/*
   *  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
   *
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #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 <linux/slab.h>

  #include <linux/xattr.h>

  #include <linux/posix_acl.h>

  #include <net/9p/9p.h>
  #include <net/9p/client.h>

  #include "v9fs.h"

  #include "v9fs_vfs.h"

  #include "fid.h"

  #include "cache.h"

  #include "xattr.h"

  #include "acl.h"

  static const struct inode_operations v9fs_dir_inode_operations;

  static const struct inode_operations v9fs_dir_inode_operations_dotu;

  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 u32 unixmode2p9mode(struct v9fs_session_info *v9ses, umode_t mode)

  {
  	int res;
  	res = mode & 0777;
  	if (S_ISDIR(mode))

  		res |= P9_DMDIR;

  	if (v9fs_proto_dotu(v9ses)) {

  		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;

  	}

  	return res;
  }
  
  /**

   * p9mode2perm- convert plan9 mode bits to unix permission bits
   * @v9ses: v9fs session information
   * @stat: p9_wstat from which mode need to be derived
   *
   */
  static int p9mode2perm(struct v9fs_session_info *v9ses,
  		       struct p9_wstat *stat)
  {
  	int res;
  	int mode = stat->mode;
  
  	res = mode & S_IALLUGO;
  	if (v9fs_proto_dotu(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;
  }
  
  /**

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

   * @stat: p9_wstat from which mode need to be derived
   * @rdev: major number, minor number in case of device files.

   *
   */

  static umode_t p9mode2unixmode(struct v9fs_session_info *v9ses,
  			       struct p9_wstat *stat, dev_t *rdev)

  {
  	int res;

  	u32 mode = stat->mode;

  	*rdev = 0;

  	res = p9mode2perm(v9ses, stat);

  	if ((mode & P9_DMDIR) == P9_DMDIR)

  		res |= S_IFDIR;

  	else if ((mode & P9_DMSYMLINK) && (v9fs_proto_dotu(v9ses)))

  		res |= S_IFLNK;

  	else if ((mode & P9_DMSOCKET) && (v9fs_proto_dotu(v9ses))

  		 && (v9ses->nodev == 0))
  		res |= S_IFSOCK;

  	else if ((mode & P9_DMNAMEDPIPE) && (v9fs_proto_dotu(v9ses))

  		 && (v9ses->nodev == 0))
  		res |= S_IFIFO;

  	else if ((mode & P9_DMDEVICE) && (v9fs_proto_dotu(v9ses))

  		 && (v9ses->nodev == 0)) {
  		char type = 0, ext[32];
  		int major = -1, minor = -1;
  
  		strncpy(ext, stat->extension, sizeof(ext));
  		sscanf(ext, "%c %u %u", &type, &major, &minor);
  		switch (type) {
  		case 'c':
  			res |= S_IFCHR;
  			break;
  		case 'b':
  			res |= S_IFBLK;
  			break;
  		default:

  			p9_debug(P9_DEBUG_ERROR, "Unknown special type %c %s
  ",
  				 type, stat->extension);

  		};
  		*rdev = MKDEV(major, minor);
  	} else

  		res |= S_IFREG;

  	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

   * @wstat: structure to initialize

   *
   */

  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_alloc_inode - helper function to allocate an inode

   *
   */

  struct inode *v9fs_alloc_inode(struct super_block *sb)
  {

  	struct v9fs_inode *v9inode;
  	v9inode = (struct v9fs_inode *)kmem_cache_alloc(v9fs_inode_cache,
  							GFP_KERNEL);
  	if (!v9inode)

  		return NULL;

  #ifdef CONFIG_9P_FSCACHE
  	v9inode->fscache = NULL;

  	spin_lock_init(&v9inode->fscache_lock);
  #endif

  	v9inode->writeback_fid = NULL;

  	v9inode->cache_validity = 0;

  	mutex_init(&v9inode->v_mutex);

  	return &v9inode->vfs_inode;

  }
  
  /**
   * v9fs_destroy_inode - destroy an inode
   *
   */

  static void v9fs_i_callback(struct rcu_head *head)

