Error: [5873390.037413] BTRFS critical (device dm-4): corrupt leaf: root=2 block=354531753984 slot=121, unexpected item end, have 1447 expect 9639 Looks like a random bit flip in memory: 9639 - 0010 0101 1010 0111 1447 - 0000 0101 1010 0111 # btrfs check -p /dev/mapper/pps-backupn_1 Opening filesystem to check... Checking filesystem on /dev/mapper/pps-backupn_1 UUID: 9622e8b4-6380-4757-ae03-4e3b62168592 incorrect offsets 9639 1447 (0:07:52 elapsed, 12273594 items checked) incorrect offsets 9639 1447 (0:07:58 elapsed, 12279056 items checked) incorrect offsets 9639 1447 [1/7] checking root items (0:10:23 elapsed, 16270087 items checked) incorrect offsets 9639 1447 (0:00:18 elapsed, 39094 items checked) bad block 354531753984 [2/7] checking extents (0:00:19 elapsed, 40979 items checked) ERROR: errors found in extent allocation tree or chunk allocation [...] # btrfs inspect-internal dump-tree -b 354531753984 /dev/mapper/pps-backupn_1 btrfs-progs v5.9 incorrect offsets 9639 1447 incorrect offsets 9639 1447 incorrect offsets 9639 1447 leaf 354531753984 items 158 free space 2133 generation 74182 owner EXTENT_TREE leaf 354531753984 flags 0x1(WRITTEN) backref revision 1 fs uuid 9622e8b4-6380-4757-ae03-4e3b62168592 chunk uuid 35ab8a7e-849e-4387-a8ff-a84191bba8d9 [...] item 120 key (2917664673792 EXTENT_ITEM 4096) itemoff 9639 itemsize 50 refs 2 gen 64116 flags DATA shared data backref parent 358418350080 count 1 shared data backref parent 356655628288 count 1 item 121 key (2917664677888 EXTENT_ITEM 36864) itemoff 1410 itemsize 37 refs 14051230837395947552 gen 620757045 flags |FULL_BACKREF item 122 key (2917664714752 EXTENT_ITEM 4096) itemoff 9539 itemsize 63 refs 3 gen 64116 flags DATA shared data backref parent 361864183808 count 1 shared data backref parent 361830400000 count 1 shared data backref parent 361830350848 count 1 [...] # btrfs-map-logical -l 354531753984 /dev/mapper/pps-backupn_1 mirror 1 logical 354531753984 physical 6074220544 device /dev/mapper/pps-backupn_3 mirror 2 logical 354531753984 physical 258440249344 device /dev/mapper/pps-backupn_1 Above info used to create scripts. Devices and physical offsets used in dump.sh and write.sh. Item key (2917664677888) used to find corrupt item in leaf data, and next item offset + size used to correct corrupt item offset in fix.pl. After running dump.sh, fix.pl, and write.sh all fixed :D # btrfs check -p /dev/mapper/pps-backupn_1 Opening filesystem to check... Checking filesystem on /dev/mapper/pps-backupn_1 UUID: 9622e8b4-6380-4757-ae03-4e3b62168592 [1/7] checking root items (0:10:28 elapsed, 16270087 items checked) [2/7] checking extents (0:27:10 elapsed, 813287 items checked) [3/7] checking free space cache (0:07:48 elapsed, 1754 items checked) [4/7] checking fs roots (1:28:16 elapsed, 573180 items checked) [5/7] checking csums (without verifying data) (0:15:26 elapsed, 4761171 items checked) [6/7] checking root refs (0:00:00 elapsed, 124 items checked) [7/7] checking quota groups skipped (not enabled on this FS) found 1875282239488 bytes used, no error found total csum bytes: 1817881768 total tree bytes: 13322780672 total fs tree bytes: 9424371712 total extent tree bytes: 1795293184 btree space waste bytes: 2425667055 file data blocks allocated: 2405556715520 referenced 2849509068800