[CRIU] [PATCH] cgroup: open cgroup mount point

[Andrew Vagin]

Sorry, this doesn't work too

==================================== ERROR ====================================
Test: zdtm/live/static/cwd01, Namespace: 1
Dump log   : /root/criu/test/dump/cwd01/10361/1/dump.log
--------------------------------- grep Error ---------------------------------
(00.063024) Error (pie/util.c:31): Can't remove tmp dir .criu.cgmounts.cU2sCW: -16
(00.063052) Error (cr-dump.c:1601): Dump core (pid: 10361) failed with -1
(00.078414) Error (cr-dump.c:1914): Dumping FAILED.
------------------------------------- END -------------------------------------
================================= ERROR OVER =================================


On Tue, Jul 15, 2014 at 03:19:15PM +0400, Andrew Vagin wrote:
> Otherwise it can disappear in any moment.
> 
> For example the test system executes tests concurrently and sometimes one
> test looks up a mount point, which has been mounted by another test.
> 
> ==================================== ERROR ====================================
> Test: zdtm/live/static/inotify00, Namespace: 1
> Dump log   : /var/lib/jenkins/jobs/CRIU-dump/workspace/test/dump/inotify00/15535/1/dump.log
> --------------------------------- grep Error ---------------------------------
> (00.021951) Error (cgroup.c:409): cg: failed walking /var/lib/jenkins/jobs/CRIU-dump/workspace/test/dump/signalfd00/15538/1/.criu.cgmounts.UGj28v/ for empty cgroups
> (00.021967) Error (cr-dump.c:1601): Dump core (pid: 15535) failed with -1
> (00.025509) Error (cr-dump.c:1914): Dumping FAILED.
> ------------------------------------- END -------------------------------------
> ================================= ERROR OVER =================================
> 
> Reported-by: Jenkins Criuovich
> Cc: Tycho Andersen <tycho.andersen at canonical.com>
> Signed-off-by: Andrew Vagin <avagin at openvz.org>
> ---
>  cgroup.c | 33 ++++++++++++++++++++-------------
>  1 file changed, 20 insertions(+), 13 deletions(-)
> 
> diff --git a/cgroup.c b/cgroup.c
> index 5114935..16abb64 100644
> --- a/cgroup.c
> +++ b/cgroup.c
> @@ -14,6 +14,7 @@
>  #include "proc_parse.h"
>  #include "util.h"
>  #include "fdset.h"
> +#include "util-pie.h"
>  #include "protobuf.h"
>  #include "protobuf/core.pb-c.h"
>  #include "protobuf/cgroup.pb-c.h"
> @@ -168,10 +169,11 @@ int parse_cg_info(void)
>  	return 0;
>  }
>  
> -static int get_cgroup_mount_point(const char *controller, char *path)
> +static int open_cgroup_mount_point(const char *controller)
>  {
>  	struct mount_info *m;
>  	char name[1024];
> +	int fd;
>  
>  	for (m = cg_mntinfo; m != NULL; m = m->next) {
>  		if (strcmp(m->fstype->name, "cgroup") == 0) {
> @@ -199,8 +201,14 @@ static int get_cgroup_mount_point(const char *controller, char *path)
>  
>  			if (strcmp(name, controller) == 0) {
>  				/* skip the leading '.' in mountpoint */
> -				strcpy(path, m->mountpoint + 1);
> -				return 0;
> +
> +				fd = open(m->mountpoint + 1, O_DIRECTORY);
> +				if (fd < 0) {
> +					pr_perror("Unable to open %s", m->mountpoint + 1);
> +					continue;
> +				}
> +
> +				return fd;
>  			}
>  		}
>  	}
> @@ -346,11 +354,11 @@ static int collect_cgroups(struct list_head *ctls)
>  {
>  	struct cg_ctl *cc;
>  	int ret = 0;
> +	int fd = -1;
>  
>  	list_for_each_entry(cc, ctls, l) {
>  		char path[PATH_MAX];
> -		char *name, mount_point[PATH_MAX], prefix[] = ".criu.cgmounts.XXXXXX";
> -		bool temp_mount = false;
> +		char *name, prefix[] = ".criu.cgmounts.XXXXXX";
>  		struct cg_controller *cg;
>  
>  		if (strstartswith(cc->name, "name="))
> @@ -358,13 +366,13 @@ static int collect_cgroups(struct list_head *ctls)
>  		else
>  			name = cc->name;
>  
> -		if (get_cgroup_mount_point(name, mount_point) < 0) {
> +		fd = open_cgroup_mount_point(name);
> +		if (fd < 0) {
>  			/* Someone is trying to dump a process that is in
>  			 * a controller that isn't mounted, so we mount it for
>  			 * them.
>  			 */
>  			char opts[1024];
> -			temp_mount = true;
>  
>  			if (mkdtemp(prefix) == NULL) {
>  				pr_perror("can't make dir for cg mounts\n");
> @@ -382,10 +390,12 @@ static int collect_cgroups(struct list_head *ctls)
>  				return -1;
>  			}
>  
> -			strcpy(mount_point, prefix);
> +			fd = open_detach_mount(prefix);
> +			if (fd < 0)
> +				return -1;
>  		}
>  
> -		snprintf(path, PATH_MAX, "%s/%s", mount_point, cc->path);
> +		snprintf(path, PATH_MAX, "/proc/self/fd/%d/%s", fd, cc->path);
>  
>  		current_controller = NULL;
>  
> @@ -420,10 +430,7 @@ static int collect_cgroups(struct list_head *ctls)
>  		}
>  
>  out:
> -		if (temp_mount) {
> -			umount(prefix);
> -			rmdir(prefix);
> -		}
> +		close_safe(&fd);
>  
>  		if (ret < 0)
>  			return ret;
> -- 
> 1.9.3
>