  {

  	struct inode *inode = container_of(head, struct inode, i_rcu);

  	kmem_cache_free(v9fs_inode_cache, V9FS_I(inode));

  }

  
  void v9fs_destroy_inode(struct inode *inode)
  {
  	call_rcu(&inode->i_rcu, v9fs_i_callback);
  }

  int v9fs_init_inode(struct v9fs_session_info *v9ses,

  		    struct inode *inode, umode_t mode, dev_t rdev)

  {

  	int err = 0;

  	inode_init_owner(inode, NULL, mode);

  	inode->i_blocks = 0;

  	inode->i_rdev = rdev;

  	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_proto_dotl(v9ses)) {
  			inode->i_op = &v9fs_file_inode_operations_dotl;

  		} else if (v9fs_proto_dotu(v9ses)) {
  			inode->i_op = &v9fs_file_inode_operations;

  		} else {

  			p9_debug(P9_DEBUG_ERROR,
  				 "special files without extended mode
  ");

  			err = -EINVAL;
  			goto error;

  		}

  		init_special_inode(inode, inode->i_mode, inode->i_rdev);
  		break;
  	case S_IFREG:

  		if (v9fs_proto_dotl(v9ses)) {
  			inode->i_op = &v9fs_file_inode_operations_dotl;

  			if (v9ses->cache)
  				inode->i_fop =
  					&v9fs_cached_file_operations_dotl;
  			else
  				inode->i_fop = &v9fs_file_operations_dotl;

  		} else {
  			inode->i_op = &v9fs_file_inode_operations;

  			if (v9ses->cache)
  				inode->i_fop = &v9fs_cached_file_operations;
  			else
  				inode->i_fop = &v9fs_file_operations;

  		}

  		break;
  	case S_IFLNK:

  		if (!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses)) {

  			p9_debug(P9_DEBUG_ERROR,
  				 "extended modes used with legacy protocol
  ");

  			err = -EINVAL;
  			goto error;
  		}

  
  		if (v9fs_proto_dotl(v9ses))
  			inode->i_op = &v9fs_symlink_inode_operations_dotl;
  		else
  			inode->i_op = &v9fs_symlink_inode_operations;

  		break;
  	case S_IFDIR:
  		inc_nlink(inode);

  		if (v9fs_proto_dotl(v9ses))
  			inode->i_op = &v9fs_dir_inode_operations_dotl;
  		else if (v9fs_proto_dotu(v9ses))
  			inode->i_op = &v9fs_dir_inode_operations_dotu;

  		else
  			inode->i_op = &v9fs_dir_inode_operations;

  
  		if (v9fs_proto_dotl(v9ses))
  			inode->i_fop = &v9fs_dir_operations_dotl;
  		else
  			inode->i_fop = &v9fs_dir_operations;

  		break;
  	default:

  		p9_debug(P9_DEBUG_ERROR, "BAD mode 0x%hx S_IFMT 0x%x
  ",

  			 mode, mode & S_IFMT);

  		err = -EINVAL;
  		goto error;

  	}

  error:
  	return err;

  }

  /**
   * 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, umode_t mode, dev_t rdev)

  {
  	int err;
  	struct inode *inode;
  	struct v9fs_session_info *v9ses = sb->s_fs_info;

  	p9_debug(P9_DEBUG_VFS, "super block: %p mode: %ho
  ", sb, mode);

  
  	inode = new_inode(sb);
  	if (!inode) {

  		pr_warn("%s (%d): Problem allocating inode
  ",
  			__func__, task_pid_nr(current));

  		return ERR_PTR(-ENOMEM);
  	}

  	err = v9fs_init_inode(v9ses, inode, mode, rdev);

  	if (err) {
  		iput(inode);
  		return ERR_PTR(err);
  	}
  	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
  ");

  		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_clear_inode - release an inode
   * @inode: inode to release
   *
   */

  void v9fs_evict_inode(struct inode *inode)

  {

  	struct v9fs_inode *v9inode = V9FS_I(inode);

  	truncate_inode_pages(inode->i_mapping, 0);
  	end_writeback(inode);

  	filemap_fdatawrite(inode->i_mapping);
  
