Merge branch 'baserock/richardmaw/parallelism-improvements'

This stripped out the commit from the patch series on the mailing list
to remove /dev/shm.

Reviewed-by: Sam Thursfield
Reviewed-by: Daniel Silverstone

1 files changed, 5 insertions, 1 deletions

diff --git a/morphlib/extensions.py b/morphlib/extensions.py
index af6ba279..6b81e116 100644
--- a/morphlib/extensions.py
+++ b/morphlib/extensions.py
@@ -223,7 +223,11 @@ class ExtensionSubprocess(object):
             def close_read_end():
                 os.close(log_read_fd)
             p = subprocess.Popen(
-                [filename] + args, cwd=cwd, env=new_env,
+                # We unshare and mount --make-rprivate so mounts done by write
+                # extensions can't interfere with the rest of the system.
+                ['unshare', '-m', '--', '/bin/sh', '-c',
+                 'mount --make-rprivate / && exec "$@"', '-', filename] + args,
+                cwd=cwd, env=new_env,
                 stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                 preexec_fn=close_read_end)
             os.close(log_write_fd)