) itemoff 12785 itemsize 33
[833267.738306] 		extent refs 1 gen 221219 flags 2
[833267.738307] 		ref#0: tree block backref root 2
[833267.738309] 	item 106 key (1198868283392 169 0) itemoff 12752 itemsize 33
[833267.738310] 		extent refs 1 gen 221219 flags 2
[833267.738311] 		ref#0: tree block backref root 2
[833267.738313] 	item 107 key (1198868299776 169 0) itemoff 12719 itemsize 33
[833267.738314] 		extent refs 1 gen 221219 flags 2
[833267.738315] 		ref#0: tree block backref root 2
[833267.738317] 	item 108 key (1198868316160 169 0) itemoff 12686 itemsize 33
[833267.738318] 		extent refs 1 gen 221219 flags 2
[833267.738319] 		ref#0: tree block backref root 2
[833267.738321] 	item 109 key (1198868332544 169 0) itemoff 12653 itemsize 33
[833267.738322] 		extent refs 1 gen 221219 flags 2
[833267.738323] 		ref#0: tree block backref root 2
[833267.738325] 	item 110 key (1198868348928 169 0) itemoff 12620 itemsize 33
[833267.738327] 		extent refs 1 gen 221219 flags 2
[833267.738327] 		ref#0: tree block backref root 2
[833267.738330] 	item 111 key (1198868365312 169 0) itemoff 12587 itemsize 33
[833267.738331] 		extent refs 1 gen 221219 flags 2
[833267.738331] 		ref#0: tree block backref root 2
[833267.738334] 	item 112 key (1198868381696 169 0) itemoff 12554 itemsize 33
[833267.738335] 		extent refs 1 gen 221219 flags 2
[833267.738335] 		ref#0: tree block backref root 2
[833267.738338] 	item 113 key (1198868398080 169 0) itemoff 12521 itemsize 33
[833267.738339] 		extent refs 1 gen 221219 flags 2
[833267.738340] 		ref#0: tree block backref root 2
[833267.738342] 	item 114 key (1198868414464 169 0) itemoff 12488 itemsize 33
[833267.738343] 		extent refs 1 gen 221219 flags 2
[833267.738344] 		ref#0: tree block backref root 2
[833267.738346] 	item 115 key (1198868430848 169 0) itemoff 12455 itemsize 33
[833267.738347] 		extent refs 1 gen 9305 flags 258
[833267.738348] 		ref#0: shared block backref parent 1182567350272
[833267.738350] 	item 116 key (1198868447232 169 0) itemoff 12422 itemsize 33
[833267.738352] 		extent refs 1 gen 221219 flags 2
[833267.738352] 		ref#0: tree block backref root 2
[833267.738355] 	item 117 key (1198868463616 169 0) itemoff 12389 itemsize 33
[833267.738356] 		extent refs 1 gen 221219 flags 2
[833267.738356] 		ref#0: tree block backref root 2
[833267.738359] 	item 118 key (1198868480000 169 0) itemoff 12356 itemsize 33
[833267.738360] 		extent refs 1 gen 221221 flags 2
[833267.738361] 		ref#0: tree block backref root 2
[833267.738363] 	item 119 key (1198868512768 169 0) itemoff 12323 itemsize 33
[833267.738364] 		extent refs 1 gen 221219 flags 2
[833267.738365] 		ref#0: tree block backref root 2
[833267.738367] 	item 120 key (1198868529152 169 0) itemoff 12290 itemsize 33
[833267.738368] 		extent refs 1 gen 221219 flags 2
[833267.738369] 		ref#0: tree block backref root 2
[833267.738371] 	item 121 key (1198868545536 169 0) itemoff 12257 itemsize 33
[833267.738372] 		extent refs 1 gen 221219 flags 2
[833267.738373] 		ref#0: tree block backref root 2
[833267.738375] 	item 122 key (1198868561920 169 0) itemoff 12224 itemsize 33
[833267.738376] 		extent refs 1 gen 9305 flags 258
[833267.738377] 		ref#0: shared block backref parent 1182567350272
[833267.738380] 	item 123 key (1198868578304 169 0) itemoff 12191 itemsize 33
[833267.738381] 		extent refs 1 gen 221219 flags 2
[833267.738381] 		ref#0: tree block backref root 2
[833267.738384] 	item 124 key (1198868594688 169 0) itemoff 12158 itemsize 33
