/*
 *  linux/fs/9p/vfs_inode.c
 *
 * This file contains vfs inode ops for the 9P2000 protocol.
 *
 *  Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
 *  Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to:
 *  Free Software Foundation
 *  51 Franklin Street, Fifth Floor
 *  Boston, MA  02111-1301  USA
 *
 */

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/stat.h>
#include <linux/string.h>
#include <linux/inet.h>
#include <linux/namei.h>
#include <linux/idr.h>
#include <linux/sched.h>
#include <net/9p/9p.h>
#include <net/9p/client.h>

#include "v9fs.h"
#include "v9fs_vfs.h"
#include "fid.h"

static const struct inode_operations v9fs_dir_inode_operations;
static const struct inode_operations v9fs_dir_inode_operations_ext;
static const struct inode_operations v9fs_file_inode_operations;
static const struct inode_operations v9fs_symlink_inode_operations;

/**
 * unixmode2p9mode - convert unix mode bits to plan 9
 * @v9ses: v9fs session information
 * @mode: mode to convert
 *
 */

static int unixmode2p9mode(struct v9fs_session_info *v9ses, int mode)
{
        int res;
        res = mode & 0777;
        if (S_ISDIR(mode))
                res |= P9_DMDIR;
        if (v9fs_extended(v9ses)) {
                if (S_ISLNK(mode))
                        res |= P9_DMSYMLINK;
                if (v9ses->nodev == 0) {
                        if (S_ISSOCK(mode))
                                res |= P9_DMSOCKET;
                        if (S_ISFIFO(mode))
                                res |= P9_DMNAMEDPIPE;
                        if (S_ISBLK(mode))
                                res |= P9_DMDEVICE;
                        if (S_ISCHR(mode))
                                res |= P9_DMDEVICE;
                }

                if ((mode & S_ISUID) == S_ISUID)
                        res |= P9_DMSETUID;
                if ((mode & S_ISGID) == S_ISGID)
                        res |= P9_DMSETGID;
                if ((mode & S_ISVTX) == S_ISVTX)
                        res |= P9_DMSETVTX;
                if ((mode & P9_DMLINK))
                        res |= P9_DMLINK;
        }

        return res;
}

/**
 * p9mode2unixmode- convert plan9 mode bits to unix mode bits
 * @v9ses: v9fs session information
 * @mode: mode to convert
 *
 */

static int p9mode2unixmode(struct v9fs_session_info *v9ses, int mode)
{
        int res;

        res = mode & 0777;

        if ((mode & P9_DMDIR) == P9_DMDIR)
                res |= S_IFDIR;
        else if ((mode & P9_DMSYMLINK) && (v9fs_extended(v9ses)))
                res |= S_IFLNK;
        else if ((mode & P9_DMSOCKET) && (v9fs_extended(v9ses))
                 && (v9ses->nodev == 0))
                res |= S_IFSOCK;
        else if ((mode & P9_DMNAMEDPIPE) && (v9fs_extended(v9ses))
                 && (v9ses->nodev == 0))
                res |= S_IFIFO;
        else if ((mode & P9_DMDEVICE) && (v9fs_extended(v9ses))
                 && (v9ses->nodev == 0))
                res |= S_IFBLK;
        else
                res |= S_IFREG;

        if (v9fs_extended(v9ses)) {
                if ((mode & P9_DMSETUID) == P9_DMSETUID)
                        res |= S_ISUID;

                if ((mode & P9_DMSETGID) == P9_DMSETGID)
                        res |= S_ISGID;

                if ((mode & P9_DMSETVTX) == P9_DMSETVTX)
                        res |= S_ISVTX;
        }

        return res;
}

/**
 * v9fs_uflags2omode- convert posix open flags to plan 9 mode bits
 * @uflags: flags to convert
 * @extended: if .u extensions are active
 */

int v9fs_uflags2omode(int uflags, int extended)
{
        int ret;

        ret = 0;
        switch (uflags&3) {
        default:
        case O_RDONLY:
                ret = P9_OREAD;
                break;

        case O_WRONLY:
                ret = P9_OWRITE;
                break;

        case O_RDWR:
                ret = P9_ORDWR;
                break;
        }

        if (uflags & O_TRUNC)
                ret |= P9_OTRUNC;

