From: Michael Tremer <michael.tremer@ipfire.org>
Date: Mon, 9 Dec 2024 17:20:07 +0000 (+0000)
Subject: cgroups: Keep a reference to the parent group
X-Git-Tag: 0.9.30~735
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4addfe61d9284007453c6e1766071c6b8e5d17a6;p=pakfire.git

cgroups: Keep a reference to the parent group

Since so many operations are recursive, this might be easier to handle.

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

diff --git a/src/libpakfire/cgroup.c b/src/libpakfire/cgroup.c
index e2679ecf3..75647be48 100644
--- a/src/libpakfire/cgroup.c
+++ b/src/libpakfire/cgroup.c
@@ -61,6 +61,9 @@ struct pakfire_cgroup {
 	struct pakfire_ctx* ctx;
 	int nrefs;
 
+	// The parent group
+	struct pakfire_cgroup* parent;
+
 	// Store the root path
 	char root[PATH_MAX];
 
@@ -77,11 +80,6 @@ struct pakfire_cgroup {
 	int devicesfd;
 };
 
-// Returns true if this is the root cgroup
-static int pakfire_cgroup_is_root(struct pakfire_cgroup* cgroup) {
-	return !*cgroup->path;
-}
-
 static int pakfire_cgroup_set_root(struct pakfire_cgroup* cgroup) {
 	int r;
 
@@ -108,21 +106,19 @@ static int pakfire_cgroup_set_root(struct pakfire_cgroup* cgroup) {
 }
 
 static const char* pakfire_cgroup_name(struct pakfire_cgroup* cgroup) {
-	if (pakfire_cgroup_is_root(cgroup))
+	if (!cgroup->parent)
 		return "(root)";
 
 	return cgroup->path;
 }
 
-static int pakfire_cgroup_parent(struct pakfire_cgroup* cgroup,  struct pakfire_cgroup** parent) {
+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)) {
-		*parent = NULL;
+	// If there is no path left, we have reached the root
+	if (!*cgroup->path)
 		return 0;
-	}
 
 	// Determine the path of the parent
 	r = pakfire_path_dirname(path, cgroup->path);
@@ -176,27 +172,12 @@ static int pakfire_cgroup_open_root(struct pakfire_cgroup* cgroup) {
 	int fd = open(cgroup->root, O_DIRECTORY|O_PATH|O_CLOEXEC);
 	if (fd < 0) {
 		ERROR(cgroup->ctx, "Could not open %s: %m\n", cgroup->root);
-		return -1;
+		return -errno;
 	}
 
 	return fd;
 }
 
-static int __pakfire_cgroup_create(struct pakfire_cgroup* cgroup) {
-	char path[PATH_MAX];
-	int r;
-
-	DEBUG(cgroup->ctx, "Trying to create cgroup %s\n", pakfire_cgroup_name(cgroup));
-
-	// Compose the absolute path
-	r = pakfire_path_append(path, cgroup->root, cgroup->path);
-	if (r)
-		return 1;
-
-	// Try creating the directory
-	return pakfire_mkdir(path, 0755);
-}
-
 /*
 	Opens the cgroup and returns a file descriptor.
 
@@ -204,44 +185,40 @@ static int __pakfire_cgroup_create(struct pakfire_cgroup* cgroup) {
 
 	This function returns a negative value on error.
 */
-static int __pakfire_cgroup_open(struct pakfire_cgroup* cgroup) {
+static int pakfire_cgroup_open(struct pakfire_cgroup* cgroup) {
+	char basename[NAME_MAX];
 	int fd = -EBADF;
 	int r;
 
-	// Open file descriptor of the cgroup root
-	int rootfd = pakfire_cgroup_open_root(cgroup);
-	if (rootfd < 0)
-		return rootfd;
+	// Open the root cgroup
+	if (!cgroup->parent)
+		return pakfire_cgroup_open_root(cgroup);
 
-	// Return the rootfd for the root group
-	if (pakfire_cgroup_is_root(cgroup))
-		return rootfd;
+	// Get the basename
+	r = pakfire_path_basename(basename, cgroup->path);
+	if (r < 0)
+		return r;
 
-RETRY:
-	fd = openat(rootfd, cgroup->path, O_DIRECTORY|O_PATH|O_CLOEXEC);
+	// Try to open the cgroup
+	fd = openat(cgroup->parent->fd, basename, O_DIRECTORY|O_PATH|O_CLOEXEC);
 	if (fd < 0) {
 		switch (errno) {
-			// If the cgroup doesn't exist yet, try to create it
 			case ENOENT:
-				r = __pakfire_cgroup_create(cgroup);
-				if (r)
-					goto ERROR;
+				r = mkdirat(cgroup->parent->fd, basename, 0755);
+				if (r < 0) {
+					ERROR(cgroup->ctx, "Could not create cgroup '%s': %m\n", basename);
+					return -errno;
+				}
 
-				// Retry open after successful creation
-				goto RETRY;
+				// Try opening it again
+				return pakfire_cgroup_open(cgroup);
 
-			// Exit on all other errors
 			default:
-				ERROR(cgroup->ctx, "Could not open cgroup %s: %m\n",
-					pakfire_cgroup_name(cgroup));
-				goto ERROR;
+				ERROR(cgroup->ctx, "Could not open cgroup '%s': %m\n", basename);
+				return -errno;
 		}
 	}
 
-ERROR:
-	if (rootfd > 0)
-		close(rootfd);
-
 	return fd;
 }
 
@@ -422,22 +399,27 @@ int pakfire_cgroup_create(struct pakfire_cgroup** cgroup,
 	// Copy flags
 	c->flags = flags;
 
+	// Find the parent cgroup
+	r = pakfire_cgroup_parent(c, &c->parent);
+	if (r < 0)
+		goto ERROR;
+
 	// Open a file descriptor
-	c->fd = __pakfire_cgroup_open(c);
-	if (c->fd < 0) {
-		r = 1;
+	c->fd = r = pakfire_cgroup_open(c);
+	if (r < 0)
 		goto ERROR;
-	}
 
 	// Enable all controllers
 	r = pakfire_cgroup_enable_controllers(c);
 	if (r < 0)
 		goto ERROR;
 
+#if 0
 	// Setup the devices filter
 	r = pakfire_cgroup_setup_devices(c);
 	if (r)
 		goto ERROR;
+#endif
 
 	// Return the pointer
 	*cgroup = pakfire_cgroup_ref(c);
@@ -454,6 +436,8 @@ static void pakfire_cgroup_free(struct pakfire_cgroup* cgroup) {
 		close(cgroup->fd);
 	if (cgroup->devicesfd >= 0)
 		close(cgroup->devicesfd);
+	if (cgroup->parent)
+		pakfire_cgroup_unref(cgroup->parent);
 	if (cgroup->ctx)
 		pakfire_ctx_unref(cgroup->ctx);
 	free(cgroup);
@@ -508,10 +492,8 @@ int pakfire_cgroup_destroy(struct pakfire_cgroup* cgroup) {
 	int r;
 
 	// Cannot call this for the root group
-	if (pakfire_cgroup_is_root(cgroup)) {
-		errno = EPERM;
-		return 1;
-	}
+	if (!cgroup->parent)
+		return -EPERM;
 
 	DEBUG(cgroup->ctx, "Destroying cgroup %s\n", pakfire_cgroup_name(cgroup));