cgroup_do_mount(): massage calling conventions

pass it fs_context instead of fs_type/flags/root triple, have
it return int instead of dentry and make it deal with setting
fc->root.

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

3 files changed, 29 insertions, 36 deletions

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 3c1613a7648c..f7fd54f2973f 100644
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -212,8 +212,7 @@ void cgroup_free_root(struct cgroup_root *root);
 void init_cgroup_root(struct cgroup_fs_context *ctx);
 int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask);
 int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask);
-struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags,
-                               struct cgroup_root *root, unsigned long magic,
+int cgroup_do_mount(struct fs_context *fc, unsigned long magic,
                                struct cgroup_namespace *ns);
 
 int cgroup_migrate_vet_dst(struct cgroup *dst_cgrp);
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 45a198c63d6e..05f05d773adf 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -1141,7 +1141,6 @@ int cgroup1_get_tree(struct fs_context *fc)
         struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
         struct cgroup_root *root;
         struct cgroup_subsys *ss;
-        struct dentry *dentry;
         int i, ret;
 
         /* Check if the caller has permission to mount. */
@@ -1253,21 +1252,15 @@ out_free:
         if (ret)
                 return ret;
 
-        dentry = cgroup_do_mount(&cgroup_fs_type, fc->sb_flags, root,
-                                 CGROUP_SUPER_MAGIC, ns);
-        if (IS_ERR(dentry))
-                return PTR_ERR(dentry);
-
-        if (percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
-                struct super_block *sb = dentry->d_sb;
-                dput(dentry);
+        ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns);
+        if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) {
+                struct super_block *sb = fc->root->d_sb;
+                dput(fc->root);
                 deactivate_locked_super(sb);
                 msleep(10);
                 return restart_syscall();
         }
-
-        fc->root = dentry;
-        return 0;
+        return ret;
 }
 
 static int __init cgroup1_wq_init(void)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 57f43f63363a..64360a46d4df 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2036,43 +2036,48 @@ out:
         return ret;
 }
 
-struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags,
-                               struct cgroup_root *root, unsigned long magic,
-                               struct cgroup_namespace *ns)
+int cgroup_do_mount(struct fs_context *fc, unsigned long magic,
+                    struct cgroup_namespace *ns)
 {
-        struct dentry *dentry;
+        struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
         bool new_sb = false;
+        int ret = 0;
 
-        dentry = kernfs_mount(fs_type, flags, root->kf_root, magic, &new_sb);
+        fc->root = kernfs_mount(fc->fs_type, fc->sb_flags, ctx->root->kf_root,
+                                magic, &new_sb);
+        if (IS_ERR(fc->root))
+                ret = PTR_ERR(fc->root);
 
         /*
          * In non-init cgroup namespace, instead of root cgroup's dentry,
          * we return the dentry corresponding to the cgroupns->root_cgrp.
          */
-        if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
+        if (!ret && ns != &init_cgroup_ns) {
                 struct dentry *nsdentry;
-                struct super_block *sb = dentry->d_sb;
+                struct super_block *sb = fc->root->d_sb;
                 struct cgroup *cgrp;
 
                 mutex_lock(&cgroup_mutex);
                 spin_lock_irq(&css_set_lock);
 
-                cgrp = cset_cgroup_from_root(ns->root_cset, root);
+                cgrp = cset_cgroup_from_root(ns->root_cset, ctx->root);
 
                 spin_unlock_irq(&css_set_lock);
                 mutex_unlock(&cgroup_mutex);
 
                 nsdentry = kernfs_node_dentry(cgrp->kn, sb);
-                dput(dentry);
-                if (IS_ERR(nsdentry))
+                dput(fc->root);
+                fc->root = nsdentry;
+                if (IS_ERR(nsdentry)) {
+                        ret = PTR_ERR(nsdentry);
                         deactivate_locked_super(sb);
-                dentry = nsdentry;
+                }
         }
 
         if (!new_sb)
-                cgroup_put(&root->cgrp);
+                cgroup_put(&ctx->root->cgrp);
 
-        return dentry;
+        return ret;
 }
 
 /*
@@ -2091,7 +2096,7 @@ static int cgroup_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;
+        int ret;
 
         /* Check if the caller has permission to mount. */
         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
@@ -2101,14 +2106,10 @@ static int cgroup_get_tree(struct fs_context *fc)
         cgroup_get_live(&cgrp_dfl_root.cgrp);
         ctx->root = &cgrp_dfl_root;
 
-        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(ctx->flags);
-        fc->root = root;
-        return 0;
+        ret = cgroup_do_mount(fc, CGROUP2_SUPER_MAGIC, ns);
+        if (!ret)
+                apply_cgroup_root_flags(ctx->flags);
+        return ret;
 }
 
 static const struct fs_context_operations cgroup_fs_context_ops = {