[lxc-devel] [PATCH RFC] lxclock: move container locks into /run/lock

[Serge Hallyn]

Currently the lxc API mutexes configuration file read/writes with a
lock called $lxcpath/locks/$lxcname.  This fails if the container
is on a rofs.

This patch moves those locks under /run/lock/lxc.

The $lxcpath/$lxcname/partial file is not moved - if you can't
create it, you probably can't create the container either.

Signed-off-by: Serge Hallyn <serge.hallyn at ubuntu.com>
---
 src/lxc/lxclock.c     | 19 +++++++++++++++----
 src/tests/locktests.c |  5 ++++-
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/lxc/lxclock.c b/src/lxc/lxclock.c
index d004cc5..31bedd8 100644
--- a/src/lxc/lxclock.c
+++ b/src/lxc/lxclock.c
@@ -40,12 +40,14 @@ pthread_mutex_t thread_mutex = PTHREAD_MUTEX_INITIALIZER;
 static char *lxclock_name(const char *p, const char *n)
 {
 	int ret;
-	// $lxcpath/locks/$lxcname + '\0'
-	int len = strlen(p) + strlen(n) + strlen("/locks/") + 1;
+	// /run/lock/lxc/$lxcpath/$lxcname + '\0'
+	int len = strlen(p) + strlen(n) + strlen("/run/lock/lxc/") + 2;
 	char *dest = malloc(len);
+	struct stat sb;
+
 	if (!dest)
 		return NULL;
-	ret = snprintf(dest, len, "%s/locks", p);
+	ret = snprintf(dest, len, "/run/lock/lxc/%s", p);
 	if (ret < 0 || ret >= len) {
 		free(dest);
 		return NULL;
@@ -58,7 +60,16 @@ static char *lxclock_name(const char *p, const char *n)
 		return NULL;
 	}
 
-	ret = snprintf(dest, len, "%s/locks/%s", p, n);
+	ret = stat(p, &sb);
+	if (ret == 0) {
+		// best effort.  If this fails, ignore it
+		if (chown(dest, sb.st_uid, sb.st_gid) < 0)
+			ERROR("Failed ot set owner for lockdir %s\n", dest);
+		if (chmod(dest, sb.st_mode) < 0)
+			ERROR("Failed to set mode for lockdir %s\n", dest);
+	}
+
+	ret = snprintf(dest, len, "/run/lock/lxc/%s/%s", p, n);
 	if (ret < 0 || ret >= len) {
 		free(dest);
 		return NULL;
diff --git a/src/tests/locktests.c b/src/tests/locktests.c
index 96df946..360851f 100644
--- a/src/tests/locktests.c
+++ b/src/tests/locktests.c
@@ -121,7 +121,10 @@ int main(int argc, char *argv[])
 		exit(1);
 	}
 	struct stat sb;
-	char *pathname = "/var/lib/lxc/locks/" mycontainername;
+	// we don't create the file until the container is running, so this
+	// bit of the test needs to be changed
+	//char *pathname = "/run/lock/lxc/var/lib/lxc/" mycontainername;
+	char *pathname = "/run/lock/lxc/var/lib/lxc/";
 	ret = stat(pathname, &sb);
 	if (ret != 0) {
 		fprintf(stderr, "%d: filename %s not created\n", __LINE__,
-- 
1.8.1.2