[PATCH v3 1/2] name_to_handle_at.2: Document the AT_HANDLE_MNT_ID_UNIQUE flag

[Amir Goldstein <amir73il@gmail.com>]

A flag since v6.12 to indicate that the requested mount_id is
a 64bit unique id.

Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 man/man2/open_by_handle_at.2 | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/man/man2/open_by_handle_at.2 b/man/man2/open_by_handle_at.2
index 6b9758d42..e3ec70dd5 100644
--- a/man/man2/open_by_handle_at.2
+++ b/man/man2/open_by_handle_at.2
@@ -127,6 +127,7 @@ The
 .I flags
 argument is a bit mask constructed by ORing together zero or more of
 .BR AT_HANDLE_FID ,
+.BR AT_HANDLE_MNT_ID_UNIQUE,
 .BR AT_EMPTY_PATH ,
 and
 .BR AT_SYMLINK_FOLLOW ,
@@ -147,6 +148,21 @@ with the returned
 .I file_handle
 may fail.
 .P
+When
+.I flags
+contain the
+.BR AT_HANDLE_MNT_ID_UNIQUE " (since Linux 6.12)"
+.\" commit 4356d575ef0f39a3e8e0ce0c40d84ce900ac3b61
+flag, the caller indicates that the size of the
+.I mount_id
+buffer is at least 64bit
+and then the mount id returned in that buffer
+is the unique mount id as the one returned by
+.BR statx (2)
+with the
+.BR STATX_MNT_ID_UNIQUE
+flag.
+.P
 Together, the
 .I pathname
 and
-- 
2.34.1