/*
   * namei.c - NTFS kernel directory inode operations. Part of the Linux-NTFS
   *	     project.
   *
   * Copyright (c) 2001-2006 Anton Altaparmakov
   *
   * This program/include file is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as published
   * by the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program/include file 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 (in the main directory of the Linux-NTFS
   * distribution in the file COPYING); if not, write to the Free Software
   * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  #include <linux/dcache.h>
  #include <linux/exportfs.h>
  #include <linux/security.h>
  #include <linux/slab.h>
  
  #include "attrib.h"
  #include "debug.h"
  #include "dir.h"
  #include "mft.h"
  #include "ntfs.h"
  
  /**
   * ntfs_lookup - find the inode represented by a dentry in a directory inode
   * @dir_ino:	directory inode in which to look for the inode
   * @dent:	dentry representing the inode to look for
   * @nd:		lookup nameidata
   *
   * In short, ntfs_lookup() looks for the inode represented by the dentry @dent
   * in the directory inode @dir_ino and if found attaches the inode to the
   * dentry @dent.
   *
   * In more detail, the dentry @dent specifies which inode to look for by
   * supplying the name of the inode in @dent->d_name.name. ntfs_lookup()
   * converts the name to Unicode and walks the contents of the directory inode
   * @dir_ino looking for the converted Unicode name. If the name is found in the
   * directory, the corresponding inode is loaded by calling ntfs_iget() on its
   * inode number and the inode is associated with the dentry @dent via a call to
   * d_splice_alias().
   *
   * If the name is not found in the directory, a NULL inode is inserted into the
   * dentry @dent via a call to d_add(). The dentry is then termed a negative
   * dentry.
   *
   * Only if an actual error occurs, do we return an error via ERR_PTR().
   *
   * In order to handle the case insensitivity issues of NTFS with regards to the
   * dcache and the dcache requiring only one dentry per directory, we deal with
   * dentry aliases that only differ in case in ->ntfs_lookup() while maintaining
   * a case sensitive dcache. This means that we get the full benefit of dcache
   * speed when the file/directory is looked up with the same case as returned by
   * ->ntfs_readdir() but that a lookup for any other case (or for the short file
   * name) will not find anything in dcache and will enter ->ntfs_lookup()
   * instead, where we search the directory for a fully matching file name
   * (including case) and if that is not found, we search for a file name that
   * matches with different case and if that has non-POSIX semantics we return
   * that. We actually do only one search (case sensitive) and keep tabs on
   * whether we have found a case insensitive match in the process.
   *
   * To simplify matters for us, we do not treat the short vs long filenames as
   * two hard links but instead if the lookup matches a short filename, we
   * return the dentry for the corresponding long filename instead.
   *
   * There are three cases we need to distinguish here:
   *
   * 1) @dent perfectly matches (i.e. including case) a directory entry with a
   *    file name in the WIN32 or POSIX namespaces. In this case
   *    ntfs_lookup_inode_by_name() will return with name set to NULL and we
   *    just d_splice_alias() @dent.
   * 2) @dent matches (not including case) a directory entry with a file name in
   *    the WIN32 namespace. In this case ntfs_lookup_inode_by_name() will return
   *    with name set to point to a kmalloc()ed ntfs_name structure containing
   *    the properly cased little endian Unicode name. We convert the name to the
   *    current NLS code page, search if a dentry with this name already exists
   *    and if so return that instead of @dent.  At this point things are
   *    complicated by the possibility of 'disconnected' dentries due to NFS
   *    which we deal with appropriately (see the code comments).  The VFS will
   *    then destroy the old @dent and use the one we returned.  If a dentry is
   *    not found, we allocate a new one, d_splice_alias() it, and return it as
   *    above.
   * 3) @dent matches either perfectly or not (i.e. we don't care about case) a
   *    directory entry with a file name in the DOS namespace. In this case
   *    ntfs_lookup_inode_by_name() will return with name set to point to a
   *    kmalloc()ed ntfs_name structure containing the mft reference (cpu endian)
   *    of the inode. We use the mft reference to read the inode and to find the
   *    file name in the WIN32 namespace corresponding to the matched short file
   *    name. We then convert the name to the current NLS code page, and proceed
   *    searching for a dentry with this name, etc, as in case 2), above.
   *
   * Locking: Caller must hold i_mutex on the directory.
   */
  static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
  		unsigned int flags)
  {
  	ntfs_volume *vol = NTFS_SB(dir_ino->i_sb);
  	struct inode *dent_inode;
  	ntfschar *uname;
  	ntfs_name *name = NULL;
  	MFT_REF mref;
  	unsigned long dent_ino;
  	int uname_len;
  
