/*
 * namei.c - NTFS kernel directory inode operations. Part of the Linux-NTFS
 * 	     project.
 *
 * Copyright (c) 2001,2002 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 "ntfs.h"
#include "dir.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
 *
 * 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_add().
 *
 * If the name is not found in the directory, a NULL inode is inserted into the
 * dentry @dent. 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 maintining
 * 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_add() @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. 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_add() 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.
 */
static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent)
{
	ntfs_volume *vol = NTFS_SB(dir_ino->i_sb);
	struct inode *dent_inode;
	uchar_t *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) {
		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 (MSEQNO(mref) == NTFS_I(dent_inode)->seq_no ||
					dent_ino == FILE_MFT) {
				/* Perfect WIN32/POSIX match. -- Case 1. */
				if (!name) {
					d_add(dent, dent_inode);
					ntfs_debug("Done.");
					return NULL;
				}
				/*
				 * 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));
		if (name)
			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:
   {
	struct dentry *real_dent;
	MFT_RECORD *m;
	attr_search_context *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. */
		nls_name.len = (unsigned)ntfs_ucstonls(vol,
				(uchar_t*)&name->name, name->len,
				(unsigned char**)&nls_name.name,
				name->len * 3 + 1);
		kfree(name);
	} else /* if (name->type == FILE_NAME_DOS) */ {		/* Case 3. */
		FILE_NAME_ATTR *fn;

		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 = get_attr_search_ctx(ni, m);
		if (!ctx) {
			err = -ENOMEM;
			goto err_out;
		}
		do {
			ATTR_RECORD *a;
			u32 val_len;

			if (!lookup_attr(AT_FILE_NAME, NULL, 0, 0, 0, NULL, 0,
					ctx)) {
				ntfs_error(vol->sb, "Inode corrupt: No WIN32 "
						"namespace counterpart to DOS "
						"file name. Run chkdsk.");
				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->_ARA(value_length));
			if (le16_to_cpu(a->_ARA(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->_ARA(value_offset)));
			if ((u32)(fn->file_name_length * sizeof(uchar_t) +
					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,
				(uchar_t*)&fn->file_name, fn->file_name_length,
				(unsigned char**)&nls_name.name,
				fn->file_name_length * 3 + 1);

		put_attr_search_ctx(ctx);
		unmap_mft_record(ni);
	}
	m = NULL;
	ctx = NULL;

	/* Check if a conversion error occured. */
	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);

	/*
	 * Note: No need for dparent_lock as i_sem is held on the parent inode.
	 */

	/* Does a dentry matching the nls_name exist already? */
	real_dent = d_lookup(dent->d_parent, &nls_name);
	/* If not, create it now. */
	if (!real_dent) {
		real_dent = d_alloc(dent->d_parent, &nls_name);
		kfree(nls_name.name);
		if (!real_dent) {
			err = -ENOMEM;
			goto err_out;
		}
		d_add(real_dent, dent_inode);
		return real_dent;
	}
	kfree(nls_name.name);
	/* Matching dentry exists, check if it is negative. */
	if (real_dent->d_inode) {
		BUG_ON(real_dent->d_inode != dent_inode);
		/*
		 * Already have the inode and the dentry attached, decrement
		 * the reference count to balance the ntfs_iget() we did
		 * earlier on.
		 */
		iput(dent_inode);
		return real_dent;
	}
	/* Negative dentry: instantiate it. */
	d_instantiate(real_dent, dent_inode);
	return real_dent;

eio_err_out:
	ntfs_error(vol->sb, "Illegal file name attribute. Run chkdsk.");
	err = -EIO;
err_out:
	if (ctx)
		put_attr_search_ctx(ctx);
	if (m)
		unmap_mft_record(ni);
	iput(dent_inode);
	return ERR_PTR(err);
   }
}

/*
 * Inode operations for directories.
 */
struct inode_operations ntfs_dir_inode_ops = {
	.lookup	= ntfs_lookup,	/* VFS: Lookup directory. */
};