[CRIU] [PATCH] cgroup: Fix early update of @dir_name in rewrite_cgsets

[Tycho Andersen]

On Wed, May 18, 2016 at 03:32:33PM +0300, Cyrill Gorcunov wrote:
> When we're walking over controllers and their directories
> we should update the directory at the very end because
> otherwise we will not match the rest of them once variable
> is updated.
> 
> So I desided to simply rewrite the helper. Hopefully it
> is more clear now.
> 
> Signed-off-by: Cyrill Gorcunov <gorcunov at virtuozzo.com>

Acked-by: Tycho Andersen <tycho.andersen at canonical.com>

Thanks, Cyrill.

> ---
>  criu/cgroup.c | 109 ++++++++++++++++++++++++++++++++++------------------------
>  1 file changed, 65 insertions(+), 44 deletions(-)
> 
> diff --git a/criu/cgroup.c b/criu/cgroup.c
> index e1d5023..836ac2d 100644
> --- a/criu/cgroup.c
> +++ b/criu/cgroup.c
> @@ -1583,67 +1583,88 @@ err:
>  }
>  
>  static int rewrite_cgsets(CgroupEntry *cge, char **controllers, int n_controllers,
> -			  char **from, char *to)
> +			  char **dir_name, char *newroot)
>  {
> -	int i, j;
> -	bool set_from = false;
> +	size_t dirlen = strlen(*dir_name);
> +	char *dir = *dir_name;
> +	char *dirnew = NULL;
> +	size_t i, j;
> +
> +	/*
> +	 * For example we may have the following in the image:
> +	 *
> +	 * set
> +	 * 	name "hugetlb"
> +	 * 	path "/300"
> +	 *
> +	 * controller
> +	 * 	cnames hugetlb
> +	 * 	dirs
> +	 * 		dirname "300"
> +	 * 		properties ...
> +	 *
> +	 * when we're switching to a new root we need to change
> +	 * @path and don't forget to update the @dirname into
> +	 * new state.
> +	 */
>  
>  	for (i = 0; i < cge->n_sets; i++) {
>  		CgSetEntry *set = cge->sets[i];
> +
>  		for (j = 0; j < set->n_ctls; j++) {
>  			CgMemberEntry *cg = set->ctls[j];
> -			char *tmp = cg->path, *tmp2 = NULL;
>  
> +			/*
> +			 * Make sure if it's same controller
> +			 * and its path with stripping leading
> +			 * "/" is matching to be renamed.
> +			 */
>  			if (!(cgroup_contains(controllers, n_controllers, cg->name) &&
> -					/* +1 to get rid of leading / */
> -					strstartswith(cg->path + 1, *from)))
> +			      strstartswith(cg->path + 1, dir)))
>  				continue;
>  
> -			/* If this cgset has a cgns prefix, let's use
> -			 * that as the start of the root replacement.
> -			 */
>  			if (cg->has_cgns_prefix && cg->cgns_prefix) {
> -				/* Rewrite the group dir to match the
> -				 * prefix. We can do this exactly once
> -				 * since we know all the tasks are in
> -				 * the same cgroup ns (and thus have
> -				 * the same per-controller prefix path)
> -				 * since we don't support nesting.
> -				 */
> -				if (!set_from) {
> -					set_from = true;
> -					tmp2 = *from;
> -					/* -1 because cgns_prefix includes leading / */
> -					*from = xsprintf("%s%s", to, (*from) + cg->cgns_prefix - 1);
> -				}
> +				char *prev = cg->path;
>  
> -				cg->path = xsprintf("%s%s", to, cg->path +
> -							cg->cgns_prefix);
> -				cg->cgns_prefix = strlen(to);
> +				cg->path = xsprintf("%s%s", newroot, cg->path + cg->cgns_prefix);
> +				if (!cg->path) {
> +					cg->path = prev;
> +					return -ENOMEM;
> +				}
> +				xfree(prev);
> +				cg->cgns_prefix = strlen(newroot);
> +
> +				if (!dirnew) {
> +					/* -1 because cgns_prefix includes leading "/" */
> +					dirnew = xsprintf("%s%s", newroot, dir + cg->cgns_prefix - 1);
> +					if (!dirnew)
> +						return -ENOMEM;
> +				}
>  			} else {
> -				/* otherwise, use the old rewriting strategy */
> -				cg->path = xsprintf("%s%s", to, cg->path +
> -							strlen(*from) + 1);
> -				if (!set_from) {
> -					set_from = true;
> -					tmp2 = *from;
> -					*from = xstrdup(to);
> +				char *prev = cg->path;
> +				/*
> +				 * If no prefix present simply rename the
> +				 * root but make sure the rest of path is
> +				 * untouched.
> +				 */
> +				cg->path = xsprintf("%s%s", newroot,
> +						    cg->path + dirlen + 1);
> +				if (!cg->path) {
> +					cg->path = prev;
> +					return -ENOMEM;
> +				}
> +				xfree(prev);
> +				if (!dirnew) {
> +					dirnew = xstrdup(newroot);
> +					if (!dirnew)
> +						return -ENOMEM;
>  				}
>  			}
> -
> -			if (tmp2) {
> -				xfree(tmp2);
> -				if (!*from)
> -					return -1;
> -			}
> -
> -			if (!cg->path)
> -				return -1;
> -
> -			free(tmp);
>  		}
> -
>  	}
> +
> +	xfree(dir);
> +	*dir_name = dirnew;
>  	return 0;
>  }
>  
> -- 
> 2.5.5
>