cgroup: start switching to fs_context

Unfortunately, cgroup is tangled into kernfs infrastructure.
To avoid converting all kernfs-based filesystems at once,
we need to untangle the remount part of things, instead of
having it go through kernfs_sop_remount_fs().  Fortunately,
it's not hard to do.

This commit just gets cgroup/cgroup1 to use fs_context to
deliver options on mount and remount paths.  Parsing those
is going to be done in the next commits; for now we do
pretty much what legacy case does.

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

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index c9a35f09e4b9f1706ea02807c0bf925c55b316e8..a89cb0ba7a68b7cc1743b078da295642025fc6ba 100644 (file)
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -7,6 +7,7 @@
 #include <linux/workqueue.h>
 #include <linux/list.h>
 #include <linux/refcount.h>
+#include <linux/fs_context.h>
 
 #define TRACE_CGROUP_PATH_LEN 1024
 extern spinlock_t trace_cgroup_path_lock;
@@ -36,6 +37,18 @@ extern void __init enable_debug_cgroup(void);
                }                                                       \
        } while (0)
 
+/*
+ * The cgroup filesystem superblock creation/mount context.
+ */
+struct cgroup_fs_context {
+       char *data;
+};
+
+static inline struct cgroup_fs_context *cgroup_fc2context(struct fs_context *fc)
+{
+       return fc->fs_private;
+}
+
 /*
  * A cgroup can be associated with multiple css_sets as different tasks may
  * belong to different cgroups on different hierarchies.  In the other
@@ -255,5 +268,6 @@ void cgroup1_check_for_release(struct cgroup *cgrp);
 struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
                             void *data, unsigned long magic,
                             struct cgroup_namespace *ns);
+int cgroup1_reconfigure(struct fs_context *ctx);
 
 #endif /* __CGROUP_INTERNAL_H */

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index f94a7229974e4d2c028e84f8abaa2e1077d3bd46..e377e19dd3e626c32a96c4da4c02a63c61d6e864 100644 (file)
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -1046,17 +1046,19 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
        return 0;
 }
 
-static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
+int cgroup1_reconfigure(struct fs_context *fc)
 {
-       int ret = 0;
+       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+       struct kernfs_root *kf_root = kernfs_root_from_sb(fc->root->d_sb);
        struct cgroup_root *root = cgroup_root_from_kf(kf_root);
+       int ret = 0;
        struct cgroup_sb_opts opts;
        u16 added_mask, removed_mask;
 
        cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
 
        /* See what subsystems are wanted */
-       ret = parse_cgroupfs_options(data, &opts);
+       ret = parse_cgroupfs_options(ctx->data, &opts);
        if (ret)
                goto out_unlock;
 
@@ -1106,7 +1108,6 @@ static int cgroup1_remount(struct kernfs_root *kf_root, int *flags, char *data)
 struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
        .rename                 = cgroup1_rename,
        .show_options           = cgroup1_show_options,
-       .remount_fs             = cgroup1_remount,
        .mkdir                  = cgroup_mkdir,
        .rmdir                  = cgroup_rmdir,
        .show_path              = cgroup_show_path,

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 7fd9f22e406d7646706d00288ccea4f2b753c33c..7f7db5f967e3eeb247f1a8fd4a816eb0aa6f2664 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1811,12 +1811,13 @@ static int cgroup_show_options(struct seq_file *seq, struct kernfs_root *kf_root
        return 0;
 }
 
-static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
+static int cgroup_reconfigure(struct fs_context *fc)
 {
+       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
        unsigned int root_flags;
        int ret;
 
-       ret = parse_cgroup_root_flags(data, &root_flags);
+       ret = parse_cgroup_root_flags(ctx->data, &root_flags);
        if (ret)
                return ret;
 
@@ -2067,21 +2068,98 @@ struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags,
        return dentry;
 }
 
-static struct dentry *cgroup_mount(struct file_system_type *fs_type,
-                        int flags, const char *unused_dev_name,
-                        void *data)
+/*
+ * Destroy a cgroup filesystem context.
+ */
+static void cgroup_fs_context_free(struct fs_context *fc)
+{
+       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+
+       kfree(ctx);
+}
+
+static int cgroup_parse_monolithic(struct fs_context *fc, void *data)
+{
+       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+
+       ctx->data = data;
+       if (ctx->data)
+               security_sb_eat_lsm_opts(ctx->data, &fc->security);
+       return 0;
+}
+
+static int cgroup_get_tree(struct fs_context *fc)
 {
        struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
-       struct dentry *dentry;
+       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+       unsigned int root_flags;
+       struct dentry *root;
        int ret;
 
