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FAT file systems do not use inodes, instead all file meta-information is stored in directory entries. FAT12 and FAT16 use a fixed size area for root directories, with typically 512 entries of 32 bytes each (for a total of 16 KB) on hard disk formats. The file system data is stored in clusters of typically 512 to 4096 bytes, depending on the size of the file system. The current code uses the offset of a DOS 8.3 style directory entry as a pseudo-inode, which leads to inode values of 0 to 16368 for typical root directories with 512 entries. Sub-directories use 2 cluster length plus the byte offset of the directory entry in the data area for the pseudo-inode, which may be as low as 1024 in case of 512 byte clusters. A sub-directory in cluster 2 and with 512 byte clusters will therefore lead to a re-use of inode 1024 when there are at least 32 DOS 8.3 style filenames in the root directory (or 11 14-character Windows long file names, each of which takes up 3 directory entries). FAT32 file systems are not affected by this issue and FAT12/FAT16 file systems with larger cluster sizes are unlikely to have as many directory entries in the root directory as are required to cause the collision. This commit leads to inode numbers that are guaranteed to not collide for all valid FAT12 and FAT16 file system parameters. It does also provide a small speed-up due to more efficient use of the vnode cache. Approved by: mckusick MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D43978
299 lines
12 KiB
C
299 lines
12 KiB
C
/* $NetBSD: denode.h,v 1.25 1997/11/17 15:36:28 ws Exp $ */
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/*-
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* SPDX-License-Identifier: BSD-4-Clause
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*
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* Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
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* Copyright (C) 1994, 1995, 1997 TooLs GmbH.
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* All rights reserved.
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* Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by TooLs GmbH.
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* 4. The name of TooLs GmbH may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*-
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* Written by Paul Popelka (paulp@uts.amdahl.com)
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*
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* You can do anything you want with this software, just don't say you wrote
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* it, and don't remove this notice.
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*
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* This software is provided "as is".
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*
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* The author supplies this software to be publicly redistributed on the
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* understanding that the author is not responsible for the correct
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* functioning of this software in any circumstances and is not liable for
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* any damages caused by this software.
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*
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* October 1992
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*/
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#ifndef _FS_MSDOSFS_DENODE_H_
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#define _FS_MSDOSFS_DENODE_H_
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/*
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* This is the pc filesystem specific portion of the vnode structure.
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*
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* To describe a file uniquely the de_dirclust, de_diroffset, and
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* de_StartCluster fields are used.
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*
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* de_dirclust contains the cluster number of the directory cluster
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* containing the entry for a file or directory.
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* de_diroffset is the index into the cluster for the entry describing
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* a file or directory.
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* de_StartCluster is the number of the first cluster of the file or directory.
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*
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* Now to describe the quirks of the pc filesystem.
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* - Clusters 0 and 1 are reserved.
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* - The first allocatable cluster is 2.
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* - The root directory is of fixed size and all blocks that make it up
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* are contiguous.
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* - Cluster 0 refers to the root directory when it is found in the
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* startcluster field of a directory entry that points to another directory.
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* - Cluster 0 implies a 0 length file when found in the start cluster field
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* of a directory entry that points to a file.
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* - You can't use the cluster number 0 to derive the address of the root
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* directory.
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* - Multiple directory entries can point to a directory. The entry in the
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* parent directory points to a child directory. Any directories in the
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* child directory contain a ".." entry that points back to the parent.
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* The child directory itself contains a "." entry that points to itself.
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* - The root directory does not contain a "." or ".." entry.
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* - Directory entries for directories are never changed once they are created
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* (except when removed). The size stays 0, and the last modification time
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* is never changed. This is because so many directory entries can point to
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* the physical clusters that make up a directory. It would lead to an
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* update nightmare.
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* - The length field in a directory entry pointing to a directory contains 0
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* (always). The only way to find the end of a directory is to follow the
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* cluster chain until the "last cluster" marker is found.
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*
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* My extensions to make this house of cards work. These apply only to the in
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* memory copy of the directory entry.
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* - A reference count for each denode will be kept since dos doesn't keep such
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* things.
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*/
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/*
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* Internal pseudo-offset for (nonexistent) directory entry for the root
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* dir in the root dir
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*/
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#define MSDOSFSROOT_OFS 0x1fffffff
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/*
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* The FAT cache structure. fc_fsrcn is the filesystem relative cluster
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* number that corresponds to the file relative cluster number in this
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* structure (fc_frcn).