[833267.738385] 		extent refs 1 gen 221219 flags 2
[833267.738386] 		ref#0: tree block backref root 2
[833267.738388] 	item 125 key (1198868611072 169 0) itemoff 12125 itemsize 33
[833267.738389] 		extent refs 1 gen 221219 flags 2
[833267.738390] 		ref#0: tree block backref root 2
[833267.738392] 	item 126 key (1198868627456 169 0) itemoff 12092 itemsize 33
[833267.738393] 		extent refs 1 gen 221287 flags 2
[833267.738394] 		ref#0: tree block backref root 2
[833267.738396] 	item 127 key (1198868643840 169 0) itemoff 12059 itemsize 33
[833267.738397] 		extent refs 1 gen 221219 flags 2
[833267.738398] 		ref#0: tree block backref root 2
[833267.738400] 	item 128 key (1198868660224 169 0) itemoff 12026 itemsize 33
[833267.738401] 		extent refs 1 gen 221279 flags 2
[833267.738402] 		ref#0: tree block backref root 2
[833267.738404] 	item 129 key (1198868692992 169 0) itemoff 11993 itemsize 33
[833267.738406] 		extent refs 1 gen 221221 flags 2
[833267.738406] 		ref#0: tree block backref root 2
[833267.738409] 	item 130 key (1198868758528 169 0) itemoff 11960 itemsize 33
[833267.738410] 		extent refs 1 gen 221219 flags 2
[833267.738410] 		ref#0: tree block backref root 2
[833267.738413] 	item 131 key (1198868774912 169 0) itemoff 11927 itemsize 33
[833267.738414] 		extent refs 1 gen 221219 flags 2
[833267.738415] 		ref#0: tree block backref root 2
[833267.738417] 	item 132 key (1198868791296 169 0) itemoff 11894 itemsize 33
[833267.738418] 		extent refs 1 gen 221219 flags 2
[833267.738419] 		ref#0: tree block backref root 2
[833267.738421] 	item 133 key (1198868824064 169 0) itemoff 11861 itemsize 33
[833267.738422] 		extent refs 1 gen 221219 flags 2
[833267.738423] 		ref#0: tree block backref root 2
[833267.738425] 	item 134 key (1198868840448 169 0) itemoff 11828 itemsize 33
[833267.738426] 		extent refs 1 gen 221219 flags 2
[833267.738427] 		ref#0: tree block backref root 2
[833267.738429] 	item 135 key (1198868856832 169 0) itemoff 11795 itemsize 33
[833267.738430] 		extent refs 1 gen 221288 flags 2
[833267.738431] 		ref#0: tree block backref root 2
[833267.738433] 	item 136 key (1198868873216 169 0) itemoff 11762 itemsize 33
[833267.738434] 		extent refs 1 gen 221221 flags 2
[833267.738435] 		ref#0: tree block backref root 2
[833267.738437] 	item 137 key (1198868905984 169 0) itemoff 11729 itemsize 33
[833267.738439] 		extent refs 1 gen 9305 flags 258
[833267.738439] 		ref#0: shared block backref parent 1182567350272
[833267.738442] 	item 138 key (1198868955136 169 0) itemoff 11696 itemsize 33
[833267.738443] 		extent refs 1 gen 221288 flags 2
[833267.738444] 		ref#0: tree block backref root 2
[833267.738446] 	item 139 key (1198868971520 169 0) itemoff 11663 itemsize 33
[833267.738447] 		extent refs 1 gen 221221 flags 2
[833267.738448] 		ref#0: tree block backref root 2
[833267.738450] 	item 140 key (1198869037056 169 0) itemoff 11630 itemsize 33
[833267.738451] 		extent refs 1 gen 4894 flags 258
[833267.738452] 		ref#0: shared block backref parent 1197685424128
[833267.738454] 	item 141 key (1198869053440 169 0) itemoff 11597 itemsize 33
[833267.738456] 		extent refs 1 gen 4894 flags 258
[833267.738456] 		ref#0: shared block backref parent 1201960845312
[833267.738459] 	item 142 key (1198869069824 169 0) itemoff 11564 itemsize 33
[833267.738460] 		extent refs 1 gen 221221 flags 2
[833267.738461] 		ref#0: tree block backref root 2
