Skip to content
Snippets Groups Projects
  1. May 02, 2019
  2. Oct 01, 2017
    • Colin Walters's avatar
      missing: Sync from latest systemd, add memfd_create() · dd5fd9c1
      Colin Walters authored
      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.
      dd5fd9c1
  3. Mar 02, 2017
  4. Jul 01, 2016
    • Colin Walters's avatar
      fdio: Add open_tmpfile_linkable() and link_tmpfile_at() · 113c770d
      Colin Walters authored
      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.
      113c770d
Loading