  #ifdef CONFIG_9P_FSCACHE
  	v9fs_cache_inode_put_cookie(inode);
  #endif

  	/* clunk the fid stashed in writeback_fid */
  	if (v9inode->writeback_fid) {
  		p9_client_clunk(v9inode->writeback_fid);
  		v9inode->writeback_fid = NULL;

  	}

  }

  static int v9fs_test_inode(struct inode *inode, void *data)
  {
  	int umode;

  	dev_t rdev;

  	struct v9fs_inode *v9inode = V9FS_I(inode);
  	struct p9_wstat *st = (struct p9_wstat *)data;
  	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(inode);

  	umode = p9mode2unixmode(v9ses, st, &rdev);

  	/* don't match inode of different type */
  	if ((inode->i_mode & S_IFMT) != (umode & S_IFMT))
  		return 0;
  
  	/* compare qid details */
  	if (memcmp(&v9inode->qid.version,
  		   &st->qid.version, sizeof(v9inode->qid.version)))
  		return 0;
  
  	if (v9inode->qid.type != st->qid.type)
  		return 0;
  	return 1;
  }

  static int v9fs_test_new_inode(struct inode *inode, void *data)
  {
  	return 0;
  }

  static int v9fs_set_inode(struct inode *inode,  void *data)
  {
  	struct v9fs_inode *v9inode = V9FS_I(inode);
  	struct p9_wstat *st = (struct p9_wstat *)data;
  
  	memcpy(&v9inode->qid, &st->qid, sizeof(st->qid));
  	return 0;
  }

  static struct inode *v9fs_qid_iget(struct super_block *sb,
  				   struct p9_qid *qid,

  				   struct p9_wstat *st,
  				   int new)

  {

  	dev_t rdev;

  	int retval;
  	umode_t umode;

  	unsigned long i_ino;
  	struct inode *inode;
  	struct v9fs_session_info *v9ses = sb->s_fs_info;

  	int (*test)(struct inode *, void *);
  
  	if (new)
  		test = v9fs_test_new_inode;
  	else
  		test = v9fs_test_inode;

  	i_ino = v9fs_qid2ino(qid);

  	inode = iget5_locked(sb, i_ino, test, v9fs_set_inode, st);

  	if (!inode)
  		return ERR_PTR(-ENOMEM);
  	if (!(inode->i_state & I_NEW))
  		return inode;
  	/*
  	 * initialize the inode with the stat info
  	 * FIXME!! we may need support for stale inodes
  	 * later.
  	 */

  	inode->i_ino = i_ino;

  	umode = p9mode2unixmode(v9ses, st, &rdev);
  	retval = v9fs_init_inode(v9ses, inode, umode, rdev);

  	if (retval)

  		goto error;

  	v9fs_stat2inode(st, inode, sb);

  #ifdef CONFIG_9P_FSCACHE

  	v9fs_cache_inode_get_cookie(inode);

  #endif

  	unlock_new_inode(inode);
  	return inode;

  error:

  	unlock_new_inode(inode);
  	iput(inode);
  	return ERR_PTR(retval);
  
  }
  
  struct inode *

  v9fs_inode_from_fid(struct v9fs_session_info *v9ses, struct p9_fid *fid,

  		    struct super_block *sb, int new)

  {
  	struct p9_wstat *st;
  	struct inode *inode = NULL;
  
  	st = p9_client_stat(fid);
  	if (IS_ERR(st))
  		return ERR_CAST(st);

  	inode = v9fs_qid_iget(sb, &st->qid, st, new);

  	p9stat_free(st);

  	kfree(st);

  	return inode;

  }
  
  /**

   * v9fs_at_to_dotl_flags- convert Linux specific AT flags to
   * plan 9 AT flag.
   * @flags: flags to convert
   */
  static int v9fs_at_to_dotl_flags(int flags)
  {
  	int rflags = 0;
  	if (flags & AT_REMOVEDIR)
  		rflags |= P9_DOTL_AT_REMOVEDIR;
  	return rflags;
  }
  