[833267.738463] 	item 143 key (1198869102592 169 0) itemoff 11531 itemsize 33
[833267.738464] 		extent refs 1 gen 221221 flags 2
[833267.738465] 		ref#0: tree block backref root 2
[833267.738467] 	item 144 key (1198869135360 169 0) itemoff 11498 itemsize 33
[833267.738468] 		extent refs 1 gen 221219 flags 2
[833267.738469] 		ref#0: tree block backref root 2
[833267.738471] 	item 145 key (1198869151744 169 0) itemoff 11465 itemsize 33
[833267.738472] 		extent refs 1 gen 221219 flags 2
[833267.738473] 		ref#0: tree block backref root 2
[833267.738475] 	item 146 key (1198869184512 169 0) itemoff 11432 itemsize 33
[833267.738476] 		extent refs 1 gen 221219 flags 2
[833267.738477] 		ref#0: tree block backref root 2
[833267.738479] 	item 147 key (1198869217280 169 0) itemoff 11399 itemsize 33
[833267.738481] 		extent refs 1 gen 221221 flags 2
[833267.738481] 		ref#0: tree block backref root 2
[833267.738484] 	item 148 key (1198869233664 169 0) itemoff 11366 itemsize 33
[833267.738485] 		extent refs 1 gen 4894 flags 258
[833267.738485] 		ref#0: shared block backref parent 1198871592960
[833267.738488] 	item 149 key (1198869250048 169 0) itemoff 11333 itemsize 33
[833267.738489] 		extent refs 1 gen 221221 flags 2
[833267.738490] 		ref#0: tree block backref root 2
[833267.738492] 	item 150 key (1198869299200 169 0) itemoff 11300 itemsize 33
[833267.738493] 		extent refs 1 gen 221219 flags 2
[833267.738494] 		ref#0: tree block backref root 2
[833267.738496] 	item 151 key (1198869315584 169 0) itemoff 11267 itemsize 33
[833267.738497] 		extent refs 1 gen 221288 flags 2
[833267.738498] 		ref#0: tree block backref root 2
[833267.738500] 	item 152 key (1198869331968 169 0) itemoff 11234 itemsize 33
[833267.738502] 		extent refs 1 gen 221221 flags 2
[833267.738502] 		ref#0: tree block backref root 2
[833267.738504] 	item 153 key (1198869348352 169 0) itemoff 11201 itemsize 33
[833267.738506] 		extent refs 1 gen 221219 flags 2
[833267.738506] 		ref#0: tree block backref root 2
[833267.738509] 	item 154 key (1198869381120 169 0) itemoff 11168 itemsize 33
[833267.738510] 		extent refs 1 gen 4894 flags 258
[833267.738510] 		ref#0: shared block backref parent 1197685424128
[833267.738513] 	item 155 key (1198869413888 169 0) itemoff 11135 itemsize 33
[833267.738514] 		extent refs 1 gen 221289 flags 2
[833267.738515] 		ref#0: tree block backref root 2
[833267.738517] 	item 156 key (1198869430272 169 0) itemoff 11102 itemsize 33
[833267.738518] 		extent refs 1 gen 221219 flags 2
[833267.738519] 		ref#0: tree block backref root 2
[833267.738521] 	item 157 key (1198869446656 169 0) itemoff 11069 itemsize 33
[833267.738522] 		extent refs 1 gen 221219 flags 2
[833267.738523] 		ref#0: tree block backref root 2
[833267.738525] 	item 158 key (1198869463040 169 0) itemoff 11036 itemsize 33
[833267.738526] 		extent refs 1 gen 221219 flags 2
[833267.738527] 		ref#0: tree block backref root 2
[833267.738529] 	item 159 key (1198869544960 169 0) itemoff 11003 itemsize 33
[833267.738531] 		extent refs 1 gen 221219 flags 2
[833267.738531] 		ref#0: tree block backref root 2
[833267.738534] 	item 160 key (1198869577728 169 0) itemoff 10970 itemsize 33
[833267.738535] 		extent refs 1 gen 221219 flags 2
[833267.738535] 		ref#0: tree block backref root 2
[833267.738538] 	item 161 key (1198869594112 169 0) itemoff 10937 itemsize 33
[833267.738539] 		extent refs 1 gen 221221 flags 2
[833267.738540] 		ref#0: tree block backref root 2
