While the actual commit object format is presently the same, for a
number of reasons we'd like to change it fairly radically. Among
other things, we need to drop our a{sv} types in objects, to protect
against GVariant changing format.
Since now gnome-ostree now longer uses related objects, and nothing
ever used metadata, just drop them both.
If the admin encounters corruption and does:
$ ostree admin fsck --delete
We want them to be able to recover the objects easily from the
network; with this patch, they do:
$ ln -s dummyvalue /ostree/repo/transaction
$ ostree refs --delete remotename:branchname
$ ostree pull remotename
This patch avoids the need for the refs --delete; we might as well
force scan the commit, and with this patch we still print that it
changed.
While the first was useful way back in the day when we were importing
Debian bits and /sbin/init was expecting to find /dev/.initctl as a
named pipe, that's no longer an issue with systemd since it uses
dynamic Unix sockets.
Likewise, character and block devices in /dev are now dynamically
created by the devtmpfs from the kernel.
Less complexity and code here if we just support directories, regular
files, and symbolic links.
If pull is interrupted, we may have downloaded an arbitrary subset of
the requested objects. Previously, we handled this by scanning for
all objects each time.
However, there's an easy optimization - this patch creates a lock file
in the repo. If we don't see that file when starting a pull, we know
we don't need to stat() every file; presence of a dirtree object for
example implies the existence of everything it references.
Originally, the idea was that clients would replicate "OS/tree"s from
a build server, but we'd run things like "ldconfig" on the client.
This was to allow adding e.g. the nVidia binary driver.
However, the triggers were the only thing in the system at the moment
that really had expected knowledge of the *contents* of the OS, like
the location of binaries.
For now, it's architecturally cleaner if we move the burden of
triggers to the tree builder (e.g. gnome-ostree or RPM). Eventually
we may want OSTree to assist with this type of thing (perhaps
something like RPM %ghost), but this is the right thing to do now.
When multiple threads need to uncompress an object, there was
a race condition where thread A could get EEXIST, unlink,
then thread B calls linkat(), then thread A tries to link() but
fails.
We can just loop in this case.
Previously we'd open(path, O_NOATIME) and do a series of small read()
calls to just parse the header. I think this will trigger kernel readahead
into the compressed portion, but we don't care about that.
This should be more efficient.
This seems to work around a likely Linux kernel VFS bug, where I
randomly see ENOENT on link() when we *definitely* called mkdir() at
an earlier point in time.
Colin Walters