  	ntfs_debug("Looking up %s in directory inode 0x%lx.",
  			dent->d_name.name, dir_ino->i_ino);
  	/* Convert the name of the dentry to Unicode. */
  	uname_len = ntfs_nlstoucs(vol, dent->d_name.name, dent->d_name.len,
  			&uname);
  	if (uname_len < 0) {
  		if (uname_len != -ENAMETOOLONG)
  			ntfs_error(vol->sb, "Failed to convert name to "
  					"Unicode.");
  		return ERR_PTR(uname_len);
  	}
  	mref = ntfs_lookup_inode_by_name(NTFS_I(dir_ino), uname, uname_len,
  			&name);
  	kmem_cache_free(ntfs_name_cache, uname);
  	if (!IS_ERR_MREF(mref)) {
  		dent_ino = MREF(mref);
  		ntfs_debug("Found inode 0x%lx. Calling ntfs_iget.", dent_ino);
  		dent_inode = ntfs_iget(vol->sb, dent_ino);
  		if (likely(!IS_ERR(dent_inode))) {
  			/* Consistency check. */
  			if (is_bad_inode(dent_inode) || MSEQNO(mref) ==
  					NTFS_I(dent_inode)->seq_no ||
  					dent_ino == FILE_MFT) {
  				/* Perfect WIN32/POSIX match. -- Case 1. */
  				if (!name) {
  					ntfs_debug("Done.  (Case 1.)");
  					return d_splice_alias(dent_inode, dent);
  				}
  				/*
  				 * We are too indented.  Handle imperfect
  				 * matches and short file names further below.
  				 */
  				goto handle_name;
  			}
  			ntfs_error(vol->sb, "Found stale reference to inode "
  					"0x%lx (reference sequence number = "
  					"0x%x, inode sequence number = 0x%x), "
  					"returning -EIO. Run chkdsk.",
  					dent_ino, MSEQNO(mref),
  					NTFS_I(dent_inode)->seq_no);
  			iput(dent_inode);
  			dent_inode = ERR_PTR(-EIO);
  		} else
  			ntfs_error(vol->sb, "ntfs_iget(0x%lx) failed with "
  					"error code %li.", dent_ino,
  					PTR_ERR(dent_inode));
  		kfree(name);
  		/* Return the error code. */
  		return (struct dentry *)dent_inode;
  	}
  	/* It is guaranteed that @name is no longer allocated at this point. */
  	if (MREF_ERR(mref) == -ENOENT) {
  		ntfs_debug("Entry was not found, adding negative dentry.");
  		/* The dcache will handle negative entries. */
  		d_add(dent, NULL);
  		ntfs_debug("Done.");
  		return NULL;
  	}
  	ntfs_error(vol->sb, "ntfs_lookup_ino_by_name() failed with error "
  			"code %i.", -MREF_ERR(mref));
  	return ERR_PTR(MREF_ERR(mref));
  	// TODO: Consider moving this lot to a separate function! (AIA)
  handle_name:
     {
  	MFT_RECORD *m;
  	ntfs_attr_search_ctx *ctx;
  	ntfs_inode *ni = NTFS_I(dent_inode);
  	int err;
  	struct qstr nls_name;
  
  	nls_name.name = NULL;
  	if (name->type != FILE_NAME_DOS) {			/* Case 2. */
  		ntfs_debug("Case 2.");
  		nls_name.len = (unsigned)ntfs_ucstonls(vol,
  				(ntfschar*)&name->name, name->len,
  				(unsigned char**)&nls_name.name, 0);
  		kfree(name);
  	} else /* if (name->type == FILE_NAME_DOS) */ {		/* Case 3. */
  		FILE_NAME_ATTR *fn;
  
  		ntfs_debug("Case 3.");
  		kfree(name);
  