  /**

   * v9fs_remove - helper function to remove files and directories

   * @dir: directory inode that is being deleted

   * @dentry:  dentry that is being deleted

   * @rmdir: removing a directory

   *
   */

  static int v9fs_remove(struct inode *dir, struct dentry *dentry, int flags)

  {

  	struct inode *inode;
  	int retval = -EOPNOTSUPP;
  	struct p9_fid *v9fid, *dfid;
  	struct v9fs_session_info *v9ses;

  	p9_debug(P9_DEBUG_VFS, "inode: %p dentry: %p rmdir: %x
  ",
  		 dir, dentry, flags);

  	v9ses = v9fs_inode2v9ses(dir);
  	inode = dentry->d_inode;
  	dfid = v9fs_fid_lookup(dentry->d_parent);
  	if (IS_ERR(dfid)) {
  		retval = PTR_ERR(dfid);

  		p9_debug(P9_DEBUG_VFS, "fid lookup failed %d
  ", retval);

  		return retval;
  	}
  	if (v9fs_proto_dotl(v9ses))

  		retval = p9_client_unlinkat(dfid, dentry->d_name.name,
  					    v9fs_at_to_dotl_flags(flags));

  	if (retval == -EOPNOTSUPP) {
  		/* Try the one based on path */
  		v9fid = v9fs_fid_clone(dentry);
  		if (IS_ERR(v9fid))
  			return PTR_ERR(v9fid);
  		retval = p9_client_remove(v9fid);
  	}

  	if (!retval) {
  		/*
  		 * directories on unlink should have zero
  		 * link count
  		 */

  		if (flags & AT_REMOVEDIR) {
  			clear_nlink(inode);

  			drop_nlink(dir);
  		} else

  			drop_nlink(inode);

  		v9fs_invalidate_inode_attr(inode);

  		v9fs_invalidate_inode_attr(dir);

  	}

  	return retval;

  }
  
  /**

   * v9fs_create - Create a file

   * @v9ses: session information
   * @dir: directory that dentry is being created in

   * @dentry:  dentry that is being created

   * @extension: 9p2000.u extension string to support devices, etc.

   * @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;

  	p9_debug(P9_DEBUG_VFS, "name %s
  ", dentry->d_name.name);

  	err = 0;
  	ofid = NULL;
  	fid = NULL;
  	name = (char *) dentry->d_name.name;

  	dfid = v9fs_fid_lookup(dentry->d_parent);

  	if (IS_ERR(dfid)) {

  		err = PTR_ERR(dfid);

  		p9_debug(P9_DEBUG_VFS, "fid lookup failed %d
  ", err);

  		return ERR_PTR(err);

  	}

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

  		p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d
  ", err);

  		return ERR_PTR(err);

  	}

  	err = p9_client_fcreate(ofid, name, perm, mode, extension);

  	if (err < 0) {

  		p9_debug(P9_DEBUG_VFS, "p9_client_fcreate failed %d
  ", err);

  		goto error;

  	}

  	if (!(perm & P9_DMLINK)) {
  		/* now walk from the parent so we can get unopened fid */
  		fid = p9_client_walk(dfid, 1, &name, 1);
  		if (IS_ERR(fid)) {
  			err = PTR_ERR(fid);
  			p9_debug(P9_DEBUG_VFS,
  				   "p9_client_walk failed %d
  ", err);
  			fid = NULL;
  			goto error;
  		}
  		/*
  		 * instantiate inode and assign the unopened fid to the dentry
  		 */
  		inode = v9fs_get_new_inode_from_fid(v9ses, fid, dir->i_sb);
  		if (IS_ERR(inode)) {
  			err = PTR_ERR(inode);
  			p9_debug(P9_DEBUG_VFS,
  				   "inode creation failed %d
  ", err);
  			goto error;
  		}
  		err = v9fs_fid_add(dentry, fid);
  		if (err < 0)
  			goto error;
  		d_instantiate(dentry, inode);

  	}

  	return ofid;

  error:

