linux-kernel - [PATCH] Documentation: ext4: Document casefold and encrypt flags

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Message-ID: <4506189.9SDvczpPoe@daniel-desktop3>
Date: Wed, 19 Nov 2025 09:32:13 -0500
From: Daniel Tang <danielzgtg.opensource@...il.com>
To: linux-doc@...r.kernel.org, linux-ext4@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
 Eric Biggers <ebiggers@...gle.com>,
 Gabriel Krisman Bertazi <krisman@...labora.co.uk>,
 "Darrick J. Wong" <darrick.wong@...cle.com>
Subject: [PATCH] Documentation: ext4: Document casefold and encrypt flags

Based on ext4(5) and fs/ext4/ext4.h.

For INCOMPAT_ENCRYPT, it's possible to create a new filesystem with that
flag without creating any encrypted inodes. ext4(5) says it adds
"support" but doesn't say whether anything's actually present like
COMPAT_RESIZE_INODE does.

Signed-off-by: Daniel Tang <danielzgtg.opensource@...il.com>
---
 Documentation/filesystems/ext4/inodes.rst | 2 ++
 Documentation/filesystems/ext4/super.rst  | 4 +++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/ext4/inodes.rst b/Documentation/filesystems/ext4/inodes.rst
index cfc6c1659931..55cd5c380e92 100644
--- a/Documentation/filesystems/ext4/inodes.rst
+++ b/Documentation/filesystems/ext4/inodes.rst
@@ -297,6 +297,8 @@ The ``i_flags`` field is a combination of these values:
      - Inode has inline data (EXT4_INLINE_DATA_FL).
    * - 0x20000000
      - Create children with the same project ID (EXT4_PROJINHERIT_FL).
+   * - 0x40000000
+     - Use case-insensitive lookups for directory contents (EXT4_CASEFOLD_FL).
    * - 0x80000000
      - Reserved for ext4 library (EXT4_RESERVED_FL).
    * -
diff --git a/Documentation/filesystems/ext4/super.rst b/Documentation/filesystems/ext4/super.rst
index 1b240661bfa3..9a59cded9bd7 100644
--- a/Documentation/filesystems/ext4/super.rst
+++ b/Documentation/filesystems/ext4/super.rst
@@ -671,7 +671,9 @@ following:
    * - 0x8000
      - Data in inode (INCOMPAT_INLINE_DATA).
    * - 0x10000
-     - Encrypted inodes are present on the filesystem. (INCOMPAT_ENCRYPT).
+     - Encrypted inodes can be present. (INCOMPAT_ENCRYPT).
+   * - 0x20000
+     - Directories can be marked case-insensitive. (INCOMPAT_CASEFOLD).

 .. _super_rocompat:

-- 
2.51.0