path: root/fs/ntfs/dir.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * NTFS kernel directory operations.
 *
 * Copyright (c) 2001-2007 Anton Altaparmakov
 * Copyright (c) 2002 Richard Russon
 * Copyright (c) 2025 LG Electronics Co., Ltd.
 */

#include <linux/blkdev.h>

#include "dir.h"
#include "mft.h"
#include "ntfs.h"
#include "index.h"
#include "reparse.h"

#include <linux/filelock.h>

/*
 * The little endian Unicode string $I30 as a global constant.
 */
__le16 I30[5] = { cpu_to_le16('$'), cpu_to_le16('I'),
		cpu_to_le16('3'),	cpu_to_le16('0'), 0 };

/*
 * ntfs_lookup_inode_by_name - find an inode in a directory given its name
 * @dir_ni:	ntfs inode of the directory in which to search for the name
 * @uname:	Unicode name for which to search in the directory
 * @uname_len:	length of the name @uname in Unicode characters
 * @res:	return the found file name if necessary (see below)
 *
 * Look for an inode with name @uname in the directory with inode @dir_ni.
 * ntfs_lookup_inode_by_name() walks the contents of the directory looking for
 * the Unicode name. If the name is found in the directory, the corresponding
 * inode number (>= 0) is returned as a mft reference in cpu format, i.e. it
 * is a 64-bit number containing the sequence number.
 *
 * On error, a negative value is returned corresponding to the error code. In
 * particular if the inode is not found -ENOENT is returned. Note that you
 * can't just check the return value for being negative, you have to check the
 * inode number for being negative which you can extract using MREC(return
 * value).
 *
 * Note, @uname_len does not include the (optional) terminating NULL character.
 *
 * Note, we look for a case sensitive match first but we also look for a case
 * insensitive match at the same time. If we find a case insensitive match, we
 * save that for the case that we don't find an exact match, where we return
 * the case insensitive match and setup @res (which we allocate!) with the mft
 * reference, the file name type, length and with a copy of the little endian
 * Unicode file name itself. If we match a file name which is in the DOS name
 * space, we only return the mft reference and file name type in @res.
 * ntfs_lookup() then uses this to find the long file name in the inode itself.
 * This is to avoid polluting the dcache with short file names. We want them to
 * work but we don't care for how quickly one can access them. This also fixes
 * the dcache aliasing issues.
 *
 * Locking:  - Caller must hold i_mutex on the directory.
 *	     - Each page cache page in the index allocation mapping must be
 *	       locked whilst being accessed otherwise we may find a corrupt
 *	       page due to it being under ->writepage at the moment which
 *	       applies the mst protection fixups before writing out and then
 *	       removes them again after the write is complete after which it
 *	       unlocks the page.
 */
u64 ntfs_lookup_inode_by_name(struct ntfs_inode *dir_ni, const __le16 *uname,
		const int uname_len, struct ntfs_name **res)
{
	struct ntfs_volume *vol = dir_ni->vol;
	struct super_block *sb = vol->sb;
	struct inode *ia_vi = NULL;
	struct mft_record *m;
	struct index_root *ir;
	struct index_entry *ie;
	struct index_block *ia;
	u8 *index_end;
	u64 mref;
	struct ntfs_attr_search_ctx *ctx;
	int err, rc;
	s64 vcn, old_vcn;
	struct address_space *ia_mapping;
	struct folio *folio;
	u8 *kaddr = NULL;
	struct ntfs_name *name = NULL;

	/* Get hold of the mft record for the directory. */
	m = map_mft_record(dir_ni);
	if (IS_ERR(m)) {
		ntfs_error(sb, "map_mft_record() failed with error code %ld.",
				-PTR_ERR(m));
		return ERR_MREF(PTR_ERR(m));
	}
	ctx = ntfs_attr_get_search_ctx(dir_ni, m);
	if (unlikely(!ctx)) {
		err = -ENOMEM;
		goto err_out;
	}
	/* Find the index root attribute in the mft record. */
	err = ntfs_attr_lookup(AT_INDEX_ROOT, I30, 4, CASE_SENSITIVE, 0, NULL,
			0, ctx);
	if