        if (extended) {
                if (uflags & O_EXCL)
                        ret |= P9_OEXCL;

                if (uflags & O_APPEND)
                        ret |= P9_OAPPEND;
        }

        return ret;
}

/**
 * v9fs_blank_wstat - helper function to setup a 9P stat structure
 * @v9ses: 9P session info (for determining extended mode)
 * @wstat: structure to initialize
 *
 */

static void
v9fs_blank_wstat(struct p9_wstat *wstat)
{
        wstat->type = ~0;
        wstat->dev = ~0;
        wstat->qid.type = ~0;
        wstat->qid.version = ~0;
        *((long long *)&wstat->qid.path) = ~0;
        wstat->mode = ~0;
        wstat->atime = ~0;
        wstat->mtime = ~0;
        wstat->length = ~0;
        wstat->name = NULL;
        wstat->uid = NULL;
        wstat->gid = NULL;
        wstat->muid = NULL;
        wstat->n_uid = ~0;
        wstat->n_gid = ~0;
        wstat->n_muid = ~0;
        wstat->extension = NULL;
}

/**
 * v9fs_get_inode - helper function to setup an inode
 * @sb: superblock
 * @mode: mode to setup inode with
 *
 */

struct inode *v9fs_get_inode(struct super_block *sb, int mode)
{
        struct inode *inode;
        struct v9fs_session_info *v9ses = sb->s_fs_info;

        P9_DPRINTK(P9_DEBUG_VFS, "super block: %p mode: %o\n", sb, mode);

        inode = new_inode(sb);
        if (inode) {
                inode->i_mode = mode;
                inode->i_uid = current->fsuid;
                inode->i_gid = current->fsgid;
                inode->i_blocks = 0;
                inode->i_rdev = 0;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
                inode->i_mapping->a_ops = &v9fs_addr_operations;

                switch (mode & S_IFMT) {
                case S_IFIFO:
                case S_IFBLK:
                case S_IFCHR:
                case S_IFSOCK:
                        if (!v9fs_extended(v9ses)) {
                                P9_DPRINTK(P9_DEBUG_ERROR,
                                      "special files without extended mode\n");
                                return ERR_PTR(-EINVAL);
                        }
                        init_special_inode(inode, inode->i_mode,
                                           inode->i_rdev);
                        break;
                case S_IFREG:
                        inode->i_op = &v9fs_file_inode_operations;
                        inode->i_fop = &v9fs_file_operations;
                        break;
                case S_IFLNK:
                        if (!v9fs_extended(v9ses)) {
                                P9_DPRINTK(P9_DEBUG_ERROR,
                                        "extended modes used w/o 9P2000.u\n");
                                return ERR_PTR(-EINVAL);
                        }
                        inode->i_op = &v9fs_symlink_inode_operations;
                        break;
                case S_IFDIR:
                        inc_nlink(inode);
                        if (v9fs_extended(v9ses))
                                inode->i_op = &v9fs_dir_inode_operations_ext;
                        else
                                inode->i_op = &v9fs_dir_inode_operations;
                        inode->i_fop = &v9fs_dir_operations;
                        break;
                default:
                        P9_DPRINTK(P9_DEBUG_ERROR,
                                "BAD mode 0x%x S_IFMT 0x%x\n",
                                mode, mode & S_IFMT);
                        return ERR_PTR(-EINVAL);
                }
        } else {
                P9_EPRINTK(KERN_WARNING, "Problem allocating inode\n");
                return ERR_PTR(-ENOMEM);
        }
        return inode;
}

/*
static struct v9fs_fid*
v9fs_clone_walk(struct v9fs_session_info *v9ses, u32 fid, struct dentry *dentry)
{
        int err;
        int nfid;
        struct v9fs_fid *ret;
        struct v9fs_fcall *fcall;

        nfid = v9fs_get_idpool(&v9ses->fidpool);
        if (nfid < 0) {
                eprintk(KERN_WARNING, "no free fids available\n");
                return ERR_PTR(-ENOSPC);
        }

        err = v9fs_t_walk(v9ses, fid, nfid, (char *) dentry->d_name.name,
                &fcall);

        if (err < 0) {
                if (fcall && fcall->id == RWALK)
                        goto clunk_fid;

