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

Stéphane Graber stgraber at stgraber.org
Tue Jun 11 17:18:30 UTC 2013


On Wed, Jun 05, 2013 at 05:37:03PM -0500, Serge Hallyn wrote:
> 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>

Looks good, for the record I asked for that change as I'm now running
containers on read-only systems where /var/lib/lxc as well as pretty
much everything but /run is read-only.

/run/lock should be pretty standard nowadays, if some distros are still
stuck with /var/lock we can always add some configure magic.

The paths are obviously getting a bit longer, though people aren't really
supposed to directly interact with those locks on the fs, so it shouldn't
matter.

Acked-by: Stéphane Graber <stgraber 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
> 
> 
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