[833267.738542] 	item 162 key (1198869610496 169 0) itemoff 10904 itemsize 33
[833267.738543] 		extent refs 1 gen 221221 flags 2
[833267.738544] 		ref#0: tree block backref root 2
[833267.738546] 	item 163 key (1198869626880 169 0) itemoff 10871 itemsize 33
[833267.738547] 		extent refs 1 gen 221221 flags 2
[833267.738548] 		ref#0: tree block backref root 2
[833267.738550] 	item 164 key (1198869643264 169 0) itemoff 10838 itemsize 33
[833267.738551] 		extent refs 1 gen 221221 flags 2
[833267.738552] 		ref#0: tree block backref root 2
[833267.738554] 	item 165 key (1198869659648 169 0) itemoff 10805 itemsize 33
[833267.738555] 		extent refs 1 gen 221221 flags 2
[833267.738556] 		ref#0: tree block backref root 2
[833267.738558] 	item 166 key (1198869741568 169 0) itemoff 10772 itemsize 33
[833267.738559] 		extent refs 1 gen 221289 flags 2
[833267.738560] 		ref#0: tree block backref root 2
[833267.738562] 	item 167 key (1198869790720 169 0) itemoff 10739 itemsize 33
[833267.738563] 		extent refs 1 gen 221219 flags 2
[833267.738564] 		ref#0: tree block backref root 2
[833267.738566] 	item 168 key (1198869823488 169 0) itemoff 10706 itemsize 33
[833267.738567] 		extent refs 1 gen 221219 flags 2
[833267.738568] 		ref#0: tree block backref root 2
[833267.738570] 	item 169 key (1198869839872 169 0) itemoff 10673 itemsize 33
[833267.738572] 		extent refs 1 gen 221221 flags 2
[833267.738572] 		ref#0: tree block backref root 2
[833267.738574] 	item 170 key (1198869856256 169 0) itemoff 10640 itemsize 33
[833267.738576] 		extent refs 1 gen 221221 flags 2
[833267.738576] 		ref#0: tree block backref root 2
[833267.738579] 	item 171 key (1198869889024 169 0) itemoff 10607 itemsize 33
[833267.738580] 		extent refs 1 gen 221221 flags 2
[833267.738580] 		ref#0: tree block backref root 2
[833267.738583] 	item 172 key (1198869905408 169 0) itemoff 10574 itemsize 33
[833267.738584] 		extent refs 1 gen 221221 flags 2
[833267.738584] 		ref#0: tree block backref root 2
[833267.738587] 	item 173 key (1198869921792 169 0) itemoff 10541 itemsize 33
[833267.738588] 		extent refs 1 gen 221221 flags 2
[833267.738588] 		ref#0: tree block backref root 2
[833267.738591] 	item 174 key (1198869938176 169 0) itemoff 10508 itemsize 33
[833267.738592] 		extent refs 1 gen 221219 flags 2
[833267.738593] 		ref#0: tree block backref root 2
[833267.738595] 	item 175 key (1198869970944 169 0) itemoff 10475 itemsize 33
[833267.738596] 		extent refs 1 gen 221221 flags 2
[833267.738597] 		ref#0: tree block backref root 2
[833267.738599] 	item 176 key (1198870003712 169 0) itemoff 10442 itemsize 33
[833267.738600] 		extent refs 1 gen 221221 flags 2
[833267.738601] 		ref#0: tree block backref root 2
[833267.738603] 	item 177 key (1198870036480 169 0) itemoff 10409 itemsize 33
[833267.738604] 		extent refs 1 gen 221219 flags 2
[833267.738605] 		ref#0: tree block backref root 2
[833267.738607] 	item 178 key (1198870052864 169 0) itemoff 10376 itemsize 33
[833267.738608] 		extent refs 1 gen 221221 flags 2
[833267.738609] 		ref#0: tree block backref root 2
[833267.738611] 	item 179 key (1198870069248 169 0) itemoff 10343 itemsize 33
[833267.738612] 		extent refs 1 gen 221219 flags 2
[833267.738613] 		ref#0: tree block backref root 2
[833267.738615] 	item 180 key (1198870085632 169 0) itemoff 10310 itemsize 33
[833267.738616] 		extent refs 1 gen 221221 flags 2
[833267.738617] 		ref#0: tree block backref root 2
[833267.738619] 	item 181 key (1198870151168 169 0) itemoff 10277 itemsize 33
