[PATCH] btrfs-progs: docs: document the temp_fsid feature in btrfs(5)

[Anand Jain <asj@kernel.org>]

From: Your Name <you@example.com>

The temp_fsid feature (kernel 6.7) is missing from the FILESYSTEM
FEATURES list in btrfs(5). It's exposed in sysfs
(/sys/fs/btrfs/features/temp_fsid and /sys/fs/btrfs/<UUID>/temp_fsid)
like any other feature, but has no corresponding entry in the manual
page.

Add an entry describing what it does, when it applies (single-device
filesystems only) and its exclusivity with metadata_uuid, following
the existing entry format and alphabetical ordering.

Signed-off-by: Anand Jain <asj@kernel.org>
---
 Documentation/btrfs-man5.rst | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/btrfs-man5.rst b/Documentation/btrfs-man5.rst
index ce4021ab84b5..2635f06a1394 100644
--- a/Documentation/btrfs-man5.rst
+++ b/Documentation/btrfs-man5.rst
@@ -199,6 +199,22 @@ supported_rescue_options
         list of values for the mount option *rescue* that are supported by the running
         kernel, see :doc:`btrfs-man5`
 
+temp_fsid
+	(since: 6.7)
+
+	indicates the filesystem is mounted using a randomly generated, in-memory only
+	substitute for the on-disk filesystem UUID, needed because another filesystem
+	exposing the same UUID (e.g. a block-level clone) is already mounted. The
+	on-disk UUID, as reported by :command:`blkid`, is unchanged; the statfs
+	filesystem ID *f_fsid* returned by :manref:`statfs(2)` for this mount reflects
+	the substitute, and is regenerated on every such mount.
+
+	Supported only for single-device filesystems, mutually exclusive with
+	*metadata_uuid*, and disables :command:`device add` for the mount. To make a
+	clone permanently independent instead of relying on temp_fsid on every mount,
+	change its on-disk UUID with :doc:`btrfstune` (*-u* or *-U*) while unmounted.
+	See also section :ref:`SYSFS INTERFACE<man-btrfs5-sysfs-interface>`.
+
 vefity
         (since: 5.15, CONFIG_FS_VERITY)
 
-- 
2.43.0