                PRINT_FCALL_ERROR("walk error", fcall);
                v9fs_put_idpool(nfid, &v9ses->fidpool);
                goto error;
        }

        kfree(fcall);
        fcall = NULL;
        ret = v9fs_fid_create(v9ses, nfid);
        if (!ret) {
                err = -ENOMEM;
                goto clunk_fid;
        }

        err = v9fs_fid_insert(ret, dentry);
        if (err < 0) {
                v9fs_fid_destroy(ret);
                goto clunk_fid;
        }

        return ret;

clunk_fid:
        v9fs_t_clunk(v9ses, nfid);

error:
        kfree(fcall);
        return ERR_PTR(err);
}
*/

/**
 * v9fs_inode_from_fid - populate an inode by issuing a attribute request
 * @v9ses: session information
 * @fid: fid to issue attribute request for
 * @sb: superblock on which to create inode
 *
 */

static struct inode *
v9fs_inode_from_fid(struct v9fs_session_info *v9ses, struct p9_fid *fid,
        struct super_block *sb)
{
        int err, umode;
        struct inode *ret;
        struct p9_stat *st;

        ret = NULL;
        st = p9_client_stat(fid);
        if (IS_ERR(st)) {
                err = PTR_ERR(st);
                st = NULL;
                goto error;
        }

        umode = p9mode2unixmode(v9ses, st->mode);
        ret = v9fs_get_inode(sb, umode);
        if (IS_ERR(ret)) {
                err = PTR_ERR(ret);
                ret = NULL;
                goto error;
        }

        v9fs_stat2inode(st, ret, sb);
        ret->i_ino = v9fs_qid2ino(&st->qid);
        kfree(st);
        return ret;

error:
        kfree(st);
        if (ret)
                iput(ret);

        return ERR_PTR(err);
}

/**
 * v9fs_remove - helper function to remove files and directories
 * @dir: directory inode that is being deleted
 * @file:  dentry that is being deleted
 * @rmdir: removing a directory
 *
 */

static int v9fs_remove(struct inode *dir, struct dentry *file, int rmdir)
{
        struct inode *file_inode;
        struct v9fs_session_info *v9ses;
        struct p9_fid *v9fid;

        P9_DPRINTK(P9_DEBUG_VFS, "inode: %p dentry: %p rmdir: %d\n", dir, file,
                rmdir);

        file_inode = file->d_inode;
        v9ses = v9fs_inode2v9ses(file_inode);
        v9fid = v9fs_fid_clone(file);
        if (IS_ERR(v9fid))
                return PTR_ERR(v9fid);

        return p9_client_remove(v9fid);
}

static int
v9fs_open_created(struct inode *inode, struct file *file)
{
        return 0;
}


/**
 * v9fs_create - Create a file
 * @v9ses: session information
 * @dir: directory that dentry is being created in
 * @dentry:  dentry that is being created
 * @perm: create permissions
 * @mode: open mode
 * @extension: 9p2000.u extension string to support devices, etc.
 *
 */
static struct p9_fid *
v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
                struct dentry *dentry, char *extension, u32 perm, u8 mode)
{
        int err;
        char *name;
        struct p9_fid *dfid, *ofid, *fid;
        struct inode *inode;

        err = 0;
        ofid = NULL;
        fid = NULL;
        name = (char *) dentry->d_name.name;
        dfid = v9fs_fid_clone(dentry->d_parent);
        if (IS_ERR(dfid)) {
                err = PTR_ERR(dfid);
                dfid = NULL;
                goto error;
        }

        /* clone a fid to use for creation */
        ofid = p9_client_walk(dfid, 0, NULL, 1);
        if (IS_ERR(ofid)) {
                err = PTR_ERR(ofid);
                ofid = NULL;
                goto error;
        }

        err = p9_client_fcreate(ofid, name, perm, mode, extension);
        if (err < 0)
                goto error;

        /* now walk from the parent so we can get unopened fid */
        fid = p9_client_walk(dfid, 1, &name, 0);
        if (IS_ERR(fid)) {
                err = PTR_ERR(fid);
                fid = NULL;
                goto error;
        } else
                dfid = NULL;

