From: Michael Tremer <michael.tremer@ipfire.org>
Date: Mon, 9 Dec 2024 16:29:06 +0000 (+0000)
Subject: cgroups: Implement recursively enabling controllers
X-Git-Tag: 0.9.30~739
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d81b74edae492f732354b11507f5cd01f788a6e1;p=pakfire.git

cgroups: Implement recursively enabling controllers

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---

diff --git a/src/libpakfire/cgroup.c b/src/libpakfire/cgroup.c
index 1550c93a5..8b3848981 100644
--- a/src/libpakfire/cgroup.c
+++ b/src/libpakfire/cgroup.c
@@ -114,34 +114,25 @@ static const char* pakfire_cgroup_name(struct pakfire_cgroup* cgroup) {
 	return cgroup->path;
 }
 
-static struct pakfire_cgroup* pakfire_cgroup_parent(struct pakfire_cgroup* cgroup) {
-	struct pakfire_cgroup* parent = NULL;
+static int pakfire_cgroup_parent(struct pakfire_cgroup* cgroup,  struct pakfire_cgroup** parent) {
 	char path[PATH_MAX];
 	int r;
 
 	// Cannot return parent for root group
-	if (pakfire_cgroup_is_root(cgroup))
-		return NULL;
+	if (pakfire_cgroup_is_root(cgroup)) {
+		*parent = NULL;
+		return 0;
+	}
 
 	// Determine the path of the parent
 	r = pakfire_path_dirname(path, cgroup->path);
-	if (r) {
-		ERROR(cgroup->ctx, "Could not determine path for parent cgroup: %m\n");
-		return NULL;
+	if (r < 0) {
+		ERROR(cgroup->ctx, "Could not determine path for parent cgroup: %s\n", strerror(-r));
+		return r;
 	}
 
-	// dirname() returns . if no directory component could be found
-	if (strcmp(path, ".") == 0)
-		*path = '\0';
-
 	// Open the cgroup
-	r = pakfire_cgroup_open(&parent, cgroup->ctx, path, 0);
-	if (r) {
-		ERROR(cgroup->ctx, "Could not open parent cgroup: %m\n");
-		parent = NULL;
-	}
-
-	return parent;
+	return pakfire_cgroup_open(parent, cgroup->ctx, path, 0);
 }
 
 static int pakfire_cgroup_setup_devices(struct pakfire_cgroup* cgroup) {
@@ -296,27 +287,29 @@ static int pakfire_cgroup_write(struct pakfire_cgroup* cgroup,
 
 static int pakfire_cgroup_write(struct pakfire_cgroup* cgroup,
 		const char* path, const char* format, ...) {
+	ssize_t bytes_written = 0;
 	va_list args;
+	int fd = -EBADF;
 	int r = 0;
 
 	// Check if this cgroup has been destroyed already
 	if (cgroup->fd < 0) {
 		ERROR(cgroup->ctx, "Trying to write to destroyed cgroup\n");
-		errno = EPERM;
-		return 1;
+		return -EPERM;
 	}
 
 	// Open the file
-	int fd = openat(cgroup->fd, path, O_WRONLY|O_CLOEXEC);
+	fd = openat(cgroup->fd, path, O_WRONLY|O_CLOEXEC);
 	if (fd < 0) {
 		DEBUG(cgroup->ctx, "Could not open %s/%s for writing: %m\n",
 			pakfire_cgroup_name(cgroup), path);
-		return -errno;
+		r = -errno;
+		goto ERROR;
 	}
 
 	// Write buffer
 	va_start(args, format);
-	ssize_t bytes_written = vdprintf(fd, format, args);
+	bytes_written = vdprintf(fd, format, args);
 	va_end(args);
 
 	// Check if content was written okay
@@ -324,10 +317,12 @@ static int pakfire_cgroup_write(struct pakfire_cgroup* cgroup,
 		DEBUG(cgroup->ctx, "Could not write to %s/%s: %m\n",
 			pakfire_cgroup_name(cgroup), path);
 		r = -errno;
+		goto ERROR;
 	}
 
-	// Close fd
-	close(fd);
+ERROR:
+	if (fd > 0)
+		close(fd);
 
 	return r;
 }
@@ -336,12 +331,37 @@ static int pakfire_cgroup_write(struct pakfire_cgroup* cgroup,
 	Enables a cgroup controller.
 */
 static int pakfire_cgroup_enable_controller(struct pakfire_cgroup* cgroup, const char* name) {
+	struct pakfire_cgroup* parent = NULL;
 	int r;
 
 	// Try to enable the controller
 	r = pakfire_cgroup_write(cgroup, "cgroup.subtree_control", "+%s", name);
-	if (r < 0)
-		ERROR(cgroup->ctx, "Could not enable controller '%s': %s\n", name, strerror(-r));
+	if (r < 0) {
+		switch (-r) {
+			case ENOENT:
+				// Fetch the parent group
+				r = pakfire_cgroup_parent(cgroup, &parent);
+				if (r < 0)
+					return r;
+
+				// When we have reached root, we cannot continue
+				if (!parent)
+					return -ENOTSUP;
+
+				// Ensure it is enabled there
+				r = pakfire_cgroup_enable_controller(parent, name);
+				if (r < 0)
+					return 0;
+
+				// Once that was successful, try again
+				return pakfire_cgroup_enable_controller(cgroup, name);
+
+			default:
+				ERROR(cgroup->ctx, "Could not enable controller '%s': %s\n",
+					name, strerror(-r));
+				break;
+		}
+	}
 
 	return r;
 }