  	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, umode_t mode,

  		struct nameidata *nd)
  {
  	int err;
  	u32 perm;
  	int flags;

  	struct file *filp;
  	struct v9fs_inode *v9inode;

  	struct v9fs_session_info *v9ses;

  	struct p9_fid *fid, *inode_fid;

  
  	err = 0;
  	fid = NULL;
  	v9ses = v9fs_inode2v9ses(dir);
  	perm = unixmode2p9mode(v9ses, mode);

  	if (nd)

  		flags = nd->intent.open.flags;

  	else
  		flags = O_RDWR;
  
  	fid = v9fs_create(v9ses, dir, dentry, NULL, perm,

  				v9fs_uflags2omode(flags,
  						v9fs_proto_dotu(v9ses)));

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

  	v9fs_invalidate_inode_attr(dir);

  	/* if we are opening a file, assign the open fid to the file */

  	if (nd) {

  		v9inode = V9FS_I(dentry->d_inode);

  		mutex_lock(&v9inode->v_mutex);

  		if (v9ses->cache && !v9inode->writeback_fid &&
  		    ((flags & O_ACCMODE) != O_RDONLY)) {

  			/*

  			 * clone a fid and add it to writeback_fid

  			 * we do it during open time instead of
  			 * page dirty time via write_begin/page_mkwrite
  			 * because we want write after unlink usecase
  			 * to work.
  			 */
  			inode_fid = v9fs_writeback_fid(dentry);
  			if (IS_ERR(inode_fid)) {
  				err = PTR_ERR(inode_fid);

  				mutex_unlock(&v9inode->v_mutex);

  				goto error;
  			}

  			v9inode->writeback_fid = (void *) inode_fid;

  		}

  		mutex_unlock(&v9inode->v_mutex);

  		filp = lookup_instantiate_filp(nd, dentry, generic_file_open);

  		if (IS_ERR(filp)) {

  			err = PTR_ERR(filp);
  			goto error;

  		}

  		filp->private_data = fid;

  #ifdef CONFIG_9P_FSCACHE
  		if (v9ses->cache)
  			v9fs_cache_inode_set_cookie(dentry->d_inode, filp);
  #endif

  	} 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, umode_t mode)

  {

  	int err;

  	u32 perm;

  	struct p9_fid *fid;

  	struct v9fs_session_info *v9ses;

  	p9_debug(P9_DEBUG_VFS, "name %s
  ", 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;

  	} else {

  		inc_nlink(dir);

  		v9fs_invalidate_inode_attr(dir);
  	}

  	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
   *
   */

  struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,

  				      struct nameidata *nameidata)
  {

  	struct dentry *res;

  	struct super_block *sb;
  	struct v9fs_session_info *v9ses;

  	struct p9_fid *dfid, *fid;

  	struct inode *inode;

  	char *name;

  	int result = 0;

  	p9_debug(P9_DEBUG_VFS, "dir: %p dentry: (%s) %p nameidata: %p
  ",
  		 dir, dentry->d_name.name, dentry, nameidata);

  	if (dentry->d_name.len > NAME_MAX)
  		return ERR_PTR(-ENAMETOOLONG);

  	sb = dir->i_sb;
  	v9ses = v9fs_inode2v9ses(dir);

  	/* We can walk d_parent because we hold the dir->i_mutex */

  	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) {

  			inode = NULL;
  			goto inst_out;

  		}

  		return ERR_PTR(result);

  	}

  	/*
  	 * Make sure we don't use a wrong inode due to parallel
  	 * unlink. For cached mode create calls request for new
  	 * inode. But with cache disabled, lookup should do this.
  	 */
  	if (v9ses->cache)
  		inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb);
  	else
  		inode = v9fs_get_new_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_iput;

  inst_out:

  	/*
  	 * If we had a rename on the server and a parallel lookup
  	 * for the new name, then make sure we instantiate with
  	 * the new name. ie look up for a/b, while on server somebody
  	 * moved b under k and client parallely did a lookup for
  	 * k/b.
  	 */
  	res = d_materialise_unique(dentry, inode);
  	if (!IS_ERR(res))
  		return res;
  	result = PTR_ERR(res);

  error_iput:
  	iput(inode);

  error:

  	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

   *
   */

  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

   *
   */

  int v9fs_vfs_rmdir(struct inode *i, struct dentry *d)

