[CRIU] [PATCH 1/2] cg: Make lacking properties during dump non-fatal

[Tycho Andersen]

Hi Pavel,

On Fri, Aug 15, 2014 at 02:45:30PM +0400, Pavel Emelyanov wrote:
> On 08/14/2014 10:39 PM, gbellack at google.com wrote:
> > From: Garrison Bellack <gbellack at google.com>
> > 
> > Because different kernel versions have different cgroup properties, criu
> > shouldn't crash just because the properties statically listed aren't exact.
> > Instead, during dump, ignore properties the kernel doesn't have and continue.
> > 
> > Change-Id: I5a8b93d6a8a3a9664914f10cf8e2110340dd8b31
> > Signed-off-by: Garrison Bellack <gbellack at google.com>
> 
> I'm OK with the patch and plan to merge it in.
> Tycho, Serge, do you have any concerns?

Nope, I just ran it and it worked fine for me.

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

> > ---
> >  cgroup.c | 32 ++++++++++++++++++++------------
> >  1 file changed, 20 insertions(+), 12 deletions(-)
> > 
> > diff --git a/cgroup.c b/cgroup.c
> > index f8dbbde..016ca6c 100644
> > --- a/cgroup.c
> > +++ b/cgroup.c
> > @@ -284,35 +284,30 @@ static int find_dir(const char *path, struct list_head *dirs, struct cgroup_dir
> >   * Currently this function only supports properties that have 1 value, under 100
> >   * chars
> >   */
> > -static int read_cgroup_prop(struct cgroup_prop *property, const char *fpath)
> > +static int read_cgroup_prop(struct cgroup_prop *property, const char *fullpath)
> >  {
> > -	char pbuf[PATH_MAX], buf[100];
> > +	char buf[100];
> >  	FILE *f;
> >  	char *endptr;
> >  
> > -	if (snprintf(pbuf, PATH_MAX, "%s/%s", fpath, property->name) >= PATH_MAX) {
> > -		pr_err("snprintf output was truncated");
> > -		return -1;
> > -	}
> > -
> > -	f = fopen(pbuf, "r");
> > +	f = fopen(fullpath, "r");
> >  	if (!f) {
> > -		pr_err("Failed opening %s\n", pbuf);
> >  		property->value = NULL;
> > +		pr_perror("Failed opening %s\n", fullpath);
> >  		return -1;
> >  	}
> >  
> >  	memset(buf, 0, sizeof(buf));
> >  	if (fread(buf, sizeof(buf), 1, f) != 1) {
> >  		if (!feof(f)) {
> > -			pr_err("Failed scanning %s\n", pbuf);
> > +			pr_err("Failed scanning %s\n", fullpath);
> >  			fclose(f);
> >  			return -1;
> >  		}
> >  	}
> >  
> >  	if (fclose(f) != 0) {
> > -		pr_err("Failed closing %s\n", pbuf);
> > +		pr_err("Failed closing %s\n", fullpath);
> >  		return -1;
> >  	}
> >  
> > @@ -390,6 +385,7 @@ static int add_cgroup_properties(const char *fpath, struct cgroup_dir *ncd,
> >  				 struct cg_controller *controller)
> >  {
> >  	int i, j;
> > +	char buf[PATH_MAX];
> >  	struct cgroup_prop *prop;
> >  
> >  	for (i = 0; i < controller->n_controllers; ++i) {
> > @@ -397,16 +393,28 @@ static int add_cgroup_properties(const char *fpath, struct cgroup_dir *ncd,
> >  		const char **prop_arr = get_known_properties(controller->controllers[i]);
> >  
> >  		for (j = 0; prop_arr != NULL && prop_arr[j] != NULL; ++j) {
> > +			if (snprintf(buf, PATH_MAX, "%s/%s", fpath, prop_arr[j]) >= PATH_MAX) {
> > +				pr_err("snprintf output was truncated");
> > +				return -1;
> > +			}
> > +
> > +			if (access(buf, F_OK) < 0 && errno == ENOENT) {
> > +				pr_info("Couldn't open %s. This cgroup property may not exist on this kernel\n", buf);
> > +				continue;
> > +			}
> > +
> >  			prop = create_cgroup_prop(prop_arr[j]);
> >  			if (!prop) {
> >  				free_all_cgroup_props(ncd);
> >  				return -1;
> >  			}
> > -			if (read_cgroup_prop(prop, fpath) < 0) {
> > +
> > +			if (read_cgroup_prop(prop, buf) < 0) {
> >  				free_cgroup_prop(prop);
> >  				free_all_cgroup_props(ncd);
> >  				return -1;
> >  			}
> > +
> >  			pr_info("Dumping value %s from %s/%s\n", prop->value, fpath, prop->name);
> >  			list_add_tail(&prop->list, &ncd->properties);
> >  			ncd->n_properties++;
> > 
>