The v10 upgrade should almost be safe now. What remains to be done is
notice when the v10 upgrade has occurred, while holding the shared lock,
and switch to using v10 lock files.
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The upgrade from V9 uses this to avoid an automatic upgrade until 1 year
after the V9 update. It can also be used in future such situations.
Sponsored-by: Dartmouth College's Datalad project
v10 will run 1 year after the upgrade to v9, to give time for any v8
processes to die. Until that point, the v10 upgrade will be tried by
every process but deferred, so added support for deferring upgrades.
The upgrade prevention lock file that will be used by v10 is not yet
implemented, so it does not yet defer.
Sponsored-by: Dartmouth College's Datalad project
Upgrade the shared lock to an exclusive lock, and then delete the
lock file. If there is another process still holding the shared lock,
the first process will fail taking the exclusive lock, and not delete
the lock file; then the other process will later delete it.
Note that, in the time period where the exclusive lock is held, other
attempts to lock the content in place would fail. This is unlikely to be
a problem since it's a short period.
Other attempts to lock the content for removal would also fail in that
time period, but that's no different than a removal failing because
content is locked to prevent removal.
Sponsored-by: Dartmouth College's Datalad project
When dropping content, this was already done after deleting the content
file, but the lock file prevents deleting the directories. So, try the
deletion again.
This does mean there's a small added overhead of a failed rmdir().
Sponsored-by: Dartmouth College's Datalad project
This seems to be the best that can be done to avoid forever accumulating
the new content lock files, while being fully safe.
This is fixing code paths that have lingered unused since direct mode!
And direct mode seems to have been buggy in this area, since the content
lock file was deleted on unlock. But with a shared lock, there could be
another process that also had the lock file locked, and deleting it
invalidates that lock.
So, the lock file cannot be deleted after a shared lock. At least, not
wihout taking an exclusive lock first.. which I have not pursued yet but may.
After an exclusive lock, the lock file can be deleted. But there is
still a potential race, where the exclusive lock is held, and another
process gets the file open, just as the exclusive lock is dropped and
the lock file is deleted. That other process would be left with a file
handle it can take a shared lock of, but with no effect since the file
is deleted. Annex.Transfer also deletes lock files, and deals with this
same problem by using checkSaneLock, which is how I've dealt with it
here.
Sponsored-by: Dartmouth College's Datalad project
Now the content lock files are used in v9. However, I am not yet certian
they are correct. In particular, lockContentUsing deletes
the content lock file on unlock. But what if there's a shared lock
by another process? That seems like it would discard that lock too!
(Windows seems like it would not have the same problem, because as the
comment in there says, "Can't delete a locked file on Windows".
So if another process has a shared lock, removing it presumably fails.)
Sponsored-by: Dartmouth College's Datalad project
Seems to work ok. Unsure yet about the actual locking changes being
correct.
This is not the end of the story with upgrades, because it is unsafe for
this upgrade as implemented to run in a repository where an old
git-annex process is already running. The old process would use the old
locking method, and not notice files locked by the new, and this could
result in data loss. This problem will need to be dealt with before this
branch is suitable for merging.
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Windows has always used a separate lock file, but on unix, the content
file itself was locked, and in v9 that changes to also use a separate
lock file.
This needs to be tested more. Eg, what happens after dropping a file;
does the the content lock file get deleted too, or linger around?
Sponsored-by: Dartmouth College's Datalad project
v9 will not need to write to annex content files in order to lock them,
so freezeContent removes the write bit in a shared repository, the same
as in any other repository.
checkContentWritePerm makes sure that the write perm is not set, which
will let git-annex fsck fix up the permissions. Upgrading to v9
will need to fix the permissions as well, but it seems likely there will
be situations where the user git-annex is running an upgrade as cannot,
so it will have to leave the write bit set. In such a case, git-annex
fsck can fix it later.
Sponsored-by: Dartmouth College's Datalad project
This is the start of v9, but it's currently identical to v8, and v8 is
not upgraded to it. git-annex upgrade will upgrade to v9 with this
change.
Sponsored-by: Dartmouth College's Datalad project
Do not populate the keys database with associated files,
because a bare repo has no working tree, and so it does not make sense to
populate it.
Queries of associated files in the keys database always return empty lists
in a bare repo, even if it's somehow populated. One way it could be
populated is if a user converts a non-bare repo to a bare repo.
Note that Git.Config.isBare does a string comparison, so this is not free!
But, that string comparison is very small compared to a sqlite query.
Sponsored-by: Erik Bjäreholt on Patreon
On a phone with Calyxos, adb find in /sdcard complains:
find: ./Android/data/com.android.providers.downloads.ui: Permission denied
But otherwise works, so this option makes import and export work ok, except
for that one app's data.
Sponsored-by: Graham Spencer