  {

  	return v9fs_remove(i, d, AT_REMOVEDIR);

  }
  
  /**
   * 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
   *
   */

  int

  v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
  		struct inode *new_dir, struct dentry *new_dentry)
  {

  	int retval;

  	struct inode *old_inode;

  	struct inode *new_inode;

  	struct v9fs_session_info *v9ses;
  	struct p9_fid *oldfid;
  	struct p9_fid *olddirfid;
  	struct p9_fid *newdirfid;
  	struct p9_wstat wstat;

  	p9_debug(P9_DEBUG_VFS, "
  ");

  	retval = 0;
  	old_inode = old_dentry->d_inode;

  	new_inode = new_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;

  	}

  	down_write(&v9ses->rename_sem);

  	if (v9fs_proto_dotl(v9ses)) {

  		retval = p9_client_renameat(olddirfid, old_dentry->d_name.name,
  					    newdirfid, new_dentry->d_name.name);
  		if (retval == -EOPNOTSUPP)
  			retval = p9_client_rename(oldfid, newdirfid,
  						  new_dentry->d_name.name);
  		if (retval != -EOPNOTSUPP)

  			goto clunk_newdir;
  	}

  	if (old_dentry->d_parent != new_dentry->d_parent) {
  		/*
  		 * 9P .u can only handle file rename in the same directory
  		 */

  		p9_debug(P9_DEBUG_ERROR, "old dir and new dir are different
  ");

  		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:

  	if (!retval) {
  		if (new_inode) {
  			if (S_ISDIR(new_inode->i_mode))
  				clear_nlink(new_inode);
  			else
  				drop_nlink(new_inode);
  		}
  		if (S_ISDIR(old_inode->i_mode)) {
  			if (!new_inode)
  				inc_nlink(new_dir);
  			drop_nlink(old_dir);
  		}

  		v9fs_invalidate_inode_attr(old_inode);

  		v9fs_invalidate_inode_attr(old_dir);
  		v9fs_invalidate_inode_attr(new_dir);

  		/* successful rename */
  		d_move(old_dentry, new_dentry);

  	}

  	up_write(&v9ses->rename_sem);

  	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_wstat *st;

  	p9_debug(P9_DEBUG_VFS, "dentry: %p
  ", dentry);

  	err = -EPERM;

  	v9ses = v9fs_dentry2v9ses(dentry);

  	if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE) {
  		generic_fillattr(dentry->d_inode, stat);
  		return 0;
  	}

  	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);

  	p9stat_free(st);

  	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_debug(P9_DEBUG_VFS, "
  ");

  	retval = inode_change_ok(dentry->d_inode, iattr);
  	if (retval)
  		return retval;

  	retval = -EPERM;

  	v9ses = v9fs_dentry2v9ses(dentry);

  	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_proto_dotu(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;

  	}

  	/* Write all dirty data */
  	if (S_ISREG(dentry->d_inode->i_mode))
  		filemap_write_and_wait(dentry->d_inode->i_mapping);

  	retval = p9_client_wstat(fid, &wstat);
  	if (retval < 0)
  		return retval;

  
  	if ((iattr->ia_valid & ATTR_SIZE) &&
  	    iattr->ia_size != i_size_read(dentry->d_inode))
  		truncate_setsize(dentry->d_inode, iattr->ia_size);

  	v9fs_invalidate_inode_attr(dentry->d_inode);

  	setattr_copy(dentry->d_inode, iattr);
  	mark_inode_dirty(dentry->d_inode);
  	return 0;

  }
  
  /**

   * 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_wstat *stat, struct inode *inode,

  	struct super_block *sb)

  {

  	umode_t mode;

  	char ext[32];

  	char tag_name[14];
  	unsigned int i_nlink;

  	struct v9fs_session_info *v9ses = sb->s_fs_info;

  	struct v9fs_inode *v9inode = V9FS_I(inode);

  	set_nlink(inode, 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_proto_dotu(v9ses)) {

  		inode->i_uid = stat->n_uid;
  		inode->i_gid = stat->n_gid;

