1 files changed, 87 insertions, 7 deletions

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index d5b149a45be1..95a7c88baed9 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -16,6 +16,7 @@
 #include <linux/pagemap.h>
 #include <linux/namei.h>
 #include <linux/seq_file.h>
+#include <linux/exportfs.h>
 
 #include "kernfs-internal.h"
 
@@ -33,7 +34,7 @@ static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
 
 static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
 {
-	struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
+	struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
 	struct kernfs_syscall_ops *scops = root->syscall_ops;
 
 	if (scops && scops->show_options)
@@ -43,7 +44,7 @@ static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
 
 static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
 {
-	struct kernfs_node *node = dentry->d_fsdata;
+	struct kernfs_node *node = kernfs_dentry_node(dentry);
 	struct kernfs_root *root = kernfs_root(node);
 	struct kernfs_syscall_ops *scops = root->syscall_ops;
 
@@ -64,6 +65,78 @@ const struct super_operations kernfs_sops = {
 	.show_path	= kernfs_sop_show_path,
 };
 
+/*
+ * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
+ * number and generation
+ */
+struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
+	const union kernfs_node_id *id)
+{
+	struct kernfs_node *kn;
+
+	kn = kernfs_find_and_get_node_by_ino(root, id->ino);
+	if (!kn)
+		return NULL;
+	if (kn->id.generation != id->generation) {
+		kernfs_put(kn);
+		return NULL;
+	}
+	return kn;
+}
+
+static struct inode *kernfs_fh_get_inode(struct super_block *sb,
+		u64 ino, u32 generation)
+{
+	struct kernfs_super_info *info = kernfs_info(sb);
+	struct inode *inode;
+	struct kernfs_node *kn;
+
+	if (ino == 0)
+		return ERR_PTR(-ESTALE);
+
+	kn = kernfs_find_and_get_node_by_ino(info->root, ino);
+	if (!kn)
+		return ERR_PTR(-ESTALE);
+	inode = kernfs_get_inode(sb, kn);
+	kernfs_put(kn);
+	if (!inode)
+		return ERR_PTR(-ESTALE);
+
+	if (generation && inode->i_generation != generation) {
+		/* we didn't find the right inode.. */
+		iput(inode);
+		return ERR_PTR(-ESTALE);
+	}
+	return inode;
+}
+
+static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
+		int fh_len, int fh_type)
+{
+	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+				    kernfs_fh_get_inode);
+}
+
+static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid,
+		int fh_len, int fh_type)
+{
+	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
+				    kernfs_fh_get_inode);
+}
+
+static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
+{
+	struct kernfs_node *kn = kernfs_dentry_node(child);
+
+	return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
+}
+
+static const struct export_operations kernfs_export_ops = {
+	.fh_to_dentry	= kernfs_fh_to_dentry,
+	.fh_to_parent	= kernfs_fh_to_parent,
+	.get_parent	= kernfs_get_parent_dentry,
+};
+
 /**
  * kernfs_root_from_sb - determine kernfs_root associated with a super_block
  * @sb: the super_block in question
@@ -159,6 +232,8 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
 	sb->s_magic = magic;
 	sb->s_op = &kernfs_sops;
 	sb->s_xattr = kernfs_xattr_handlers;
+	if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
+		sb->s_export_op = &kernfs_export_ops;
 	sb->s_time_gran = 1;
 
 	/* get root inode, initialize and unlock it */
@@ -176,8 +251,6 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
 		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;
@@ -283,7 +356,6 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
 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;
 
 	mutex_lock(&kernfs_mutex);
 	list_del(&info->node);
@@ -295,7 +367,6 @@ void kernfs_kill_sb(struct super_block *sb)
 	 */
 	kill_anon_super(sb);
 	kfree(info);
-	kernfs_put(root_kn);
 }
 
 /**
@@ -330,7 +401,16 @@ struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
 
 void __init kernfs_init(void)
 {
+
+	/*
+	 * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
+	 * can access the slab lock free. This could introduce stale nodes,
+	 * please see how kernfs_find_and_get_node_by_ino filters out stale
+	 * nodes.
+	 */
 	kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
 					      sizeof(struct kernfs_node),
-					      0, SLAB_PANIC, NULL);
+					      0,
+					      SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,
+					      NULL);
 }