// SPDX-License-Identifier: GPL-2.0

  #include <linux/fs.h>
  #include <linux/types.h>
  #include "ctree.h"
  #include "disk-io.h"
  #include "btrfs_inode.h"
  #include "print-tree.h"
  #include "export.h"

  #define BTRFS_FID_SIZE_NON_CONNECTABLE (offsetof(struct btrfs_fid, \
  						 parent_objectid) / 4)
  #define BTRFS_FID_SIZE_CONNECTABLE (offsetof(struct btrfs_fid, \
  					     parent_root_objectid) / 4)
  #define BTRFS_FID_SIZE_CONNECTABLE_ROOT (sizeof(struct btrfs_fid) / 4)

  static int btrfs_encode_fh(struct inode *inode, u32 *fh, int *max_len,
  			   struct inode *parent)

  {
  	struct btrfs_fid *fid = (struct btrfs_fid *)fh;

  	int len = *max_len;
  	int type;

  	if (parent && (len < BTRFS_FID_SIZE_CONNECTABLE)) {

  		*max_len = BTRFS_FID_SIZE_CONNECTABLE;

  		return FILEID_INVALID;

  	} else if (len < BTRFS_FID_SIZE_NON_CONNECTABLE) {
  		*max_len = BTRFS_FID_SIZE_NON_CONNECTABLE;

  		return FILEID_INVALID;

  	}

  
  	len  = BTRFS_FID_SIZE_NON_CONNECTABLE;
  	type = FILEID_BTRFS_WITHOUT_PARENT;

  	fid->objectid = btrfs_ino(BTRFS_I(inode));

  	fid->root_objectid = BTRFS_I(inode)->root->root_key.objectid;

  	fid->gen = inode->i_generation;

  	if (parent) {

  		u64 parent_root_id;

  		fid->parent_objectid = BTRFS_I(parent)->location.objectid;
  		fid->parent_gen = parent->i_generation;

  		parent_root_id = BTRFS_I(parent)->root->root_key.objectid;

  		if (parent_root_id != fid->root_objectid) {
  			fid->parent_root_objectid = parent_root_id;
  			len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
  			type = FILEID_BTRFS_WITH_PARENT_ROOT;
  		} else {
  			len = BTRFS_FID_SIZE_CONNECTABLE;
  			type = FILEID_BTRFS_WITH_PARENT;
  		}
  	}
  
  	*max_len = len;
  	return type;
  }

  struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
  				u64 root_objectid, u32 generation,
  				int check_generation)

  {

  	struct btrfs_fs_info *fs_info = btrfs_sb(sb);

  	struct btrfs_root *root;
  	struct inode *inode;

  
  	if (objectid < BTRFS_FIRST_FREE_OBJECTID)
  		return ERR_PTR(-ESTALE);

  	root = btrfs_get_fs_root(fs_info, root_objectid, true);

  	if (IS_ERR(root))
  		return ERR_CAST(root);

  	inode = btrfs_iget(sb, objectid, root);

  	btrfs_put_root(root);

  	if (IS_ERR(inode))
  		return ERR_CAST(inode);

  	if (check_generation && generation != inode->i_generation) {

  		iput(inode);
  		return ERR_PTR(-ESTALE);
  	}

  	return d_obtain_alias(inode);

  }
  
  static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,
  					 int fh_len, int fh_type)
  {
  	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
  	u64 objectid, root_objectid;
  	u32 generation;
  
  	if (fh_type == FILEID_BTRFS_WITH_PARENT) {

  		if (fh_len <  BTRFS_FID_SIZE_CONNECTABLE)

  			return NULL;
  		root_objectid = fid->root_objectid;
  	} else if (fh_type == FILEID_BTRFS_WITH_PARENT_ROOT) {

  		if (fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)

  			return NULL;
  		root_objectid = fid->parent_root_objectid;
  	} else
  		return NULL;
  
  	objectid = fid->parent_objectid;
  	generation = fid->parent_gen;

  	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);

  }
  
  static struct dentry *btrfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
  					 int fh_len, int fh_type)
  {
  	struct btrfs_fid *fid = (struct btrfs_fid *) fh;
  	u64 objectid, root_objectid;
  	u32 generation;
  
  	if ((fh_type != FILEID_BTRFS_WITH_PARENT ||

  	     fh_len < BTRFS_FID_SIZE_CONNECTABLE) &&

  	    (fh_type != FILEID_BTRFS_WITH_PARENT_ROOT ||

  	     fh_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT) &&

  	    (fh_type != FILEID_BTRFS_WITHOUT_PARENT ||

  	     fh_len < BTRFS_FID_SIZE_NON_CONNECTABLE))

  		return NULL;
  
  	objectid = fid->objectid;
  	root_objectid = fid->root_objectid;
  	generation = fid->gen;

  	return btrfs_get_dentry(sb, objectid, root_objectid, generation, 1);

  }

  struct dentry *btrfs_get_parent(struct dentry *child)