  		/* Find the WIN32 name corresponding to the matched DOS name. */
  		ni = NTFS_I(dent_inode);
  		m = map_mft_record(ni);
  		if (IS_ERR(m)) {
  			err = PTR_ERR(m);
  			m = NULL;
  			ctx = NULL;
  			goto err_out;
  		}
  		ctx = ntfs_attr_get_search_ctx(ni, m);
  		if (unlikely(!ctx)) {
  			err = -ENOMEM;
  			goto err_out;
  		}
  		do {
  			ATTR_RECORD *a;
  			u32 val_len;
  
  			err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, 0, 0,
  					NULL, 0, ctx);
  			if (unlikely(err)) {
  				ntfs_error(vol->sb, "Inode corrupt: No WIN32 "
  						"namespace counterpart to DOS "
  						"file name. Run chkdsk.");
  				if (err == -ENOENT)
  					err = -EIO;
  				goto err_out;
  			}
  			/* Consistency checks. */
  			a = ctx->attr;
  			if (a->non_resident || a->flags)
  				goto eio_err_out;
  			val_len = le32_to_cpu(a->data.resident.value_length);
  			if (le16_to_cpu(a->data.resident.value_offset) +
  					val_len > le32_to_cpu(a->length))
  				goto eio_err_out;
  			fn = (FILE_NAME_ATTR*)((u8*)ctx->attr + le16_to_cpu(
  					ctx->attr->data.resident.value_offset));
  			if ((u32)(fn->file_name_length * sizeof(ntfschar) +
  					sizeof(FILE_NAME_ATTR)) > val_len)
  				goto eio_err_out;
  		} while (fn->file_name_type != FILE_NAME_WIN32);
  
  		/* Convert the found WIN32 name to current NLS code page. */
  		nls_name.len = (unsigned)ntfs_ucstonls(vol,
  				(ntfschar*)&fn->file_name, fn->file_name_length,
  				(unsigned char**)&nls_name.name, 0);
  
  		ntfs_attr_put_search_ctx(ctx);
  		unmap_mft_record(ni);
  	}
  	m = NULL;
  	ctx = NULL;
  
  	/* Check if a conversion error occurred. */
  	if ((signed)nls_name.len < 0) {
  		err = (signed)nls_name.len;
  		goto err_out;
  	}
  	nls_name.hash = full_name_hash(nls_name.name, nls_name.len);
  
  	dent = d_add_ci(dent, dent_inode, &nls_name);
  	kfree(nls_name.name);
  	return dent;
  
  eio_err_out:
  	ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
  	err = -EIO;
  err_out:
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(ni);
  	iput(dent_inode);
  	ntfs_error(vol->sb, "Failed, returning error code %i.", err);
  	return ERR_PTR(err);
     }
  }
  
  /**
   * Inode operations for directories.
   */
  const struct inode_operations ntfs_dir_inode_ops = {
  	.lookup	= ntfs_lookup,	/* VFS: Lookup directory. */
  };
  
  /**
   * ntfs_get_parent - find the dentry of the parent of a given directory dentry
   * @child_dent:		dentry of the directory whose parent directory to find
   *
   * Find the dentry for the parent directory of the directory specified by the
   * dentry @child_dent.  This function is called from
   * fs/exportfs/expfs.c::find_exported_dentry() which in turn is called from the
   * default ->decode_fh() which is export_decode_fh() in the same file.
   *
   * The code is based on the ext3 ->get_parent() implementation found in
   * fs/ext3/namei.c::ext3_get_parent().
   *
   * Note: ntfs_get_parent() is called with @child_dent->d_inode->i_mutex down.
   *
   * Return the dentry of the parent directory on success or the error code on
   * error (IS_ERR() is true).
   */
  static struct dentry *ntfs_get_parent(struct dentry *child_dent)
  {
  	struct inode *vi = child_dent->d_inode;
  	ntfs_inode *ni = NTFS_I(vi);
  	MFT_RECORD *mrec;
  	ntfs_attr_search_ctx *ctx;
  	ATTR_RECORD *attr;
  	FILE_NAME_ATTR *fn;
  	unsigned long parent_ino;
  	int err;
  
