Re: hierarchical, tree-like structure of snapshots

[Andrei Borzenkov <arvidjaar@gmail.com>]

[-- Attachment #1.1: Type: text/plain, Size: 1841 bytes --]

01.01.2021 00:36, Zygo Blaxell пишет:
...
> 
> Yeah, I only checked that send completed without error and produced a
> smaller stream.
> 
> I just dumped the send metadata stream from the incremental snapshot now,
> and it's more or less garbage at the start:
> 
> 	# btrfs sub create A
> 	# btrfs sub create B
> 	# date > A/date
> 	# date > B/date
> 	# mkdir A/t B/u
> 	# btrfs sub snap -r A A_RO
> 	# btrfs sub snap -r B B_RO
...
> 	# btrfs send A_RO | btrfs receive -v /tmp/test
> 	At subvol A_RO
> 	At subvol A_RO
> 	receiving subvol A_RO uuid=995adde4-00ac-5e49-8c6f-f01743def072, stransid=7329268
> 	write date - offset=0 length=29
> 	BTRFS_IOC_SET_RECEIVED_SUBVOL uuid=995adde4-00ac-5e49-8c6f-f01743def072, stransid=7329268
> 	# btrfs send B_RO -p A_RO | btrfs receive -v /tmp/test
> 	At subvol B_RO
> 	At snapshot B_RO
> 	receiving snapshot B_RO uuid=4aa7db26-b219-694e-9b3c-f8f737a46bdb, ctransid=7329268 parent_uuid=995adde4-00ac-5e49-8c6f-f01743def072, parent_ctransid=7329268
> 	ERROR: link date -> date failed: File exists
> 
> The btrfs_compare_trees function can handle arbitrary tree differences,

I am not sure. It apparently relies on the fact that inodes are ever
monotonically increasing. This is probably true for clones of the same
subvolume (I assume clone inherits highest_objectid) but two subvolumes
created independently have the same range of inode numbers.

Also I am not sure if using later clone as base for difference to
earlier clone will work for the same reason.

> but something happens in one of the support functions and we get a
> bogus link command.  The rest of the stream is OK though:  we fill
> in the contents of B_RO/date, rename A_RO/t to B_RO/u, and update all
> the timestamps.
> 
> Oh well, I didn't say send didn't have any bugs.  ;)
> 


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 195 bytes --]