Unverified Commit f9881662 authored by Christian Brauner's avatar Christian Brauner
Browse files

Merge patch "sysv: Remove the filesystem" 

This removes the sysv filesystem from the kernel.

* patches from https://lore.kernel.org/r/20250220163940.10155-2-jack@suse.cz:
  sysv: Remove the filesystem

Link: https://lore.kernel.org/r/20250220163940.10155-2-jack@suse.cz


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parents 00dac020 448fa701

Documentation/filesystems/index.rst

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@@ -118,7 +118,6 @@ Documentation for filesystem implementations. 
   spufs/index

   squashfs

   sysfs

   sysv-fs

   tmpfs

   ubifs

   ubifs-authentication

Documentation/filesystems/sysv-fs.rst

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.. SPDX-License-Identifier: GPL-2.0



==================

SystemV Filesystem

==================



It implements all of

  - Xenix FS,

  - SystemV/386 FS,

  - Coherent FS.



To install:



* Answer the 'System V and Coherent filesystem support' question with 'y'

  when configuring the kernel.

* To mount a disk or a partition, use::



    mount [-r] -t sysv device mountpoint



  The file system type names::



               -t sysv

               -t xenix

               -t coherent



  may be used interchangeably, but the last two will eventually disappear.



Bugs in the present implementation:



- Coherent FS:



  - The "free list interleave" n:m is currently ignored.

  - Only file systems with no filesystem name and no pack name are recognized.

    (See Coherent "man mkfs" for a description of these features.)



- SystemV Release 2 FS:



  The superblock is only searched in the blocks 9, 15, 18, which

  corresponds to the beginning of track 1 on floppy disks. No support

  for this FS on hard disk yet.





These filesystems are rather similar. Here is a comparison with Minix FS:



* Linux fdisk reports on partitions



  - Minix FS     0x81 Linux/Minix

  - Xenix FS     ??

  - SystemV FS   ??

  - Coherent FS  0x08 AIX bootable



* Size of a block or zone (data allocation unit on disk)



  - Minix FS     1024

  - Xenix FS     1024 (also 512 ??)

  - SystemV FS   1024 (also 512 and 2048)

  - Coherent FS   512



* General layout: all have one boot block, one super block and

  separate areas for inodes and for directories/data.

  On SystemV Release 2 FS (e.g. Microport) the first track is reserved and

  all the block numbers (including the super block) are offset by one track.



* Byte ordering of "short" (16 bit entities) on disk:



  - Minix FS     little endian  0 1

  - Xenix FS     little endian  0 1

  - SystemV FS   little endian  0 1

  - Coherent FS  little endian  0 1



  Of course, this affects only the file system, not the data of files on it!



* Byte ordering of "long" (32 bit entities) on disk:



  - Minix FS     little endian  0 1 2 3

  - Xenix FS     little endian  0 1 2 3

  - SystemV FS   little endian  0 1 2 3

  - Coherent FS  PDP-11         2 3 0 1



  Of course, this affects only the file system, not the data of files on it!



* Inode on disk: "short", 0 means non-existent, the root dir ino is:



  =================================  ==

  Minix FS                            1

  Xenix FS, SystemV FS, Coherent FS   2

  =================================  ==



* Maximum number of hard links to a file:



  ===========  =========

  Minix FS     250

  Xenix FS     ??

  SystemV FS   ??

  Coherent FS  >=10000

  ===========  =========



* Free inode management:



  - Minix FS

      a bitmap

  - Xenix FS, SystemV FS, Coherent FS

      There is a cache of a certain number of free inodes in the super-block.

      When it is exhausted, new free inodes are found using a linear search.



* Free block management:



  - Minix FS

      a bitmap

  - Xenix FS, SystemV FS, Coherent FS

      Free blocks are organized in a "free list". Maybe a misleading term,

      since it is not true that every free block contains a pointer to

      the next free block. Rather, the free blocks are organized in chunks

      of limited size, and every now and then a free block contains pointers

      to the free blocks pertaining to the next chunk; the first of these

      contains pointers and so on. The list terminates with a "block number"

      0 on Xenix FS and SystemV FS, with a block zeroed out on Coherent FS.



