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

From: "André Almeida" <andrealmeid@collabora.com>
To: Hugh Dickins <hughd@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>
Cc: krisman@collabora.com, smcv@collabora.com, kernel@collabora.com,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Daniel Rosenberg" <drosen@google.com>,
	"André Almeida" <andrealmeid@collabora.com>
Subject: [RFC PATCH 4/4] docs: tmpfs: Add casefold options
Date: Tue, 23 Mar 2021 16:59:41 -0300	[thread overview]
Message-ID: <20210323195941.69720-5-andrealmeid@collabora.com> (raw)
In-Reply-To: <20210323195941.69720-1-andrealmeid@collabora.com>

Document mounting options to enable casefold support in tmpfs.

Signed-off-by: André Almeida <andrealmeid@collabora.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@sap.com>, 1.12.01
-- 
2.31.0