        /* instantiate inode and assign the unopened fid to the dentry */
        inode = v9fs_inode_from_fid(v9ses, fid, dir->i_sb);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto error;
        }

        if (v9ses->cache)
                dentry->d_op = &v9fs_cached_dentry_operations;
        else
                dentry->d_op = &v9fs_dentry_operations;

        d_instantiate(dentry, inode);
        v9fs_fid_add(dentry, fid);
        return ofid;

error:
        if (dfid)
                p9_client_clunk(dfid);

        if (ofid)
                p9_client_clunk(ofid);

        if (fid)
                p9_client_clunk(fid);

        return ERR_PTR(err);
}

/**
 * v9fs_vfs_create - VFS hook to create files
 * @dir: directory inode that is being created
 * @dentry:  dentry that is being deleted
 * @mode: create permissions
 * @nd: path information
 *
 */

static int
v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
                struct nameidata *nd)
{
        int err;
        u32 perm;
        int flags;
        struct v9fs_session_info *v9ses;
        struct p9_fid *fid;
        struct file *filp;

        err = 0;
        fid = NULL;
        v9ses = v9fs_inode2v9ses(dir);
        perm = unixmode2p9mode(v9ses, mode);
        if (nd && nd->flags & LOOKUP_OPEN)
                flags = nd->intent.open.flags - 1;
        else
                flags = O_RDWR;

        fid = v9fs_create(v9ses, dir, dentry, NULL, perm,
                                v9fs_uflags2omode(flags, v9fs_extended(v9ses)));
        if (IS_ERR(fid)) {
                err = PTR_ERR(fid);
                fid = NULL;
                goto error;
        }

        /* if we are opening a file, assign the open fid to the file */
        if (nd && nd->flags & LOOKUP_OPEN) {
                filp = lookup_instantiate_filp(nd, dentry, v9fs_open_created);
                if (IS_ERR(filp)) {
                        err = PTR_ERR(filp);
                        goto error;
                }

                filp->private_data = fid;
        } else
                p9_client_clunk(fid);

        return 0;

error:
        if (fid)
                p9_client_clunk(fid);

        return err;
}

/**
 * v9fs_vfs_mkdir - VFS mkdir hook to create a directory
 * @dir:  inode that is being unlinked
 * @dentry: dentry that is being unlinked
 * @mode: mode for new directory
 *
 */

static int v9fs_vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
        int err;
        u32 perm;
        struct v9fs_session_info *v9ses;
        struct p9_fid *fid;

        P9_DPRINTK(P9_DEBUG_VFS, "name %s\n", dentry->d_name.name);
        err = 0;
        v9ses = v9fs_inode2v9ses(dir);
        perm = unixmode2p9mode(v9ses, mode | S_IFDIR);
        fid = v9fs_create(v9ses, dir, dentry, NULL, perm, P9_OREAD);
        if (IS_ERR(fid)) {
                err = PTR_ERR(fid);
                fid = NULL;
        }

        if (fid)
                p9_client_clunk(fid);

        return err;
}

/**
 * v9fs_vfs_lookup - VFS lookup hook to "walk" to a new inode
 * @dir:  inode that is being walked from
 * @dentry: dentry that is being walked to?
 * @nameidata: path data
 *
 */

static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
                                      struct nameidata *nameidata)
{
        struct super_block *sb;
        struct v9fs_session_info *v9ses;
        struct p9_fid *dfid, *fid;
        struct inode *inode;
        char *name;
        int result = 0;

        P9_DPRINTK(P9_DEBUG_VFS, "dir: %p dentry: (%s) %p nameidata: %p\n",
                dir, dentry->d_name.name, dentry, nameidata);

        sb = dir->i_sb;
        v9ses = v9fs_inode2v9ses(dir);
        dfid = v9fs_fid_lookup(dentry->d_parent);
        if (IS_ERR(dfid))
                return ERR_CAST(dfid);

        name = (char *) dentry->d_name.name;
        fid = p9_client_walk(dfid, 1, &name, 1);
        if (IS_ERR(fid)) {
                result = PTR_ERR(fid);
                if (result == -ENOENT) {
                        d_add(dentry, NULL);
                        return NULL;
                }

                return ERR_PTR(result);
        }

        inode = v9fs_inode_from_fid(v9ses, fid, dir->i_sb);
        if (IS_ERR(inode)) {
                result = PTR_ERR(inode);
                inode = NULL;
                goto error;
        }

        result = v9fs_fid_add(dentry, fid);
        if (result < 0)
                goto error;

