#2250 new defect

don't re-use metadata from earlier snapshots, in a "tahoe backup"

Reported by: zooko Owned by:
Priority: normal Milestone: soon
Component: code-frontend-cli Version: 1.10.0
Keywords: forward-compatibility tahoe-backup metadata Cc:
Launchpad Bug:


Currently if you run tahoe backup on a directory, and the contents of the children of that directory have not changed, then tahoe backup will reuse the already-created immutable LAFS-directory. Therefore, the metadata on the children, such as the timestamps, owner information, etc., will be re-used. This can lead to a snapshot which says "Here's the state of the directory at time T", and then it shows the children, with their metadata from an earlier snapshot. This is very misleading, and only a very sophisticated user would be able to figure out that the metadata was actually re-used from a previous snapshot, and would be able to figure out in what cases metadata gets re-used vs. gets read afresh from the filesystem.

To fix this, make it so that if any of the metadata of any of the children has changed, then we make a new LAFS-directory to hold the current metadata of all the children, even if the contents of the children (and therefore their immutable file read-caps) haven't changed. (Excluding st_atime, which we do not record anyway, and which would cause intolerable thrashing if we did.)

Change History (7)

comment:1 Changed at 2014-06-27T01:13:50Z by zooko

See related tickets:

  • #897 ("tahoe backup" thinks "ctime" means "creation time")
  • #1946 (consider removing some st_* fields from metadata)

comment:2 Changed at 2014-07-24T00:20:28Z by daira

  • Milestone changed from undecided to 1.12.0


comment:3 Changed at 2014-07-24T00:21:01Z by daira

  • Component changed from code to code-frontend-cli

comment:4 Changed at 2016-03-22T05:02:25Z by warner

  • Milestone changed from 1.12.0 to 1.13.0

Milestone renamed

comment:5 Changed at 2016-06-28T18:17:14Z by warner

  • Milestone changed from 1.13.0 to 1.14.0

renaming milestone

comment:6 Changed at 2020-06-30T14:45:13Z by exarkun

  • Milestone changed from 1.14.0 to 1.15.0

Moving open issues out of closed milestones.

comment:7 Changed at 2021-03-30T18:40:19Z by meejah

  • Milestone changed from 1.15.0 to soon

Ticket retargeted after milestone closed

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