linux-kernel - [PATCH v8 9/9] docs: tmpfs: Add casefold options

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Message-Id: <20241021-tonyk-tmpfs-v8-9-f443d5814194@igalia.com>
Date: Mon, 21 Oct 2024 13:37:25 -0300
From: André Almeida <andrealmeid@...lia.com>
To: Gabriel Krisman Bertazi <krisman@...nel.org>, 
 Alexander Viro <viro@...iv.linux.org.uk>, 
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
 Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, 
 Hugh Dickins <hughd@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
 Jonathan Corbet <corbet@....net>, smcv@...labora.com
Cc: kernel-dev@...lia.com, linux-fsdevel@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org, 
 linux-mm@...ck.org, linux-doc@...r.kernel.org, 
 Gabriel Krisman Bertazi <krisman@...e.de>, 
 Randy Dunlap <rdunlap@...radead.org>, 
 André Almeida <andrealmeid@...lia.com>
Subject: [PATCH v8 9/9] docs: tmpfs: Add casefold options

Document mounting options for casefold support in tmpfs.

Reviewed-by: Gabriel Krisman Bertazi <krisman@...e.de>
Reviewed-by: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: André Almeida <andrealmeid@...lia.com>
---
Changes from v3:
- Rewrote note about "this doesn't enable casefold by default" (Krisman)
---
 Documentation/filesystems/tmpfs.rst | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst
index 56a26c843dbe964086503dda9b4e8066a1242d72..d677e0428c3f68148a3761bb232bbed5b9a41f76 100644
--- a/Documentation/filesystems/tmpfs.rst
+++ b/Documentation/filesystems/tmpfs.rst
@@ -241,6 +241,28 @@ So 'mount -t tmpfs -o size=10G,nr_inodes=10k,mode=700 tmpfs /mytmpfs'
 will give you tmpfs instance on /mytmpfs which can allocate 10GB
 RAM/SWAP in 10240 inodes and it is only accessible by root.
 
+tmpfs has the following mounting options for case-insensitive lookup support:
+
+================= ==============================================================
+casefold          Enable casefold support at this mount point using the given
+                  argument as the encoding standard. Currently only UTF-8
+                  encodings are supported. If no argument is used, it will load
+                  the latest UTF-8 encoding available.
+strict_encoding   Enable strict encoding at this mount point (disabled by
+                  default). In this mode, the filesystem refuses to create file
+                  and directory with names containing invalid UTF-8 characters.
+================= ==============================================================
+
+This option doesn't render the entire filesystem case-insensitive. One needs to
+still set the casefold flag per directory, by flipping the +F attribute in an
+empty directory. Nevertheless, new directories will inherit the attribute. The
+mountpoint itself cannot be made case-insensitive.
+
+Example::
+
+    $ mount -t tmpfs -o casefold=utf8-12.1.0,strict_encoding fs_name /mytmpfs
+    $ mount -t tmpfs -o casefold fs_name /mytmpfs
+
 
 :Author:
    Christoph Rohland <cr@....com>, 1.12.01
@@ -250,3 +272,5 @@ RAM/SWAP in 10240 inodes and it is only accessible by root.
    KOSAKI Motohiro, 16 Mar 2010
 :Updated:
    Chris Down, 13 July 2020
+:Updated:
+   André Almeida, 23 Aug 2024

-- 
2.47.0