This partly reverts 8f0807023d067e2bb585a2ae8da93e59689d10f1, bringing
back the umount(/sys) attempt.
In a LXC container we're unable to umount the sysfs instance, nor mount
a read-write one. We still are able to create a new read-only instance.
Nevertheless, it still makes sense to attempt the umount() even though
the sysfs is mounted read-only. Otherwise we may end up attempting to
mount a sysfs with the same flags as is already mounted, resulting in
an EBUSY error (meaning "Already mounted").
Perhaps this is not a very likely scenario in real world, but we hit
it in NetworkManager test suite and makes netns_switch() somewhat more
robust. It also fixes the case, when /sys wasn't mounted at all.
Signed-off-by: Lubomir Rintel <lkund...@v3.sk>
---
lib/namespace.c | 20 +++++++-------------
1 file changed, 7 insertions(+), 13 deletions(-)
diff --git a/lib/namespace.c b/lib/namespace.c
index 43e0fe34..06ae0a48 100644
--- a/lib/namespace.c
+++ b/lib/namespace.c
@@ -82,19 +82,13 @@ int netns_switch(char *name)
/* Mount a version of /sys that describes the network namespace */
- if (statvfs("/sys", &fsstat) < 0) {
- fprintf(stderr, "could not stat /sys (not mounted?):
%s\n",strerror(errno));
- return -1;
- }
- if (fsstat.f_flag & ST_RDONLY) {
- /* If /sys is not writable (e.g. in a container), we can't
- * unmount the old /sys instance, but we can still mount a new
- * read-only instance over it. */
- mountflags = MS_RDONLY;
- } else {
- if (umount2("/sys", MNT_DETACH) < 0) {
- fprintf(stderr, "umount of /sys failed: %s\n",
strerror(errno));
- return -1;
+ if (umount2("/sys", MNT_DETACH) < 0) {
+ /* If this fails, perhaps there wasn't a sysfs instance
mounted. Good. */
+ if (statvfs("/sys", &fsstat) == 0) {
+ /* We couldn't umount the sysfs, we'll attempt to
overlay it.
+ * A read-only instance can't be shadowed with a
read-write one. */
+ if (fsstat.f_flag & ST_RDONLY)
+ mountflags = MS_RDONLY;
}
}
if (mount(name, "/sys", "sysfs", mountflags, NULL) < 0) {
--
2.17.1