        if ((fid->qid.version) && (v9ses->cache))
                dentry->d_op = &v9fs_cached_dentry_operations;
        else
                dentry->d_op = &v9fs_dentry_operations;

        d_add(dentry, inode);
        return NULL;

error:
        if (fid)
                p9_client_clunk(fid);

        return ERR_PTR(result);
}

/**
 * v9fs_vfs_unlink - VFS unlink hook to delete an inode
 * @i:  inode that is being unlinked
 * @d: dentry that is being unlinked
 *
 */

static int v9fs_vfs_unlink(struct inode *i, struct dentry *d)
{
        return v9fs_remove(i, d, 0);
}

/**
 * v9fs_vfs_rmdir - VFS unlink hook to delete a directory
 * @i:  inode that is being unlinked
 * @d: dentry that is being unlinked
 *
 */

static int v9fs_vfs_rmdir(struct inode *i, struct dentry *d)
{
        return v9fs_remove(i, d, 1);
}

/**
 * v9fs_vfs_rename - VFS hook to rename an inode
 * @old_dir:  old dir inode
 * @old_dentry: old dentry
 * @new_dir: new dir inode
 * @new_dentry: new dentry
 *
 */

static int
v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                struct inode *new_dir, struct dentry *new_dentry)
{
        struct inode *old_inode;
        struct v9fs_session_info *v9ses;
        struct p9_fid *oldfid;
        struct p9_fid *olddirfid;
        struct p9_fid *newdirfid;
        struct p9_wstat wstat;
        int retval;

        P9_DPRINTK(P9_DEBUG_VFS, "\n");
        retval = 0;
        old_inode = old_dentry->d_inode;
        v9ses = v9fs_inode2v9ses(old_inode);
        oldfid = v9fs_fid_lookup(old_dentry);
        if (IS_ERR(oldfid))
                return PTR_ERR(oldfid);

        olddirfid = v9fs_fid_clone(old_dentry->d_parent);
        if (IS_ERR(olddirfid)) {
                retval = PTR_ERR(olddirfid);
                goto done;
        }

        newdirfid = v9fs_fid_clone(new_dentry->d_parent);
        if (IS_ERR(newdirfid)) {
                retval = PTR_ERR(newdirfid);
                goto clunk_olddir;
        }

        /* 9P can only handle file rename in the same directory */
        if (memcmp(&olddirfid->qid, &newdirfid->qid, sizeof(newdirfid->qid))) {
                P9_DPRINTK(P9_DEBUG_ERROR,
                                "old dir and new dir are different\n");
                retval = -EXDEV;
                goto clunk_newdir;
        }

        v9fs_blank_wstat(&wstat);
        wstat.muid = v9ses->uname;
        wstat.name = (char *) new_dentry->d_name.name;
        retval = p9_client_wstat(oldfid, &wstat);

clunk_newdir:
        p9_client_clunk(newdirfid);

clunk_olddir:
        p9_client_clunk(olddirfid);

done:
        return retval;
}

/**
 * v9fs_vfs_getattr - retrieve file metadata
 * @mnt: mount information
 * @dentry: file to get attributes on
 * @stat: metadata structure to populate
 *
 */

static int
v9fs_vfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
                 struct kstat *stat)
{
        int err;
        struct v9fs_session_info *v9ses;
        struct p9_fid *fid;
        struct p9_stat *st;

        P9_DPRINTK(P9_DEBUG_VFS, "dentry: %p\n", dentry);
        err = -EPERM;
        v9ses = v9fs_inode2v9ses(dentry->d_inode);
        if (v9ses->cache == CACHE_LOOSE)
                return simple_getattr(mnt, dentry, stat);

        fid = v9fs_fid_lookup(dentry);
        if (IS_ERR(fid))
                return PTR_ERR(fid);

        st = p9_client_stat(fid);
        if (IS_ERR(st))
                return PTR_ERR(st);

        v9fs_stat2inode(st, dentry->d_inode, dentry->d_inode->i_sb);
                generic_fillattr(dentry->d_inode, stat);

        kfree(st);
        return 0;
}

/**
 * v9fs_vfs_setattr - set file metadata
 * @dentry: file whose metadata to set
 * @iattr: metadata assignment structure
 *
 */

static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
        int retval;
        struct v9fs_session_info *v9ses;
        struct p9_fid *fid;
        struct p9_wstat wstat;

