cgroup2: switch to option-by-option parsing

[again, carved out of patch by dhowells]
[NB: we probably want to handle "source" in parse_param here]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index faba00caa1979e7a126327da75f38af68deea30f..d0cddfbdf5cfc6d6d6f35a1987ff925384ece4f9 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -54,6 +54,7 @@
 #include <linux/proc_ns.h>
 #include <linux/nsproxy.h>
 #include <linux/file.h>
+#include <linux/fs_parser.h>
 #include <linux/sched/cputime.h>
 #include <linux/psi.h>
 #include <net/sock.h>
@@ -1772,26 +1773,37 @@ int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
        return len;
 }
 
-static int parse_cgroup_root_flags(char *data, unsigned int *root_flags)
-{
-       char *token;
+enum cgroup2_param {
+       Opt_nsdelegate,
+       nr__cgroup2_params
+};
 
-       *root_flags = 0;
+static const struct fs_parameter_spec cgroup2_param_specs[] = {
+       fsparam_flag  ("nsdelegate",            Opt_nsdelegate),
+       {}
+};
 
-       if (!data || *data == '\0')
-               return 0;
+static const struct fs_parameter_description cgroup2_fs_parameters = {
+       .name           = "cgroup2",
+       .specs          = cgroup2_param_specs,
+};
 
-       while ((token = strsep(&data, ",")) != NULL) {
-               if (!strcmp(token, "nsdelegate")) {
-                       *root_flags |= CGRP_ROOT_NS_DELEGATE;
-                       continue;
-               }
+static int cgroup2_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+       struct fs_parse_result result;
+       int opt;
 
-               pr_err("cgroup2: unknown option \"%s\"\n", token);
-               return -EINVAL;
-       }
+       opt = fs_parse(fc, &cgroup2_fs_parameters, param, &result);
+       if (opt < 0)
+               return opt;
 
-       return 0;
+       switch (opt) {
+       case Opt_nsdelegate:
+               ctx->flags |= CGRP_ROOT_NS_DELEGATE;
+               return 0;
+       }
+       return -EINVAL;
 }
 
 static void apply_cgroup_root_flags(unsigned int root_flags)
@@ -2074,15 +2086,6 @@ static void cgroup_fs_context_free(struct fs_context *fc)
        kfree(ctx);
 }
 
-static int cgroup_parse_monolithic(struct fs_context *fc, void *data)
-{
-       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
-
-       if (data)
-               security_sb_eat_lsm_opts(data, &fc->security);
-       return parse_cgroup_root_flags(data, &ctx->flags);
-}
-
 static int cgroup_get_tree(struct fs_context *fc)
 {
        struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
@@ -2108,7 +2111,7 @@ static int cgroup_get_tree(struct fs_context *fc)
 
 static const struct fs_context_operations cgroup_fs_context_ops = {
        .free           = cgroup_fs_context_free,
-       .parse_monolithic = cgroup_parse_monolithic,
+       .parse_param    = cgroup2_parse_param,
        .get_tree       = cgroup_get_tree,
        .reconfigure    = cgroup_reconfigure,
 };
@@ -2174,10 +2177,11 @@ struct file_system_type cgroup_fs_type = {
 };
 
 static struct file_system_type cgroup2_fs_type = {
-       .name = "cgroup2",
-       .init_fs_context = cgroup_init_fs_context,
-       .kill_sb = cgroup_kill_sb,
-       .fs_flags = FS_USERNS_MOUNT,
+       .name                   = "cgroup2",
+       .init_fs_context        = cgroup_init_fs_context,
+       .parameters             = &cgroup2_fs_parameters,
+       .kill_sb                = cgroup_kill_sb,
+       .fs_flags               = FS_USERNS_MOUNT,
 };
 
 int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,