[833267.738620] 		extent refs 1 gen 221219 flags 2
[833267.738621] 		ref#0: tree block backref root 2
[833267.738623] 	item 182 key (1198870413312 169 0) itemoff 10244 itemsize 33
[833267.738625] 		extent refs 1 gen 221219 flags 2
[833267.738625] 		ref#0: tree block backref root 2
[833267.738627] 	item 183 key (1198870429696 169 0) itemoff 10211 itemsize 33
[833267.738629] 		extent refs 1 gen 221219 flags 2
[833267.738629] 		ref#0: tree block backref root 2
[833267.738631] 	item 184 key (1198870446080 169 0) itemoff 10178 itemsize 33
[833267.738633] 		extent refs 1 gen 221219 flags 2
[833267.738633] 		ref#0: tree block backref root 2
[833267.738636] 	item 185 key (1198870462464 169 0) itemoff 10145 itemsize 33
[833267.738637] 		extent refs 1 gen 221219 flags 2
[833267.738637] 		ref#0: tree block backref root 2
[833267.738640] 	item 186 key (1198870478848 169 0) itemoff 10112 itemsize 33
[833267.738641] 		extent refs 1 gen 221219 flags 2
[833267.738641] 		ref#0: tree block backref root 2
[833267.738644] 	item 187 key (1198870495232 169 0) itemoff 10079 itemsize 33
[833267.738645] 		extent refs 1 gen 221219 flags 2
[833267.738646] 		ref#0: tree block backref root 2
[833267.738648] 	item 188 key (1198870544384 169 0) itemoff 10046 itemsize 33
[833267.738649] 		extent refs 1 gen 221219 flags 2
[833267.738650] 		ref#0: tree block backref root 2
[833267.738652] 	item 189 key (1198870626304 169 0) itemoff 10013 itemsize 33
[833267.738653] 		extent refs 1 gen 221221 flags 2
[833267.738654] 		ref#0: tree block backref root 2
[833267.738656] 	item 190 key (1198870642688 169 0) itemoff 9980 itemsize 33
[833267.738657] 		extent refs 1 gen 221221 flags 2
[833267.738658] 		ref#0: tree block backref root 2
[833267.738660] 	item 191 key (1198870659072 169 0) itemoff 9947 itemsize 33
[833267.738661] 		extent refs 1 gen 221219 flags 2
[833267.738662] 		ref#0: tree block backref root 2
[833267.738664] 	item 192 key (1198870691840 169 0) itemoff 9914 itemsize 33
[833267.738665] 		extent refs 1 gen 221219 flags 2
[833267.738666] 		ref#0: tree block backref root 2
[833267.738668] 	item 193 key (1198870839296 169 0) itemoff 9881 itemsize 33
[833267.738669] 		extent refs 1 gen 221221 flags 2
[833267.738670] 		ref#0: tree block backref root 2
[833267.738672] 	item 194 key (1198870855680 169 0) itemoff 9848 itemsize 33
[833267.738673] 		extent refs 1 gen 221221 flags 2
[833267.738674] 		ref#0: tree block backref root 2
[833267.738676] 	item 195 key (1198870872064 169 0) itemoff 9815 itemsize 33
[833267.738677] 		extent refs 1 gen 221221 flags 2
[833267.738678] 		ref#0: tree block backref root 2
[833267.738680] 	item 196 key (1198870904832 169 0) itemoff 9782 itemsize 33
[833267.738681] 		extent refs 1 gen 221219 flags 2
[833267.738682] 		ref#0: tree block backref root 2
[833267.738684] 	item 197 key (1198870937600 169 0) itemoff 9749 itemsize 33
[833267.738685] 		extent refs 1 gen 221219 flags 2
[833267.738686] 		ref#0: tree block backref root 2
[833267.738688] 	item 198 key (1198870953984 169 0) itemoff 9716 itemsize 33
[833267.738689] 		extent refs 1 gen 221221 flags 2
[833267.738690] 		ref#0: tree block backref root 2
[833267.738692] 	item 199 key (1198870970368 169 0) itemoff 9683 itemsize 33
[833267.738693] 		extent refs 1 gen 221219 flags 2
[833267.738694] 		ref#0: tree block backref root 2
[833267.738696] 	item 200 key (1198870986752 169 0) itemoff 9650 itemsize 33