  	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
  	/* Get the mft record of the inode belonging to the child dentry. */
  	mrec = map_mft_record(ni);
  	if (IS_ERR(mrec))
  		return (struct dentry *)mrec;
  	/* Find the first file name attribute in the mft record. */
  	ctx = ntfs_attr_get_search_ctx(ni, mrec);
  	if (unlikely(!ctx)) {
  		unmap_mft_record(ni);
  		return ERR_PTR(-ENOMEM);
  	}
  try_next:
  	err = ntfs_attr_lookup(AT_FILE_NAME, NULL, 0, CASE_SENSITIVE, 0, NULL,
  			0, ctx);
  	if (unlikely(err)) {
  		ntfs_attr_put_search_ctx(ctx);
  		unmap_mft_record(ni);
  		if (err == -ENOENT)
  			ntfs_error(vi->i_sb, "Inode 0x%lx does not have a "
  					"file name attribute.  Run chkdsk.",
  					vi->i_ino);
  		return ERR_PTR(err);
  	}
  	attr = ctx->attr;
  	if (unlikely(attr->non_resident))
  		goto try_next;
  	fn = (FILE_NAME_ATTR *)((u8 *)attr +
  			le16_to_cpu(attr->data.resident.value_offset));
  	if (unlikely((u8 *)fn + le32_to_cpu(attr->data.resident.value_length) >
  			(u8*)attr + le32_to_cpu(attr->length)))
  		goto try_next;
  	/* Get the inode number of the parent directory. */
  	parent_ino = MREF_LE(fn->parent_directory);
  	/* Release the search context and the mft record of the child. */
  	ntfs_attr_put_search_ctx(ctx);
  	unmap_mft_record(ni);
  
  	return d_obtain_alias(ntfs_iget(vi->i_sb, parent_ino));
  }
  
  static struct inode *ntfs_nfs_get_inode(struct super_block *sb,
  		u64 ino, u32 generation)
  {
  	struct inode *inode;
  
  	inode = ntfs_iget(sb, ino);
  	if (!IS_ERR(inode)) {
  		if (is_bad_inode(inode) || inode->i_generation != generation) {
  			iput(inode);
  			inode = ERR_PTR(-ESTALE);
  		}
  	}
  
  	return inode;
  }
  
  static struct dentry *ntfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
  		int fh_len, int fh_type)
  {
  	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
  				    ntfs_nfs_get_inode);
  }
  
  static struct dentry *ntfs_fh_to_parent(struct super_block *sb, struct fid *fid,
  		int fh_len, int fh_type)
  {
  	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
  				    ntfs_nfs_get_inode);
  }
  
  /**
   * Export operations allowing NFS exporting of mounted NTFS partitions.
   *
   * We use the default ->encode_fh() for now.  Note that they
   * use 32 bits to store the inode number which is an unsigned long so on 64-bit
   * architectures is usually 64 bits so it would all fail horribly on huge
   * volumes.  I guess we need to define our own encode and decode fh functions
   * that store 64-bit inode numbers at some point but for now we will ignore the
   * problem...
   *
   * We also use the default ->get_name() helper (used by ->decode_fh() via
   * fs/exportfs/expfs.c::find_exported_dentry()) as that is completely fs
   * independent.
   *
   * The default ->get_parent() just returns -EACCES so we have to provide our
   * own and the default ->get_dentry() is incompatible with NTFS due to not
   * allowing the inode number 0 which is used in NTFS for the system file $MFT
   * and due to using iget() whereas NTFS needs ntfs_iget().
   */
  const struct export_operations ntfs_export_ops = {
  	.get_parent	= ntfs_get_parent,	/* Find the parent of a given
  						   directory. */
  	.fh_to_dentry	= ntfs_fh_to_dentry,
  	.fh_to_parent	= ntfs_fh_to_parent,
  };