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vfs_inode.c

/*
 *  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 & 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;
      }

      return res;
}

int v9fs_uflags2omode(int uflags)
{
      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_EXCL)
            ret |= P9_OEXCL;

      if (uflags & O_TRUNC)
            ret |= P9_OTRUNC;

      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);
}
*/

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
 * @dentry:  dentry that is being created
 * @perm: create permissions
 * @mode: open mode
 *
 */
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
 * @inode: 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));
      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
 * @inode:  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_PTR(PTR_ERR(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
 * @buf: 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
 *
 */

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);
}

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 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
 *
 */

/* XXX - lots of code dup'd from symlink and creates,
 * figure out a better reuse strategy
 */

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
 * @dev_t: 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,
};

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