[833267.738698] 		extent refs 1 gen 221221 flags 2
[833267.738698] 		ref#0: tree block backref root 2
[833267.738700] 	item 201 key (1198871019520 169 0) itemoff 9617 itemsize 33
[833267.738702] 		extent refs 1 gen 4894 flags 258
[833267.738702] 		ref#0: shared block backref parent 1198871592960
[833267.738705] 	item 202 key (1198871035904 169 0) itemoff 9584 itemsize 33
[833267.738706] 		extent refs 1 gen 221219 flags 2
[833267.738707] 		ref#0: tree block backref root 2
[833267.738709] BTRFS error (device sda1): unable to find ref byte nr 1198869807104 parent 0 root 2  owner 0 offset 0
[833267.738753] ------------[ cut here ]------------
[833267.738754] BTRFS: Transaction aborted (error -2)
[833267.738780] WARNING: CPU: 1 PID: 27878 at fs/btrfs/extent-tree.c:6801 __btrfs_free_extent+0x70f/0x940 [btrfs]
[833267.738781] Modules linked in: soundcore dm_mod nouveau kvm_intel mxm_wmi wmi video kvm ttm drm_kms_helper drm sg evdev serio_raw i2c_algo_bit iTCO_wdt iTCO_vendor_support pcspkr irqbypass pcc_cpufreq acpi_cpufreq button coretemp loop ip_tables x_tables autofs4 reiserfs btrfs zstd_decompress zstd_compress xxhash raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c crc32c_generic raid1 raid0 multipath linear md_mod sd_mod ata_generic ahci pata_jmicron ata_piix libahci ehci_pci uhci_hcd ehci_hcd i2c_i801 libata lpc_ich r8169 realtek libphy scsi_mod usbcore usb_common
[833267.738819] CPU: 1 PID: 27878 Comm: btrfs-transacti Tainted: G        W         4.19.0-5-686-pae #1 Debian 4.19.37-5+deb10u2
[833267.738820] Hardware name: Gigabyte Technology Co., Ltd. P35T-DQ6/P35T-DQ6, BIOS F5 02/27/2008
[833267.738837] EIP: __btrfs_free_extent+0x70f/0x940 [btrfs]
[833267.738839] Code: 00 8b 45 a4 8b 40 3c f0 0f ba a8 54 07 00 00 02 0f 92 c0 83 c4 30 84 c0 0f 85 19 d7 09 00 6a fe 68 e8 2f fd f7 e8 35 a9 14 d4 <0f> 0b 5b 5e e9 04 d7 09 00 83 e8 01 8d 55 df 89 47 20 8d 04 80 6a
[833267.738840] EAX: 00000025 EBX: 00000000 ECX: f6fb056c EDX: 00000007
[833267.738841] ESI: 22358000 EDI: dbaa11e0 EBP: dcaa5e08 ESP: dcaa5d80
[833267.738843] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010296
[833267.738844] CR0: 80050033 CR2: 0058f054 CR3: 24e30000 CR4: 000006f0
[833267.738845] Call Trace:
[833267.738848]  ? discard_slab+0x2c/0x40
[833267.738866]  __btrfs_run_delayed_refs+0x20d/0x1030 [btrfs]
[833267.738869]  ? kmem_cache_free+0x172/0x190
[833267.738883]  ? btrfs_free_path.part.28+0x1c/0x20 [btrfs]
[833267.738897]  ? btrfs_free_path.part.28+0x1c/0x20 [btrfs]
[833267.738914]  btrfs_run_delayed_refs+0x6f/0x150 [btrfs]
[833267.738933]  btrfs_commit_transaction+0x270/0x970 [btrfs]
[833267.738952]  ? start_transaction+0x81/0x420 [btrfs]
[833267.738955]  ? __next_timer_interrupt+0xc0/0xc0
[833267.738973]  transaction_kthread+0x175/0x1b0 [btrfs]
[833267.738976]  kthread+0xf0/0x110
[833267.738994]  ? btrfs_cleanup_transaction+0x4c0/0x4c0 [btrfs]
[833267.738995]  ? kthread_associate_blkcg+0xa0/0xa0
[833267.738998]  ret_from_fork+0x2e/0x38
[833267.739000] ---[ end trace 2b4d9362179b4180 ]---
[833267.739019] BTRFS: error (device sda1) in __btrfs_free_extent:6801: errno=-2 No such entry
[833267.739063] BTRFS info (device sda1): forced readonly
[833267.739068] BTRFS: error (device sda1) in btrfs_run_delayed_refs:2935: errno=-2 No such entry
[833267.739112] BTRFS warning (device sda1): Skipping commit of aborted transaction.
[833267.739116] BTRFS: error (device sda1) in cleanup_transaction:1846: errno=-2 No such entry




