[lxc-devel] [lxc/master] cgfsng: fail when limits fail to apply

[brauner on Github]

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From b3646d7e99abb30c526b1e0be72b7c4a373d3a95 Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner at ubuntu.com>
Date: Tue, 19 Sep 2017 16:24:37 +0200
Subject: [PATCH] cgfsng: fail when limits fail to apply

So far, we silently skipped over limits that failed to be applied which is very
odd. Let's error on when cgroup limits fail to apply.

Closes #1815.

Signed-off-by: Christian Brauner <christian.brauner at ubuntu.com>
---
 src/lxc/cgroups/cgfsng.c | 29 ++++++++++++++++++-----------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index fe3fd7062..ed391a616 100644
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -2009,15 +2009,16 @@ static int convert_devpath(const char *invalue, char *dest)
  */
 static int lxc_cgroup_set_data(const char *filename, const char *value, struct cgfsng_handler_data *d)
 {
-	char *subsystem = NULL, *p;
-	int ret = 0;
-	struct hierarchy *h;
+	char *fullpath, *p;
 	/* "b|c <2^64-1>:<2^64-1> r|w|m" = 47 chars max */
 	char converted_value[50];
+	struct hierarchy *h;
+	int ret = 0;
+	char *controller = NULL;
 
-	subsystem = alloca(strlen(filename) + 1);
-	strcpy(subsystem, filename);
-	if ((p = strchr(subsystem, '.')) != NULL)
+	controller = alloca(strlen(filename) + 1);
+	strcpy(controller, filename);
+	if ((p = strchr(controller, '.')) != NULL)
 		*p = '\0';
 
 	if (strcmp("devices.allow", filename) == 0 && value[0] == '/') {
@@ -2028,12 +2029,18 @@ static int lxc_cgroup_set_data(const char *filename, const char *value, struct c
 
 	}
 
-	h = get_hierarchy(subsystem);
-	if (h) {
-		char *fullpath = must_make_path(h->fullcgpath, filename, NULL);
-		ret = lxc_write_to_file(fullpath, value, strlen(value), false);
-		free(fullpath);
+	h = get_hierarchy(controller);
+	if (!h) {
+		ERROR("Failed to setup limits for the \"%s\" controller. "
+		      "The controller seems to be unused by \"cgfsng\" cgroup "
+		      "driver or not enabled on the cgroup hierarchy",
+		      controller);
+		return -1;
 	}
+
+	fullpath = must_make_path(h->fullcgpath, filename, NULL);
+	ret = lxc_write_to_file(fullpath, value, strlen(value), false);
+	free(fullpath);
 	return ret;
 }