        P9_DPRINTK(P9_DEBUG_VFS, "\n");
        retval = -EPERM;
        v9ses = v9fs_inode2v9ses(dentry->d_inode);
        fid = v9fs_fid_lookup(dentry);
        if(IS_ERR(fid))
                return PTR_ERR(fid);

        v9fs_blank_wstat(&wstat);
        if (iattr->ia_valid & ATTR_MODE)
                wstat.mode = unixmode2p9mode(v9ses, iattr->ia_mode);

        if (iattr->ia_valid & ATTR_MTIME)
                wstat.mtime = iattr->ia_mtime.tv_sec;

        if (iattr->ia_valid & ATTR_ATIME)
                wstat.atime = iattr->ia_atime.tv_sec;

        if (iattr->ia_valid & ATTR_SIZE)
                wstat.length = iattr->ia_size;

        if (v9fs_extended(v9ses)) {
                if (iattr->ia_valid & ATTR_UID)
                        wstat.n_uid = iattr->ia_uid;

                if (iattr->ia_valid & ATTR_GID)
                        wstat.n_gid = iattr->ia_gid;
        }

        retval = p9_client_wstat(fid, &wstat);
        if (retval >= 0)
                retval = inode_setattr(dentry->d_inode, iattr);

        return retval;
}

/**
 * v9fs_stat2inode - populate an inode structure with mistat info
 * @stat: Plan 9 metadata (mistat) structure
 * @inode: inode to populate
 * @sb: superblock of filesystem
 *
 */

void
v9fs_stat2inode(struct p9_stat *stat, struct inode *inode,
        struct super_block *sb)
{
        int n;
        char ext[32];
        struct v9fs_session_info *v9ses = sb->s_fs_info;

        inode->i_nlink = 1;

        inode->i_atime.tv_sec = stat->atime;
        inode->i_mtime.tv_sec = stat->mtime;
        inode->i_ctime.tv_sec = stat->mtime;

        inode->i_uid = v9ses->dfltuid;
        inode->i_gid = v9ses->dfltgid;

        if (v9fs_extended(v9ses)) {
                inode->i_uid = stat->n_uid;
                inode->i_gid = stat->n_gid;
        }

        inode->i_mode = p9mode2unixmode(v9ses, stat->mode);
        if ((S_ISBLK(inode->i_mode)) || (S_ISCHR(inode->i_mode))) {
                char type = 0;
                int major = -1;
                int minor = -1;

                n = stat->extension.len;
                if (n > sizeof(ext)-1)
                        n = sizeof(ext)-1;
                memmove(ext, stat->extension.str, n);
                ext[n] = 0;
                sscanf(ext, "%c %u %u", &type, &major, &minor);
                switch (type) {
                case 'c':
                        inode->i_mode &= ~S_IFBLK;
                        inode->i_mode |= S_IFCHR;
                        break;
                case 'b':
                        break;
                default:
                        P9_DPRINTK(P9_DEBUG_ERROR,
                                "Unknown special type %c (%.*s)\n", type,
                                stat->extension.len, stat->extension.str);
                };
                inode->i_rdev = MKDEV(major, minor);
        } else
                inode->i_rdev = 0;

        inode->i_size = stat->length;

        /* not real number of blocks, but 512 byte ones ... */
        inode->i_blocks = (inode->i_size + 512 - 1) >> 9;
}

/**
 * v9fs_qid2ino - convert qid into inode number
 * @qid: qid to hash
 *
 * BUG: potential for inode number collisions?
 */

ino_t v9fs_qid2ino(struct p9_qid *qid)
{
        u64 path = qid->path + 2;
        ino_t i = 0;

        if (sizeof(ino_t) == sizeof(path))
                memcpy(&i, &path, sizeof(ino_t));
        else
                i = (ino_t) (path ^ (path >> 32));

        return i;
}

/**
 * v9fs_readlink - read a symlink's location (internal version)
 * @dentry: dentry for symlink
 * @buffer: buffer to load symlink location into
 * @buflen: length of buffer
 *
 */

static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
{
        int retval;

        struct v9fs_session_info *v9ses;
        struct p9_fid *fid;
        struct p9_stat *st;