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*/
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struct fatcache {
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u_long fc_frcn; /* file relative cluster number */
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u_long fc_fsrcn; /* filesystem relative cluster number */
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};
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/*
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* The FAT entry cache as it stands helps make extending files a "quick"
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* operation by avoiding having to scan the FAT to discover the last
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* cluster of the file. The cache also helps sequential reads by
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* remembering the last cluster read from the file. This also prevents us
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* from having to rescan the FAT to find the next cluster to read. This
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* cache is probably pretty worthless if a file is opened by multiple
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* processes.
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*/
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#define FC_SIZE 3 /* number of entries in the cache */
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#define FC_LASTMAP 0 /* entry the last call to pcbmap() resolved
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* to */
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#define FC_LASTFC 1 /* entry for the last cluster in the file */
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#define FC_NEXTTOLASTFC 2 /* entry for a close to the last cluster in
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* the file */
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#define FCE_EMPTY 0xffffffff /* doesn't represent an actual cluster # */
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/*
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* Set a slot in the FAT cache.
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*/
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#define fc_setcache(dep, slot, frcn, fsrcn) \
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(dep)->de_fc[(slot)].fc_frcn = (frcn); \
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(dep)->de_fc[(slot)].fc_fsrcn = (fsrcn);
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/*
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* This is the in memory variant of a dos directory entry. It is usually
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* contained within a vnode.
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*/
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struct denode {
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struct vnode *de_vnode; /* addr of vnode we are part of */
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struct vn_clusterw de_clusterw; /* buffer clustering information */
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u_long de_flag; /* flag bits */
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u_long de_dirclust; /* cluster of the directory file containing this entry */
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u_long de_diroffset; /* offset of this entry in the directory cluster */
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u_long de_fndoffset; /* offset of found dir entry */
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int de_fndcnt; /* number of slots before de_fndoffset */
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long de_refcnt; /* reference count */
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struct msdosfsmount *de_pmp; /* addr of our mount struct */
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u_char de_Name[12]; /* name, from DOS directory entry */
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u_char de_Attributes; /* attributes, from directory entry */
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u_char de_LowerCase; /* NT VFAT lower case flags */
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u_char de_CHun; /* Hundredth of second of CTime*/
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u_short de_CTime; /* creation time */
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u_short de_CDate; /* creation date */
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u_short de_ADate; /* access date */
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u_short de_MTime; /* modification time */
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u_short de_MDate; /* modification date */
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u_long de_StartCluster; /* starting cluster of file */
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u_long de_FileSize; /* size of file in bytes */
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struct fatcache de_fc[FC_SIZE]; /* FAT cache */
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u_quad_t de_modrev; /* Revision level for lease. */
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uint64_t de_inode; /* Inode number (really index of DOS style direntry) */
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};
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/*
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* Values for the de_flag field of the denode.
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*/
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#define DE_UPDATE 0x0004 /* Modification time update request */
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#define DE_CREATE 0x0008 /* Creation time update */
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#define DE_ACCESS 0x0010 /* Access time update */
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#define DE_MODIFIED 0x0020 /* Denode has been modified */
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/* Maximum size of a file on a FAT filesystem */
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#define MSDOSFS_FILESIZE_MAX 0xFFFFFFFFLL
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/*
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* Transfer directory entries between internal and external form.
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* dep is a struct denode * (internal form),
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* dp is a struct direntry * (external form).
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*/
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#define DE_INTERNALIZE32(dep, dp) \
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((dep)->de_StartCluster |= getushort((dp)->deHighClust) << 16)
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#define DE_INTERNALIZE(dep, dp) \
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(memcpy((dep)->de_Name, (dp)->deName, 11), \
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(dep)->de_Attributes = (dp)->deAttributes, \
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(dep)->de_LowerCase = (dp)->deLowerCase, \
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(dep)->de_CHun = (dp)->deCHundredth, \
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(dep)->de_CTime = getushort((dp)->deCTime), \
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(dep)->de_CDate = getushort((dp)->deCDate), \
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(dep)->de_ADate = getushort((dp)->deADate), \
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(dep)->de_MTime = getushort((dp)->deMTime), \
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(dep)->de_MDate = getushort((dp)->deMDate), \
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(dep)->de_StartCluster = getushort((dp)->deStartCluster), \
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(dep)->de_FileSize = getulong((dp)->deFileSize), \
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(FAT32((dep)->de_pmp) ? DE_INTERNALIZE32((dep), (dp)) : 0))
