Given the situation explained below, it appears I can fix my btrfs send datastream by updating the UUID and CTRANSID of alternate_sv2. Specifically, Command 1 TLV 1 and 2, or Command 2 TLV 1 and 2. The CRC32 would also be updated.
This would make incremental btrfs "send" backups markedly more useful because it allows me to erase intermediate backups after a time. It's trivial to write a program to do this, so I plan to start testing next week unless anyone has concerns. btrfs subvolume snapshot -r real v1 #later... btrfs subvolume snapshot -r real v2 #later... btrfs subvolume snapshot -r real v3 btrfs send -f sv1 v1 btrfs send -f sv2 v2 -p v1 btrfs send -f sv3 v3 -p v2 btrfs subvolume delete v? btrfs receive -vf sv1 . btrfs receive -vf sv2 . btrfs subvolume delete v1 btrfs send -f alternate_sv2 v2 btrfs subvolume delete v? #Scenario 1 should work (and does) btrfs receive -vf sv1 . btrfs receive -vf sv2 . btrfs receive -vf sv3 . #Scenario 2 should work (but doesn't) btrfs receive -vf alternate_sv2 . btrfs receive -vf sv3 . # "ERROR: could not find parent subvolume" To solve the problem, I plan to update the data for TLV ops 1 and 2 in alternate_sv2. Packet: op 2 SNAPSHOT length 46 crc32 36A251CC TLV: op F PATH length 2 "v2" TLV: op 1 UUID length 10 81A4010723F85C4E996371EE73A413AC TLV: op 2 CTRANSID length 8 EB01000000000000 TLV: op 14 CLONE_UUID length 10 FA2E1AEC25CFD540B7CA404D6584F4AA TLV: op 15 CLONE_CTRANSID length 8 EA01000000000000 It also appears possible to combine two data streams without "btrfs receive", but that's more complicated. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