        P9_DPRINTK(P9_DEBUG_VFS, " %s\n", dentry->d_name.name);
        retval = -EPERM;
        v9ses = v9fs_inode2v9ses(dentry->d_inode);
        fid = v9fs_fid_lookup(dentry);
        if (IS_ERR(fid))
                return PTR_ERR(fid);

        if (!v9fs_extended(v9ses))
                return -EBADF;

        st = p9_client_stat(fid);
        if (IS_ERR(st))
                return PTR_ERR(st);

        if (!(st->mode & P9_DMSYMLINK)) {
                retval = -EINVAL;
                goto done;
        }

        /* copy extension buffer into buffer */
        if (st->extension.len < buflen)
                buflen = st->extension.len + 1;

        memmove(buffer, st->extension.str, buflen - 1);
        buffer[buflen-1] = 0;

        P9_DPRINTK(P9_DEBUG_VFS,
                "%s -> %.*s (%s)\n", dentry->d_name.name, st->extension.len,
                st->extension.str, buffer);

        retval = buflen;

done:
        kfree(st);
        return retval;
}

/**
 * v9fs_vfs_readlink - read a symlink's location
 * @dentry: dentry for symlink
 * @buffer: buffer to load symlink location into
 * @buflen: length of buffer
 *
 */

static int v9fs_vfs_readlink(struct dentry *dentry, char __user * buffer,
                             int buflen)
{
        int retval;
        int ret;
        char *link = __getname();

        if (unlikely(!link))
                return -ENOMEM;

        if (buflen > PATH_MAX)
                buflen = PATH_MAX;

        P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_iname, dentry);

        retval = v9fs_readlink(dentry, link, buflen);

        if (retval > 0) {
                if ((ret = copy_to_user(buffer, link, retval)) != 0) {
                        P9_DPRINTK(P9_DEBUG_ERROR,
                                        "problem copying to user: %d\n", ret);
                        retval = ret;
                }
        }

        __putname(link);
        return retval;
}

/**
 * v9fs_vfs_follow_link - follow a symlink path
 * @dentry: dentry for symlink
 * @nd: nameidata
 *
 */

static void *v9fs_vfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
        int len = 0;
        char *link = __getname();

        P9_DPRINTK(P9_DEBUG_VFS, "%s n", dentry->d_name.name);

        if (!link)
                link = ERR_PTR(-ENOMEM);
        else {

                len = v9fs_readlink(dentry, link, PATH_MAX);

                if (len < 0) {
                        __putname(link);
                        link = ERR_PTR(len);
                } else
                        link[len] = 0;
        }
        nd_set_link(nd, link);

        return NULL;
}

/**
 * v9fs_vfs_put_link - release a symlink path
 * @dentry: dentry for symlink
 * @nd: nameidata
 * @p: unused
 *
 */

static void
v9fs_vfs_put_link(struct dentry *dentry, struct nameidata *nd, void *p)
{
        char *s = nd_get_link(nd);

        P9_DPRINTK(P9_DEBUG_VFS, " %s %s\n", dentry->d_name.name, s);
        if (!IS_ERR(s))
                __putname(s);
}

/**
 * v9fs_vfs_mkspecial - create a special file
 * @dir: inode to create special file in
 * @dentry: dentry to create
 * @mode: mode to create special file
 * @extension: 9p2000.u format extension string representing special file
 *
 */

static int v9fs_vfs_mkspecial(struct inode *dir, struct dentry *dentry,
        int mode, const char *extension)
{
        u32 perm;
        struct v9fs_session_info *v9ses;
        struct p9_fid *fid;

        v9ses = v9fs_inode2v9ses(dir);
        if (!v9fs_extended(v9ses)) {
                P9_DPRINTK(P9_DEBUG_ERROR, "not extended\n");
                return -EPERM;
        }

        perm = unixmode2p9mode(v9ses, mode);
        fid = v9fs_create(v9ses, dir, dentry, (char *) extension, perm,
                                                                P9_OREAD);
        if (IS_ERR(fid))
                return PTR_ERR(fid);

        p9_client_clunk(fid);
        return 0;
}

/**
 * v9fs_vfs_symlink - helper function to create symlinks
 * @dir: directory inode containing symlink
 * @dentry: dentry for symlink
 * @symname: symlink data
 *
 * See Also: 9P2000.u RFC for more information
 *
 */

