commit: fa82725ba03ffa5edf0b82db7307c87fc97e83f2 Author: Mike Frysinger <vapier <AT> chromium <DOT> org> AuthorDate: Wed Mar 30 06:32:07 2022 +0000 Commit: Sam James <sam <AT> gentoo <DOT> org> CommitDate: Fri Apr 15 02:46:19 2022 +0000 URL: https://gitweb.gentoo.org/proj/portage.git/commit/?id=fa82725b
movefile: merge symlinks atomically Since POSIX allows renaming symlinks with symlinks, use that to get atomic updates. This is faster and less flaky to parallel processes: removing a live symlink and then recreating it leaves a small window where other things might try to use it but fail. [sam: cherry-picked from chromiumos' third_party/portage_tool repo] (cherry picked from commit cherry-pick 80ed2dac95db81acac8043e6685d0a853a08d268) Bug: https://bugs.gentoo.org/836400 Signed-off-by: Sam James <sam <AT> gentoo.org> Closes: https://github.com/gentoo/portage/pull/816 Signed-off-by: Sam James <sam <AT> gentoo.org> lib/portage/util/movefile.py | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/lib/portage/util/movefile.py b/lib/portage/util/movefile.py index ddafe5571..4dc08af26 100644 --- a/lib/portage/util/movefile.py +++ b/lib/portage/util/movefile.py @@ -171,7 +171,7 @@ def movefile( bsd_chflags.chflags(os.path.dirname(dest), 0) if destexists: - if stat.S_ISLNK(dstat[stat.ST_MODE]): + if not stat.S_ISLNK(sstat[stat.ST_MODE]) and stat.S_ISLNK(dstat[stat.ST_MODE]): try: os.unlink(dest) destexists = 0 @@ -185,8 +185,18 @@ def movefile( target = os.readlink(src) if mysettings and "D" in mysettings and target.startswith(mysettings["D"]): target = target[len(mysettings["D"]) - 1 :] - if destexists and not stat.S_ISDIR(dstat[stat.ST_MODE]): - os.unlink(dest) + # Atomically update the path if it exists. + try: + os.rename(src, dest) + return sstat.st_mtime_ns + except OSError: + # If it failed due to cross-link device, fallthru below. + # Clear the target first so we can create it. + try: + os.unlink(dest) + except FileNotFoundError: + pass + try: if selinux_enabled: selinux.symlink(target, dest, src)