-       get_cgroup_ns(ns);
+       /* Check if the caller has permission to mount. */
+       if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+               return -EPERM;
+
+       ret = parse_cgroup_root_flags(ctx->data, &root_flags);
+       if (ret)
+               return ret;
+
+       cgrp_dfl_visible = true;
+       cgroup_get_live(&cgrp_dfl_root.cgrp);
+
+       root = cgroup_do_mount(&cgroup2_fs_type, fc->sb_flags, &cgrp_dfl_root,
+                                        CGROUP2_SUPER_MAGIC, ns);
+       if (IS_ERR(root))
+               return PTR_ERR(root);
+
+       apply_cgroup_root_flags(root_flags);
+       fc->root = root;
+       return 0;
+}
+
+static int cgroup1_get_tree(struct fs_context *fc)
+{
+       struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
+       struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
+       struct dentry *root;
 
        /* Check if the caller has permission to mount. */
-       if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
-               put_cgroup_ns(ns);
-               return ERR_PTR(-EPERM);
-       }
+       if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
+               return -EPERM;
+
+       root = cgroup1_mount(&cgroup_fs_type, fc->sb_flags, ctx->data,
+                                      CGROUP_SUPER_MAGIC, ns);
+       if (IS_ERR(root))
+               return PTR_ERR(root);
+
+       fc->root = root;
+       return 0;
+}
+
+static const struct fs_context_operations cgroup_fs_context_ops = {
+       .free           = cgroup_fs_context_free,
+       .parse_monolithic = cgroup_parse_monolithic,
+       .get_tree       = cgroup_get_tree,
+       .reconfigure    = cgroup_reconfigure,
+};
+
+static const struct fs_context_operations cgroup1_fs_context_ops = {
+       .free           = cgroup_fs_context_free,
+       .parse_monolithic = cgroup_parse_monolithic,
+       .get_tree       = cgroup1_get_tree,
+       .reconfigure    = cgroup1_reconfigure,
+};
+
+/*
+ * Initialise the cgroup filesystem creation/reconfiguration context.
+ */
+static int cgroup_init_fs_context(struct fs_context *fc)
+{
+       struct cgroup_fs_context *ctx;
+
+       ctx = kzalloc(sizeof(struct cgroup_fs_context), GFP_KERNEL);
+       if (!ctx)
+               return -ENOMEM;
 
        /*
         * The first time anyone tries to mount a cgroup, enable the list
@@ -2090,29 +2168,12 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
        if (!use_task_css_set_links)
                cgroup_enable_task_cg_lists();
 
-       if (fs_type == &cgroup2_fs_type) {
-               unsigned int root_flags;
-
-               ret = parse_cgroup_root_flags(data, &root_flags);
-               if (ret) {
-                       put_cgroup_ns(ns);
-                       return ERR_PTR(ret);
-               }
-
-               cgrp_dfl_visible = true;
-               cgroup_get_live(&cgrp_dfl_root.cgrp);
-
-               dentry = cgroup_do_mount(&cgroup2_fs_type, flags, &cgrp_dfl_root,
-                                        CGROUP2_SUPER_MAGIC, ns);
-               if (!IS_ERR(dentry))
-                       apply_cgroup_root_flags(root_flags);
-       } else {
-               dentry = cgroup1_mount(&cgroup_fs_type, flags, data,
-                                      CGROUP_SUPER_MAGIC, ns);
-       }
-
-       put_cgroup_ns(ns);
-       return dentry;
+       fc->fs_private = ctx;
+       if (fc->fs_type == &cgroup2_fs_type)
+               fc->ops = &cgroup_fs_context_ops;
+       else
+               fc->ops = &cgroup1_fs_context_ops;
+       return 0;
 }
 
 static void cgroup_kill_sb(struct super_block *sb)
@@ -2136,14 +2197,14 @@ static void cgroup_kill_sb(struct super_block *sb)
 
 struct file_system_type cgroup_fs_type = {
        .name = "cgroup",
-       .mount = cgroup_mount,
+       .init_fs_context = cgroup_init_fs_context,
        .kill_sb = cgroup_kill_sb,
        .fs_flags = FS_USERNS_MOUNT,
 };
 
 static struct file_system_type cgroup2_fs_type = {
        .name = "cgroup2",
-       .mount = cgroup_mount,
+       .init_fs_context = cgroup_init_fs_context,
        .kill_sb = cgroup_kill_sb,
        .fs_flags = FS_USERNS_MOUNT,
 };
@@ -5268,7 +5329,6 @@ int cgroup_rmdir(struct kernfs_node *kn)
 
 static struct kernfs_syscall_ops cgroup_kf_syscall_ops = {
        .show_options           = cgroup_show_options,
-       .remount_fs             = cgroup_remount,
        .mkdir                  = cgroup_mkdir,
        .rmdir                  = cgroup_rmdir,
        .show_path              = cgroup_show_path,