static int
v9fs_vfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
{
        P9_DPRINTK(P9_DEBUG_VFS, " %lu,%s,%s\n", dir->i_ino,
                                        dentry->d_name.name, symname);

        return v9fs_vfs_mkspecial(dir, dentry, S_IFLNK, symname);
}

/**
 * v9fs_vfs_link - create a hardlink
 * @old_dentry: dentry for file to link to
 * @dir: inode destination for new link
 * @dentry: dentry for link
 *
 */

static int
v9fs_vfs_link(struct dentry *old_dentry, struct inode *dir,
              struct dentry *dentry)
{
        int retval;
        struct p9_fid *oldfid;
        char *name;

        P9_DPRINTK(P9_DEBUG_VFS,
                " %lu,%s,%s\n", dir->i_ino, dentry->d_name.name,
                old_dentry->d_name.name);

        oldfid = v9fs_fid_clone(old_dentry);
        if (IS_ERR(oldfid))
                return PTR_ERR(oldfid);

        name = __getname();
        if (unlikely(!name)) {
                retval = -ENOMEM;
                goto clunk_fid;
        }

        sprintf(name, "%d\n", oldfid->fid);
        retval = v9fs_vfs_mkspecial(dir, dentry, P9_DMLINK, name);
        __putname(name);

clunk_fid:
        p9_client_clunk(oldfid);
        return retval;
}

/**
 * v9fs_vfs_mknod - create a special file
 * @dir: inode destination for new link
 * @dentry: dentry for file
 * @mode: mode for creation
 * @rdev: device associated with special file
 *
 */

static int
v9fs_vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t rdev)
{
        int retval;
        char *name;

        P9_DPRINTK(P9_DEBUG_VFS,
                " %lu,%s mode: %x MAJOR: %u MINOR: %u\n", dir->i_ino,
                dentry->d_name.name, mode, MAJOR(rdev), MINOR(rdev));

        if (!new_valid_dev(rdev))
                return -EINVAL;

        name = __getname();
        if (!name)
                return -ENOMEM;
        /* build extension */
        if (S_ISBLK(mode))
                sprintf(name, "b %u %u", MAJOR(rdev), MINOR(rdev));
        else if (S_ISCHR(mode))
                sprintf(name, "c %u %u", MAJOR(rdev), MINOR(rdev));
        else if (S_ISFIFO(mode))
                *name = 0;
        else {
                __putname(name);
                return -EINVAL;
        }

        retval = v9fs_vfs_mkspecial(dir, dentry, mode, name);
        __putname(name);

        return retval;
}

static const struct inode_operations v9fs_dir_inode_operations_ext = {
        .create = v9fs_vfs_create,
        .lookup = v9fs_vfs_lookup,
        .symlink = v9fs_vfs_symlink,
        .link = v9fs_vfs_link,
        .unlink = v9fs_vfs_unlink,
        .mkdir = v9fs_vfs_mkdir,
        .rmdir = v9fs_vfs_rmdir,
        .mknod = v9fs_vfs_mknod,
        .rename = v9fs_vfs_rename,
        .readlink = v9fs_vfs_readlink,
        .getattr = v9fs_vfs_getattr,
        .setattr = v9fs_vfs_setattr,
};

static const struct inode_operations v9fs_dir_inode_operations = {
        .create = v9fs_vfs_create,
        .lookup = v9fs_vfs_lookup,
        .unlink = v9fs_vfs_unlink,
        .mkdir = v9fs_vfs_mkdir,
        .rmdir = v9fs_vfs_rmdir,
        .mknod = v9fs_vfs_mknod,
        .rename = v9fs_vfs_rename,
        .getattr = v9fs_vfs_getattr,
        .setattr = v9fs_vfs_setattr,
};

static const struct inode_operations v9fs_file_inode_operations = {
        .getattr = v9fs_vfs_getattr,
        .setattr = v9fs_vfs_setattr,
};

static const struct inode_operations v9fs_symlink_inode_operations = {
        .readlink = v9fs_vfs_readlink,
        .follow_link = v9fs_vfs_follow_link,
        .put_link = v9fs_vfs_put_link,
        .getattr = v9fs_vfs_getattr,
        .setattr = v9fs_vfs_setattr,
};