docs: Remove outdated highuid.rst documentation

The highuid.rst document describes a transition that is outdated and no
longer relevant. Additionally, it references filesystems (ncpfs and smbfs),
which have been removed or replaced.

Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Kang Taeho <kangtaeho2456@gmail.com>
Link: https://lore.kernel.org/r/20250313145650.278346-1-kangtaeho2456@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/admin-guide/highuid.rst

@@ -1,80 +0,0 @@
-===================================================
-Notes on the change from 16-bit UIDs to 32-bit UIDs
-===================================================
-
-:Author: Chris Wing <wingc@umich.edu>
-:Last updated: January 11, 2000
-
-- kernel code MUST take into account __kernel_uid_t and __kernel_uid32_t
-  when communicating between user and kernel space in an ioctl or data
-  structure.
-
-- kernel code should use uid_t and gid_t in kernel-private structures and
-  code.
-
-What's left to be done for 32-bit UIDs on all Linux architectures:
-
-- Disk quotas have an interesting limitation that is not related to the
-  maximum UID/GID. They are limited by the maximum file size on the
-  underlying filesystem, because quota records are written at offsets
-  corresponding to the UID in question.
-  Further investigation is needed to see if the quota system can cope
-  properly with huge UIDs. If it can deal with 64-bit file offsets on all 
-  architectures, this should not be a problem.
-
-- Decide whether or not to keep backwards compatibility with the system
-  accounting file, or if we should break it as the comments suggest
-  (currently, the old 16-bit UID and GID are still written to disk, and
-  part of the former pad space is used to store separate 32-bit UID and
-  GID)
-
-- Need to validate that OS emulation calls the 16-bit UID
-  compatibility syscalls, if the OS being emulated used 16-bit UIDs, or
-  uses the 32-bit UID system calls properly otherwise.
-
-  This affects at least:
-
-	- iBCS on Intel
-
-	- sparc32 emulation on sparc64
-	  (need to support whatever new 32-bit UID system calls are added to
-	  sparc32)
-
-- Validate that all filesystems behave properly.
-
-  At present, 32-bit UIDs _should_ work for:
-
-	- ext2
-	- ufs
-	- isofs
-	- nfs
-	- coda
-	- udf
-
-  Ioctl() fixups have been made for:
-
-	- ncpfs
-	- smbfs
-
-  Filesystems with simple fixups to prevent 16-bit UID wraparound:
-
-	- minix
-	- sysv
-	- qnx4
-
-  Other filesystems have not been checked yet.
-
-- The ncpfs and smpfs filesystems cannot presently use 32-bit UIDs in
-  all ioctl()s. Some new ioctl()s have been added with 32-bit UIDs, but
-  more are needed. (as well as new user<->kernel data structures)
-
-- The ELF core dump format only supports 16-bit UIDs on arm, i386, m68k,
-  sh, and sparc32. Fixing this is probably not that important, but would
-  require adding a new ELF section.
-
-- The ioctl()s used to control the in-kernel NFS server only support
-  16-bit UIDs on arm, i386, m68k, sh, and sparc32.
-
-- make sure that the UID mapping feature of AX25 networking works properly
-  (it should be safe because it's always used a 32-bit integer to
-  communicate between user and kernel)

Documentation/admin-guide/index.rst

@@ -187,7 +187,6 @@ A few hard-to-categorize and generally obsolete documents.
 .. toctree::
    :maxdepth: 1
 
-   highuid
    ldm
    unicode