  {

  	struct inode *dir = d_inode(child);

  	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);

  	struct btrfs_root *root = BTRFS_I(dir)->root;

  	struct btrfs_path *path;
  	struct extent_buffer *leaf;

  	struct btrfs_root_ref *ref;
  	struct btrfs_key key;
  	struct btrfs_key found_key;

  	int ret;
  
  	path = btrfs_alloc_path();

  	if (!path)
  		return ERR_PTR(-ENOMEM);

  	if (btrfs_ino(BTRFS_I(dir)) == BTRFS_FIRST_FREE_OBJECTID) {

  		key.objectid = root->root_key.objectid;
  		key.type = BTRFS_ROOT_BACKREF_KEY;
  		key.offset = (u64)-1;

  		root = fs_info->tree_root;

  	} else {

  		key.objectid = btrfs_ino(BTRFS_I(dir));

  		key.type = BTRFS_INODE_REF_KEY;
  		key.offset = (u64)-1;
  	}

  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);

  	if (ret < 0)
  		goto fail;

  	BUG_ON(ret == 0); /* Key with offset of -1 found */

  	if (path->slots[0] == 0) {
  		ret = -ENOENT;
  		goto fail;

  	}

  
  	path->slots[0]--;

  	leaf = path->nodes[0];

  
  	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
  	if (found_key.objectid != key.objectid || found_key.type != key.type) {
  		ret = -ENOENT;
  		goto fail;

  	}

  	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {
  		ref = btrfs_item_ptr(leaf, path->slots[0],
  				     struct btrfs_root_ref);
  		key.objectid = btrfs_root_ref_dirid(leaf, ref);
  	} else {
  		key.objectid = found_key.offset;
  	}

  	btrfs_free_path(path);

  	if (found_key.type == BTRFS_ROOT_BACKREF_KEY) {

  		return btrfs_get_dentry(fs_info->sb, key.objectid,

  					found_key.offset, 0, 0);
  	}

  	return d_obtain_alias(btrfs_iget(fs_info->sb, key.objectid, root));

  fail:
  	btrfs_free_path(path);
  	return ERR_PTR(ret);

  }

  static int btrfs_get_name(struct dentry *parent, char *name,
  			  struct dentry *child)
  {

  	struct inode *inode = d_inode(child);
  	struct inode *dir = d_inode(parent);

  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

  	struct btrfs_path *path;
  	struct btrfs_root *root = BTRFS_I(dir)->root;
  	struct btrfs_inode_ref *iref;
  	struct btrfs_root_ref *rref;
  	struct extent_buffer *leaf;
  	unsigned long name_ptr;
  	struct btrfs_key key;
  	int name_len;
  	int ret;

  	u64 ino;

  	if (!S_ISDIR(dir->i_mode))
  		return -EINVAL;

  	ino = btrfs_ino(BTRFS_I(inode));

  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  	path->leave_spinning = 1;

  	if (ino == BTRFS_FIRST_FREE_OBJECTID) {

  		key.objectid = BTRFS_I(inode)->root->root_key.objectid;
  		key.type = BTRFS_ROOT_BACKREF_KEY;
  		key.offset = (u64)-1;

  		root = fs_info->tree_root;

  	} else {

  		key.objectid = ino;

  		key.offset = btrfs_ino(BTRFS_I(dir));

  		key.type = BTRFS_INODE_REF_KEY;
  	}
  
  	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
  	if (ret < 0) {
  		btrfs_free_path(path);
  		return ret;
  	} else if (ret > 0) {

  		if (ino == BTRFS_FIRST_FREE_OBJECTID) {

  			path->slots[0]--;
  		} else {
  			btrfs_free_path(path);
  			return -ENOENT;
  		}
  	}
  	leaf = path->nodes[0];

  	if (ino == BTRFS_FIRST_FREE_OBJECTID) {
  		rref = btrfs_item_ptr(leaf, path->slots[0],

  				     struct btrfs_root_ref);

  		name_ptr = (unsigned long)(rref + 1);
  		name_len = btrfs_root_ref_name_len(leaf, rref);

  	} else {
  		iref = btrfs_item_ptr(leaf, path->slots[0],
  				      struct btrfs_inode_ref);
  		name_ptr = (unsigned long)(iref + 1);
  		name_len = btrfs_inode_ref_name_len(leaf, iref);
  	}
  
  	read_extent_buffer(leaf, name, name_ptr, name_len);
  	btrfs_free_path(path);
  
  	/*
  	 * have to add the null termination to make sure that reconnect_path
  	 * gets the right len for strlen
  	 */
  	name[name_len] = '\0';
  
  	return 0;
  }

  const struct export_operations btrfs_export_ops = {
  	.encode_fh	= btrfs_encode_fh,
  	.fh_to_dentry	= btrfs_fh_to_dentry,
  	.fh_to_parent	= btrfs_fh_to_parent,
  	.get_parent	= btrfs_get_parent,

  	.get_name	= btrfs_get_name,

  };