// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2015, Primary Data, Inc. All rights reserved.
 *
 * Tao Peng <bergwolf@primarydata.com>
 */
#include <linux/dcache.h>
#include <linux/exportfs.h>
#include <linux/nfs.h>
#include <linux/nfs_fs.h>

#include "internal.h"
#include "nfstrace.h"

#define NFSDBG_FACILITY         NFSDBG_VFS

enum {
        FILEID_HIGH_OFF = 0,    /* inode fileid high */
        FILEID_LOW_OFF,         /* inode fileid low */
        FILE_I_TYPE_OFF,        /* inode type */
        EMBED_FH_OFF            /* embeded server fh */
};


static struct nfs_fh *nfs_exp_embedfh(__u32 *p)
{
        return (struct nfs_fh *)(p + EMBED_FH_OFF);
}

/*
 * Let's break subtree checking for now... otherwise we'll have to embed parent fh
 * but there might not be enough space.
 */
static int
nfs_encode_fh(struct inode *inode, __u32 *p, int *max_len, struct inode *parent)
{
        struct nfs_fh *server_fh = NFS_FH(inode);
        struct nfs_fh *clnt_fh = nfs_exp_embedfh(p);
        size_t fh_size = offsetof(struct nfs_fh, data) + server_fh->size;
        int len = EMBED_FH_OFF + XDR_QUADLEN(fh_size);

        dprintk("%s: max fh len %d inode %p parent %p",
                __func__, *max_len, inode, parent);

        if (*max_len < len) {
                dprintk("%s: fh len %d too small, required %d\n",
                        __func__, *max_len, len);
                *max_len = len;
                return FILEID_INVALID;
        }

        p[FILEID_HIGH_OFF] = NFS_FILEID(inode) >> 32;
        p[FILEID_LOW_OFF] = NFS_FILEID(inode);
        p[FILE_I_TYPE_OFF] = inode->i_mode & S_IFMT;
        p[len - 1] = 0; /* Padding */
        nfs_copy_fh(clnt_fh, server_fh);
        *max_len = len;
        dprintk("%s: result fh fileid %llu mode %u size %d\n",
                __func__, NFS_FILEID(inode), inode->i_mode, *max_len);
        return *max_len;
}

static struct dentry *
nfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
                 int fh_len, int fh_type)
{
        struct nfs_fattr *fattr = NULL;
        struct nfs_fh *server_fh = nfs_exp_embedfh(fid->raw);
        size_t fh_size = offsetof(struct nfs_fh, data);
        const struct nfs_rpc_ops *rpc_ops;
        struct dentry *dentry;
        struct inode *inode;
        int len = EMBED_FH_OFF;
        u32 *p = fid->raw;
        int ret;

        /* Initial check of bounds */
        if (fh_len < len + XDR_QUADLEN(fh_size) ||
            fh_len > XDR_QUADLEN(NFS_MAXFHSIZE))
                return NULL;
        /* Calculate embedded filehandle size */
        fh_size += server_fh->size;
        len += XDR_QUADLEN(fh_size);
        /* NULL translates to ESTALE */
        if (fh_len < len || fh_type != len)
                return NULL;

        fattr = nfs_alloc_fattr_with_label(NFS_SB(sb));
        if (fattr == NULL) {
                dentry = ERR_PTR(-ENOMEM);
                goto out;
        }

        fattr->fileid = ((u64)p[FILEID_HIGH_OFF] << 32) + p[FILEID_LOW_OFF];
        fattr->mode = p[FILE_I_TYPE_OFF];
        fattr->valid |= NFS_ATTR_FATTR_FILEID | NFS_ATTR_FATTR_TYPE;

        dprintk("%s: fileid %llu mode %d\n", __func__, fattr->fileid, fattr->mode);

        inode = nfs_ilookup(sb, fattr, server_fh);
        if (inode)
                goto out_found;

        rpc_ops = NFS_SB(sb)->nfs_client->rpc_ops;
        ret = rpc_ops->getattr(NFS_SB(sb), server_fh, fattr, NULL);
        if (ret) {
                dprintk("%s: getattr failed %d\n", __func__, ret);
                trace_nfs_fh_to_dentry(sb, server_fh, fattr->fileid, ret);
                dentry = ERR_PTR(ret);
                goto out_free_fattr;
        }

        inode = nfs_fhget(sb, server_fh, fattr);

out_found:
        dentry = d_obtain_alias(inode);
out_free_fattr:
        nfs_free_fattr(fattr);
out:
        return dentry;
}

static struct dentry *
nfs_get_parent(struct dentry *dentry)
{
        int ret;
        struct inode *inode = d_inode(dentry), *pinode;
        struct super_block *sb = inode->i_sb;
        struct nfs_server *server = NFS_SB(sb);
        struct nfs_fattr *fattr = NULL;
        struct dentry *parent;
        struct nfs_rpc_ops const *ops = server->nfs_client->rpc_ops;
        struct nfs_fh fh;

        if (!ops->lookupp)
                return ERR_PTR(-EACCES);

        fattr = nfs_alloc_fattr_with_label(server);
        if (fattr == NULL)
                return ERR_PTR(-ENOMEM);

        ret = ops->lookupp(inode, &fh, fattr);
        if (ret) {
                parent = ERR_PTR(ret);
                goto out;
        }

        pinode = nfs_fhget(sb, &fh, fattr);
        parent = d_obtain_alias(pinode);
out:
        nfs_free_fattr(fattr);
        return parent;
}

const struct export_operations nfs_export_ops = {
        .encode_fh = nfs_encode_fh,
        .fh_to_dentry = nfs_fh_to_dentry,
        .get_parent = nfs_get_parent,
        .flags = EXPORT_OP_NOWCC                |
                 EXPORT_OP_NOSUBTREECHK         |
                 EXPORT_OP_CLOSE_BEFORE_UNLINK  |
                 EXPORT_OP_REMOTE_FS            |
                 EXPORT_OP_NOATOMIC_ATTR        |
                 EXPORT_OP_FLUSH_ON_CLOSE       |
                 EXPORT_OP_NOLOCKS,
};