1 files changed, 171 insertions, 0 deletions

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
new file mode 100644
index 000000000000..0f4152defe7b
--- /dev/null
+++ b/fs/kernfs/mount.c
@@ -0,0 +1,171 @@
+/*
+ * fs/kernfs/mount.c - kernfs mount implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/init.h>
+#include <linux/magic.h>
+#include <linux/slab.h>
+#include <linux/pagemap.h>
+
+#include "kernfs-internal.h"
+
+struct kmem_cache *kernfs_node_cache;
+
+static const struct super_operations kernfs_sops = {
+        .statfs         = simple_statfs,
+        .drop_inode     = generic_delete_inode,
+        .evict_inode    = kernfs_evict_inode,
+};
+
+static int kernfs_fill_super(struct super_block *sb)
+{
+        struct kernfs_super_info *info = kernfs_info(sb);
+        struct inode *inode;
+        struct dentry *root;
+
+        sb->s_blocksize = PAGE_CACHE_SIZE;
+        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
+        sb->s_magic = SYSFS_MAGIC;
+        sb->s_op = &kernfs_sops;
+        sb->s_time_gran = 1;
+
+        /* get root inode, initialize and unlock it */
+        mutex_lock(&kernfs_mutex);
+        inode = kernfs_get_inode(sb, info->root->kn);
+        mutex_unlock(&kernfs_mutex);
+        if (!inode) {
+                pr_debug("kernfs: could not get root inode\n");
+                return -ENOMEM;
+        }
+
+        /* instantiate and link root dentry */
+        root = d_make_root(inode);
+        if (!root) {
+                pr_debug("%s: could not get root dentry!\n", __func__);
+                return -ENOMEM;
+        }
+        kernfs_get(info->root->kn);
+        root->d_fsdata = info->root->kn;
+        sb->s_root = root;
+        sb->s_d_op = &kernfs_dops;
+        return 0;
+}
+
+static int kernfs_test_super(struct super_block *sb, void *data)
+{
+        struct kernfs_super_info *sb_info = kernfs_info(sb);
+        struct kernfs_super_info *info = data;
+
+        return sb_info->root == info->root && sb_info->ns == info->ns;
+}
+
+static int kernfs_set_super(struct super_block *sb, void *data)
+{
+        int error;
+        error = set_anon_super(sb, data);
+        if (!error)
+                sb->s_fs_info = data;
+        return error;
+}
+
+/**
+ * kernfs_super_ns - determine the namespace tag of a kernfs super_block
+ * @sb: super_block of interest
+ *
+ * Return the namespace tag associated with kernfs super_block @sb.
+ */
+const void *kernfs_super_ns(struct super_block *sb)
+{
+        struct kernfs_super_info *info = kernfs_info(sb);
+
+        return info->ns;
+}
+
+/**
+ * kernfs_mount_ns - kernfs mount helper
+ * @fs_type: file_system_type of the fs being mounted
+ * @flags: mount flags specified for the mount
+ * @root: kernfs_root of the hierarchy being mounted
+ * @new_sb_created: tell the caller if we allocated a new superblock
+ * @ns: optional namespace tag of the mount
+ *
+ * This is to be called from each kernfs user's file_system_type->mount()
+ * implementation, which should pass through the specified @fs_type and
+ * @flags, and specify the hierarchy and namespace tag to mount via @root
+ * and @ns, respectively.
+ *
+ * The return value can be passed to the vfs layer verbatim.
+ */
+struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
+                               struct kernfs_root *root, bool *new_sb_created,
+                               const void *ns)
+{
+        struct super_block *sb;
+        struct kernfs_super_info *info;
+        int error;
+
+        info = kzalloc(sizeof(*info), GFP_KERNEL);
+        if (!info)
+                return ERR_PTR(-ENOMEM);
+
+        info->root = root;
+        info->ns = ns;
+
+        sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info);
+        if (IS_ERR(sb) || sb->s_fs_info != info)
+                kfree(info);
+        if (IS_ERR(sb))
+                return ERR_CAST(sb);
+
+        if (new_sb_created)
+                *new_sb_created = !sb->s_root;
+
+        if (!sb->s_root) {
+                error = kernfs_fill_super(sb);
+                if (error) {
+                        deactivate_locked_super(sb);
+                        return ERR_PTR(error);
+                }
+                sb->s_flags |= MS_ACTIVE;
+        }
+
+        return dget(sb->s_root);
+}
+
+/**
+ * kernfs_kill_sb - kill_sb for kernfs
+ * @sb: super_block being killed
+ *
+ * This can be used directly for file_system_type->kill_sb().  If a kernfs
+ * user needs extra cleanup, it can implement its own kill_sb() and call
+ * this function at the end.
+ */
+void kernfs_kill_sb(struct super_block *sb)
+{
+        struct kernfs_super_info *info = kernfs_info(sb);
+        struct kernfs_node *root_kn = sb->s_root->d_fsdata;
+
+        /*
+         * Remove the superblock from fs_supers/s_instances
+         * so we can't find it, before freeing kernfs_super_info.
+         */
+        kill_anon_super(sb);
+        kfree(info);
+        kernfs_put(root_kn);
+}
+
+void __init kernfs_init(void)
+{
+        kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
+                                              sizeof(struct kernfs_node),
+                                              0, SLAB_PANIC, NULL);
+        kernfs_inode_init();
+}