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Run annex.thawcontent-command before deleting an object file

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In case annex.freezecontent-command did something that would prevent
deletion.

Sponsored-by: Dartmouth College's Datalad project
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Joey Hess 2022-02-24 14:10:53 -04:00
parent 346007a915
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[[!comment format=mdwn
username="joey"
subject="""comment 6"""
date="2022-02-24T17:30:07Z"
content="""
I've added --debug output for both freezing and thawing.
The behavior will vary between v8 and v10 because of changes to locking; in v8
it has to thaw the content file before it can lock it, and then it will freeze
it back after locking and before removing it.
In v8 drop looks like:
[2022-02-24 13:51:01.946411104] (Annex.Perms) thawing content .git/annex/objects/p9/5Q/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63
[2022-02-24 13:51:01.947501102] (Annex.Perms) freezing content .git/annex/objects/p9/5Q/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63
[2022-02-24 13:51:01.966185222] (Annex.Perms) thawing content directory .git/annex/objects/p9/5Q/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63
[2022-02-24 13:51:01.967659691] (Annex.Perms) thawing content ./foo
In v10 drop looks like:
[2022-02-24 13:50:11.863585194] (Annex.Perms) freezing content directory .git/annex/objects/p9/5Q/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63
[2022-02-24 13:50:11.883859034] (Annex.Perms) thawing content directory .git/annex/objects/p9/5Q/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63
[2022-02-24 13:50:11.885644532] (Annex.Perms) thawing content ./foo
[2022-02-24 13:50:11.887090539] (Annex.Perms) thawing content directory .git/annex/objects/p9/5Q/SHA256E-s30--afdc07f1ee36cca8648193709de3a8bbd7abf1ce9ff23538284d01dee4d9cf63
So that's more or less as I expected (aside from the thawing of the worktree symlink foo
which is kind of weird).
You said "drop freezes thawn key file before thawing key dir" and yes, that's the v8 behavior
shown above.
The reason is safety: If it left the content file thawed after taking the posix
lock of it, but then turned out to be unable to remove it (could not lock
enough other copies of the object in other repos), it would then need to
re-freeze it since it failed to drop it. But waiting until that point to
re-freeze it would leave a perhaps long stretch of time where it was thawed and
vulnerable to being written to. And also if it were interrupted before it could
re-freeze it would leave it thawed until fsck finally noticed and fixed the
problem. So I don't feel what it's doing is wrong with respect to thawing
and then freezing in v8.
Notice that, in v10, it thaws the content directory, but never directly thaws
the content file. So if the content file remaining frozen prevents removing it,
that would also affect v10.
This does complicate freeze hooks that do things that prevent removal
of the file, rather than just preventing write to the file. Of course
those are two different permissions in classical unix permissions, but
not necessarily with your ACLs or with immutability bits etc.
So, I think that what git-annex ought to do is, when there's a thaw
hook, thaw the content file just before unlinking it.
Implemented that. Should solve your second problem.
"""]]