I don't know if it is a bug or it is my btrfs partition spoiled somehow.

Another test with "--repair" make BUG_ON:



time btrfs check --mode=lowmem --progress --repair /dev/sda1
enabling repair mode
WARNING: low-memory mode repair support is only partial
Opening filesystem to check...
Checking filesystem on /dev/sda1
UUID: 666a7089-d716-44ff-8081-56b969b58eff
[1/7] checking root items                      (0:04:08 elapsed,
10279825 items checked)
Fixed 0 roots.
ERROR: extent[1198869807104 16384] backref lost (owner: 2, level: 0)
root 2s checked)
ERROR: fail to allocate new chunk No space left on device
Try to exclude all metadata blcoks and extents, it may be slowd, 81140
items checked)
Added an extent item [1198869807104 16384]     (2:16:04 elapsed, 81140
items checked)
Added one tree block ref start 1198869807104 root 26:05 elapsed, 81140
items checked)
ERROR: extent[81379328 16384] backref lost (owner: 2, level: 0) root 2
items checked)
Added an extent item [81379328 16384]
transaction.c:168: btrfs_commit_transaction: BUG_ON `ret` triggered,
value -17
btrfs(+0x3c0ad)[0x5320ad]
btrfs(btrfs_commit_transaction+0x68)[0x5324bb]
btrfs(+0x78c24)[0x56ec24]
btrfs(check_chunks_and_extents_lowmem+0x198)[0x572060]
btrfs(cmd_check+0x16e2)[0x554da5]
btrfs(main+0x22c)[0x502edc]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf1)[0xb7badb41]
btrfs(_start+0x31)[0x502f21]
Przerwane

real    140m42,553s
user    6m14,394s
sys     2m21,156s

Hi Leszek,

Sorry it took me so long to follow-up on this bug.

Leszek Dubiel <leszek.dubiel@dubielvitrum.pl> writes:

For i386 (i686), maybe!  If I remember correctly there are still 32bit
bugs.  Amd64/intel64 has been good since linux-4.4, and I have two
heavily used systems that have been fine since then.  But before for
that?  Ouf...

Leszek Dubiel <leszek.dubiel@dubielvitrum.pl> writes:

Do you remember if you ever balanced metadata?

I guess the upside is it failed faster this time?  (2h20min vs 3days)

The lowmem mode was practically brand new back then, and I wonder how
useful it is to keep this bug open.  Do you remember if you contacted
upstream linux-btrfs?  Often they'll expand he scope of btrfs-check to
accommodate new cases.

Cheers!
Nicholas

Please close the bug.

I don't see it anymore,
and maybe it was fixed here:

https://github.com/kdave/btrfs-progs/issues/225








W dniu 12.10.2025 o 03:41, Nicholas D Steeves pisze: