id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	launchpad_bug
2250	"don't re-use metadata from earlier snapshots, in a ""tahoe backup"""	zooko		"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.)"	defect	new	normal	soon	code-frontend-cli	1.10.0		forward-compatibility tahoe-backup metadata