To fill in some gaps, I've had to make some assumptions:
* trivial changes (such as checking for an additional function or
header file in libglnx.m4) are assumed to not be copyrightable
* Will Thompson and Matthew Leeds are assumed to be contributing on
behalf of Endless Mobile Inc.
* files with no explicit licensing information are assumed to be
under the license found in COPYING
Reference: https://reuse.software/
Signed-off-by: Simon McVittie <smcv@debian.org>
This doesn't exist on some very old platforms. In the original file
in systemd, it was here for char32_t and char16_t, which we don't use.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Planning to use memfd_create() in flatpak and rpm-ostree, which both use
bubblewrap, and want to pass read-only data via file descriptor to the
container. Passing via `O_TMPFILE` requires `O_RDWR` (read and write),
and passing via a pipe would require buffering.
The systemd `missing.h` has grown enormously; I only cherry-picked the bits for
memfd.
I want the `RENAME_EXCHANGE` version for rpm-ostree, to atomically
swap `/usr/share/rpm` (a directory) with a new verison. While
we're here we might as well expose `RENAME_NOREPLACE` in case
something else wants it.
These both have fallbacks to the non-atomic version.
Closes: https://github.com/GNOME/libglnx/pull/36
We had a bug previously where we failed to clean up a temporary file
in an error path. This is a classic case where the new `O_TMPFILE`
API in Linux is nicer.
To implement this, as usual we start with some original bits from
systemd. But in this case I ended up having to heavily modify it
because systemd doesn't support "link into place and overwrite". They
don't actually use their tempfile code much at all in fact - as far as
I can tell, just in the coredump code.
Whereas in many apps, ostree included, a very common use case is
atomically updating an existing file, which is
`glnx_file_replace_contents_at()`, including subtleties like doing an
`fdatasync()` if the file already existed.
Implementing this then is slightly weird since we need to link() the
file into place, then rename() after.
It's still better though because if we e.g. hit `ENOSPC` halfway
through, we'll clean up the file automatically.
We still do keep the mode where we error out if the file exists.
Finally, the ostree core though does have a more unusual case where we
want to ignore EEXIST (allow concurrent object writers), so add
support for that now.
Note: One really confusing bug I had here was that `O_TMPFILE` ignores
the provided mode, and this caused ostree to write refs that weren't
world readable.
Rework things so we always call `fchmod()`, but as a consequence we're
no longer honoring umask in the default case. I doubt anyone will
care, and if they do we should probably fix ostree to consistently use
a mode inherited from the repo or something.