* Super-block location:



  ===========  ==========================

  Minix FS     block 1 = bytes 1024..2047

  Xenix FS     block 1 = bytes 1024..2047

  SystemV FS   bytes 512..1023

  Coherent FS  block 1 = bytes 512..1023

  ===========  ==========================



* Super-block layout:



  - Minix FS::



                    unsigned short s_ninodes;

                    unsigned short s_nzones;

                    unsigned short s_imap_blocks;

                    unsigned short s_zmap_blocks;

                    unsigned short s_firstdatazone;

                    unsigned short s_log_zone_size;

                    unsigned long s_max_size;

                    unsigned short s_magic;



  - Xenix FS, SystemV FS, Coherent FS::



                    unsigned short s_firstdatazone;

                    unsigned long  s_nzones;

                    unsigned short s_fzone_count;

                    unsigned long  s_fzones[NICFREE];

                    unsigned short s_finode_count;

                    unsigned short s_finodes[NICINOD];

                    char           s_flock;

                    char           s_ilock;

                    char           s_modified;

                    char           s_rdonly;

                    unsigned long  s_time;

                    short          s_dinfo[4]; -- SystemV FS only

                    unsigned long  s_free_zones;

                    unsigned short s_free_inodes;

                    short          s_dinfo[4]; -- Xenix FS only

                    unsigned short s_interleave_m,s_interleave_n; -- Coherent FS only

                    char           s_fname[6];

                    char           s_fpack[6];



    then they differ considerably:



        Xenix FS::



                    char           s_clean;

                    char           s_fill[371];

                    long           s_magic;

                    long           s_type;



        SystemV FS::



                    long           s_fill[12 or 14];

                    long           s_state;

                    long           s_magic;

                    long           s_type;



        Coherent FS::



                    unsigned long  s_unique;



    Note that Coherent FS has no magic.



* Inode layout:



  - Minix FS::



                    unsigned short i_mode;

                    unsigned short i_uid;

                    unsigned long  i_size;

                    unsigned long  i_time;

                    unsigned char  i_gid;

                    unsigned char  i_nlinks;

                    unsigned short i_zone[7+1+1];



  - Xenix FS, SystemV FS, Coherent FS::



                    unsigned short i_mode;

                    unsigned short i_nlink;

                    unsigned short i_uid;

                    unsigned short i_gid;

                    unsigned long  i_size;

                    unsigned char  i_zone[3*(10+1+1+1)];

                    unsigned long  i_atime;

                    unsigned long  i_mtime;

                    unsigned long  i_ctime;





* Regular file data blocks are organized as



  - Minix FS:



             - 7 direct blocks

	     - 1 indirect block (pointers to blocks)

             - 1 double-indirect block (pointer to pointers to blocks)



  - Xenix FS, SystemV FS, Coherent FS:



             - 10 direct blocks

             -  1 indirect block (pointers to blocks)

             -  1 double-indirect block (pointer to pointers to blocks)

             -  1 triple-indirect block (pointer to pointers to pointers to blocks)





  ===========  ==========   ================

               Inode size   inodes per block

  ===========  ==========   ================

  Minix FS        32        32

  Xenix FS        64        16

  SystemV FS      64        16

  Coherent FS     64        8

  ===========  ==========   ================



* Directory entry on disk



  - Minix FS::



                    unsigned short inode;

                    char name[14/30];



  - Xenix FS, SystemV FS, Coherent FS::



                    unsigned short inode;

                    char name[14];



  ===========    ==============    =====================

                 Dir entry size    dir entries per block

  ===========    ==============    =====================

  Minix FS       16/32             64/32

  Xenix FS       16                64

  SystemV FS     16                64

  Coherent FS    16                32

  ===========    ==============    =====================



* How to implement symbolic links such that the host fsck doesn't scream:



  - Minix FS     normal

  - Xenix FS     kludge: as regular files with  chmod 1000

  - SystemV FS   ??

  - Coherent FS  kludge: as regular files with  chmod 1000





Notation: We often speak of a "block" but mean a zone (the allocation unit)

and not the disk driver's notion of "block".

MAINTAINERS

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@@ -23030,12 +23030,6 @@ L: platform-driver-x86@vger.kernel.org 
S:	Maintained

F:	drivers/platform/x86/system76_acpi.c









SYSV FILESYSTEM









S:	Orphan









F:	Documentation/filesystems/sysv-fs.rst









F:	fs/sysv/









F:	include/linux/sysv_fs.h

















TASKSTATS STATISTICS INTERFACE









M:	Balbir Singh <bsingharora@gmail.com>









S:	Maintained

























arch/loongarch/configs/loongson3_defconfig



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@@ -981,7 +981,6 @@ CONFIG_MINIX_FS=m







CONFIG_ROMFS_FS=m









CONFIG_PSTORE=m









CONFIG_PSTORE_COMPRESS=y









CONFIG_SYSV_FS=m









CONFIG_UFS_FS=m









CONFIG_EROFS_FS=m









CONFIG_EROFS_FS_ZIP_LZMA=y
































arch/m68k/configs/amiga_defconfig



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@@ -486,7 +486,6 @@ CONFIG_OMFS_FS=m







CONFIG_HPFS_FS=m









CONFIG_QNX4FS_FS=m









CONFIG_QNX6FS_FS=m









CONFIG_SYSV_FS=m









CONFIG_UFS_FS=m









CONFIG_EROFS_FS=m









CONFIG_NFS_FS=y