  	}

  	if ((S_ISREG(inode->i_mode)) || (S_ISDIR(inode->i_mode))) {
  		if (v9fs_proto_dotu(v9ses) && (stat->extension[0] != '\0')) {
  			/*
  			 * Hadlink support got added later to
  			 * to the .u extension. So there can be
  			 * server out there that doesn't support
  			 * this even with .u extension. So check
  			 * for non NULL stat->extension
  			 */
  			strncpy(ext, stat->extension, sizeof(ext));
  			/* HARDLINKCOUNT %u */
  			sscanf(ext, "%13s %u", tag_name, &i_nlink);
  			if (!strncmp(tag_name, "HARDLINKCOUNT", 13))

  				set_nlink(inode, i_nlink);

  		}
  	}

  	mode = p9mode2perm(v9ses, stat);

  	mode |= inode->i_mode & ~S_IALLUGO;
  	inode->i_mode = mode;

  	i_size_write(inode, stat->length);

  	/* not real number of blocks, but 512 byte ones ... */

  	inode->i_blocks = (i_size_read(inode) + 512 - 1) >> 9;

  	v9inode->cache_validity &= ~V9FS_INO_INVALID_ATTR;

  }
  
  /**
   * 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_wstat *st;

  	p9_debug(P9_DEBUG_VFS, " %s
  ", dentry->d_name.name);

  	retval = -EPERM;

  	v9ses = v9fs_dentry2v9ses(dentry);

  	fid = v9fs_fid_lookup(dentry);

  	if (IS_ERR(fid))

  		return PTR_ERR(fid);

  	if (!v9fs_proto_dotu(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 */

  	strncpy(buffer, st->extension, buflen);

  	p9_debug(P9_DEBUG_VFS, "%s -> %s (%s)
  ",
  		 dentry->d_name.name, st->extension, buffer);

  	retval = strnlen(buffer, buflen);

  done:

  	p9stat_free(st);

  	kfree(st);

  	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_debug(P9_DEBUG_VFS, "%s
  ", 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[min(len, PATH_MAX-1)] = 0;

  	}
  	nd_set_link(nd, link);
  
  	return NULL;
  }
  
  /**
   * v9fs_vfs_put_link - release a symlink path
   * @dentry: dentry for symlink
   * @nd: nameidata

   * @p: unused

   *
   */

  void

  v9fs_vfs_put_link(struct dentry *dentry, struct nameidata *nd, void *p)

  {
  	char *s = nd_get_link(nd);

  	p9_debug(P9_DEBUG_VFS, " %s %s
  ",
  		 dentry->d_name.name, IS_ERR(s) ? "<error>" : 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,

  	u32 perm, const char *extension)

  {

  	struct p9_fid *fid;

  	struct v9fs_session_info *v9ses;

  	v9ses = v9fs_inode2v9ses(dir);

  	if (!v9fs_proto_dotu(v9ses)) {

  		p9_debug(P9_DEBUG_ERROR, "not extended
  ");

  		return -EPERM;

  	}

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

  	v9fs_invalidate_inode_attr(dir);

  	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_debug(P9_DEBUG_VFS, " %lu,%s,%s
  ",
  		 dir->i_ino, dentry->d_name.name, symname);

  	return v9fs_vfs_mkspecial(dir, dentry, P9_DMSYMLINK, 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;

  	char *name;

  	struct p9_fid *oldfid;

  	p9_debug(P9_DEBUG_VFS, " %lu,%s,%s
  ",
  		 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
  ", oldfid->fid);

  	retval = v9fs_vfs_mkspecial(dir, dentry, P9_DMLINK, name);

  	__putname(name);

  	if (!retval) {
  		v9fs_refresh_inode(oldfid, old_dentry->d_inode);

  		v9fs_invalidate_inode_attr(dir);

  	}

  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, umode_t mode, dev_t rdev)

  {

  	struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);

  	int retval;
  	char *name;

  	u32 perm;

  	p9_debug(P9_DEBUG_VFS, " %lu,%s mode: %hx MAJOR: %u MINOR: %u
  ",

  		 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 if (S_ISSOCK(mode))
  		*name = 0;