linux-kernel - [RFC PATCH 4/4] docs: tmpfs: Add casefold options

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Date:   Tue, 23 Mar 2021 16:59:41 -0300
From:   André Almeida <andrealmeid@...labora.com>
To:     Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     krisman@...labora.com, smcv@...labora.com, kernel@...labora.com,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, Daniel Rosenberg <drosen@...gle.com>,
        André Almeida <andrealmeid@...labora.com>
Subject: [RFC PATCH 4/4] docs: tmpfs: Add casefold options

Document mounting options to enable casefold support in tmpfs.

Signed-off-by: André Almeida <andrealmeid@...labora.com>
---
 Documentation/filesystems/tmpfs.rst | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Documentation/filesystems/tmpfs.rst b/Documentation/filesystems/tmpfs.rst
index 0408c245785e..84c87c309bd7 100644
--- a/Documentation/filesystems/tmpfs.rst
+++ b/Documentation/filesystems/tmpfs.rst
@@ -170,6 +170,32 @@ 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-insesitive lookups support:
+
+=========   ==============================================================
+casefold    Enable casefold support at this mount point using the given
+            argument as enconding. Currently only utf8 encondings are supported.
+cf_strict   Enable strict casefolding at this mouting point (disabled by
+            default). This means that invalid strings should be reject by the
+            file system.
+=========   ==============================================================
+
+Note that this option doesn't enable casefold by default, one needs to set
+casefold flag per directory, setting the +F attribute in an empty directory. New
+directories within a casefolded one will inherit the flag.
+
+Example::
+
+    $ mount -t tmpfs -o casefold=utf8-12.1.0,cf_strict tmpfs /mytmpfs
+    $ cd /mytmpfs
+    $ touch a; touch A
+    $ ls
+    A  a
+    $ mkdir dir
+    $ chattr +F dir
+    $ touch dir/a; touch dir/A
+    $ ls dir
+    a
 
 :Author:
    Christoph Rohland <cr@....com>, 1.12.01
-- 
2.31.0