// 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 "export.h"
#include "accessors.h"
#include "super.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)) {
                if (btrfs_root_id(BTRFS_I(inode)->root) !=
                    btrfs_root_id(BTRFS_I(parent)->root))
                        *max_len = BTRFS_FID_SIZE_CONNECTABLE_ROOT;
                else
                        *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_root_id(BTRFS_I(inode)->root);
        fid->gen = inode->i_generation;

        if (parent) {
                u64 parent_root_id;

                fid->parent_objectid = btrfs_ino(BTRFS_I(parent));
                fid->parent_gen = parent->i_generation;
                parent_root_id = btrfs_root_id(BTRFS_I(parent)->root);

                if (parent_root_id != fid->root_objectid) {
                        if (*max_len < BTRFS_FID_SIZE_CONNECTABLE_ROOT)
                                return FILEID_INVALID;
                        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;
}

/*
 * Read dentry of inode with @objectid from filesystem root @root_objectid.
 *
 * @sb:             the filesystem super block
 * @objectid:       inode objectid
 * @root_objectid:  object id of the subvolume root where to look up the inode
 * @generation:     optional, if not zero, verify that the found inode
 *                  generation matches
 *
 * Return dentry alias for the inode, otherwise an error. In case the
 * generation does not match return ESTALE.
 */
struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
                                u64 root_objectid, u64 generation)
{
        struct btrfs_fs_info *fs_info = btrfs_sb(sb);
        struct btrfs_root *root;
        struct btrfs_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(objectid, root);
        btrfs_put_root(root);
        if (IS_ERR(inode))
                return ERR_CAST(inode);

        if (generation != 0 && generation != inode->vfs_inode.i_generation) {
                iput(&inode->vfs_inode);
                return ERR_PTR(-ESTALE);
        }

        return d_obtain_alias(&inode->vfs_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);
}

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);
}

struct dentry *btrfs_get_parent(struct dentry *child)
{
        struct btrfs_inode *dir = BTRFS_I(d_inode(child));
        struct btrfs_inode *inode;
        struct btrfs_root *root = dir->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        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(dir) == BTRFS_FIRST_FREE_OBJECTID) {
                key.objectid = btrfs_root_id(root);
                key.type = BTRFS_ROOT_BACKREF_KEY;
                key.offset = (u64)-1;
                root = fs_info->tree_root;
        } else {
                key.objectid = btrfs_ino(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;
        if (unlikely(ret == 0)) {
                /*
                 * Key with offset of -1 found, there would have to exist an
                 * inode with such number or a root with such id.
                 */
                ret = -EUCLEAN;
                goto fail;
        }

        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);
        }

        inode = btrfs_iget(key.objectid, root);
        if (IS_ERR(inode))
                return ERR_CAST(inode);

        return d_obtain_alias(&inode->vfs_inode);
fail:
        btrfs_free_path(path);
        return ERR_PTR(ret);
}

static int btrfs_get_name(struct dentry *parent, char *name,
                          struct dentry *child)
{
        struct btrfs_inode *inode = BTRFS_I(d_inode(child));
        struct btrfs_inode *dir = BTRFS_I(d_inode(parent));
        struct btrfs_root *root = dir->root;
        struct btrfs_fs_info *fs_info = root->fs_info;
        BTRFS_PATH_AUTO_FREE(path);
        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->vfs_inode.i_mode))
                return -EINVAL;

        ino = btrfs_ino(inode);

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        if (ino == BTRFS_FIRST_FREE_OBJECTID) {
                key.objectid = btrfs_root_id(inode->root);
                key.type = BTRFS_ROOT_BACKREF_KEY;
                key.offset = (u64)-1;
                root = fs_info->tree_root;
        } else {
                key.objectid = ino;
                key.type = BTRFS_INODE_REF_KEY;
                key.offset = btrfs_ino(dir);
        }

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0) {
                return ret;
        } else if (ret > 0) {
                if (ino == BTRFS_FIRST_FREE_OBJECTID)
                        path->slots[0]--;
                else
                        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);

        /*
         * 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,
};