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#define DE_EXTERNALIZE(dp, dep) \
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(memcpy((dp)->deName, (dep)->de_Name, 11), \
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(dp)->deAttributes = (dep)->de_Attributes, \
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(dp)->deLowerCase = (dep)->de_LowerCase, \
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(dp)->deCHundredth = (dep)->de_CHun, \
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putushort((dp)->deCTime, (dep)->de_CTime), \
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putushort((dp)->deCDate, (dep)->de_CDate), \
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putushort((dp)->deADate, (dep)->de_ADate), \
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putushort((dp)->deMTime, (dep)->de_MTime), \
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putushort((dp)->deMDate, (dep)->de_MDate), \
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putushort((dp)->deStartCluster, (dep)->de_StartCluster), \
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putulong((dp)->deFileSize, \
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((dep)->de_Attributes & ATTR_DIRECTORY) ? 0 : (dep)->de_FileSize), \
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putushort((dp)->deHighClust, (dep)->de_StartCluster >> 16))
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#if defined(_KERNEL) || defined(MAKEFS)
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#define VTODE(vp) ((struct denode *)(vp)->v_data)
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#define DETOV(de) ((de)->de_vnode)
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#define DETOI(pmp, cn, off) \
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((cn) == MSDOSFSROOT \
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? (((uint64_t)(off) >> 5)) \
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: (((((uint64_t)pmp->pm_bpcluster * ((cn) - 2) + (off))) >> 5) \
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+ pmp->pm_RootDirEnts))
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#define DETIMES(dep, acc, mod, cre) do { \
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if ((dep)->de_flag & DE_UPDATE) { \
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(dep)->de_flag |= DE_MODIFIED; \
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timespec2fattime((mod), 0, &(dep)->de_MDate, \
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&(dep)->de_MTime, NULL); \
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(dep)->de_Attributes |= ATTR_ARCHIVE; \
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} \
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if ((dep)->de_pmp->pm_flags & MSDOSFSMNT_NOWIN95) { \
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(dep)->de_flag &= ~(DE_UPDATE | DE_CREATE | DE_ACCESS); \
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break; \
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} \
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if ((dep)->de_flag & DE_ACCESS) { \
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uint16_t adate; \
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\
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timespec2fattime((acc), 0, &adate, NULL, NULL); \
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if (adate != (dep)->de_ADate) { \
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(dep)->de_flag |= DE_MODIFIED; \
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(dep)->de_ADate = adate; \
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} \
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} \
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if ((dep)->de_flag & DE_CREATE) { \
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timespec2fattime((cre), 0, &(dep)->de_CDate, \
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&(dep)->de_CTime, &(dep)->de_CHun); \
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(dep)->de_flag |= DE_MODIFIED; \
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} \
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(dep)->de_flag &= ~(DE_UPDATE | DE_CREATE | DE_ACCESS); \
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} while (0)
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/*
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* This overlays the fid structure (see mount.h)
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*/
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struct defid {
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u_short defid_len; /* length of structure */
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u_short defid_pad; /* force long alignment */
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uint32_t defid_dirclust; /* cluster this dir entry came from */
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uint32_t defid_dirofs; /* offset of entry within the cluster */
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#if 0
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uint32_t defid_gen; /* generation number */
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#endif
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};
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extern struct vop_vector msdosfs_vnodeops;
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#ifdef _KERNEL
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int msdosfs_lookup(struct vop_cachedlookup_args *);
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int msdosfs_inactive(struct vop_inactive_args *);
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int msdosfs_reclaim(struct vop_reclaim_args *);
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int msdosfs_lookup_ino(struct vnode *vdp, struct vnode **vpp,
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struct componentname *cnp, daddr_t *scnp, u_long *blkoffp);
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#endif
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/*
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* Internal service routine prototypes.
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*/
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struct componentname;
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int deget(struct msdosfsmount *, u_long, u_long, int, struct denode **);
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int uniqdosname(struct denode *, struct componentname *, u_char *);
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int readep(struct msdosfsmount *pmp, u_long dirclu, u_long dirofs, struct buf **bpp, struct direntry **epp);
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int readde(struct denode *dep, struct buf **bpp, struct direntry **epp);
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int deextend(struct denode *dep, u_long length, struct ucred *cred);
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int fillinusemap(struct msdosfsmount *pmp);
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void reinsert(struct denode *dep);
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int dosdirempty(struct denode *dep);
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int createde(struct denode *dep, struct denode *ddep, struct denode **depp, struct componentname *cnp);
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int deupdat(struct denode *dep, int waitfor);
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int removede(struct denode *pdep, struct denode *dep);
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int detrunc(struct denode *dep, u_long length, int flags, struct ucred *cred);
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int doscheckpath( struct denode *source, struct denode *target,
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daddr_t *wait_scn);
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#endif /* _KERNEL || MAKEFS */
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#endif /* !_FS_MSDOSFS_DENODE_H_ */
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