[PATCH] fcntl.2: document F_UNLCK F_OFD_GETLK extension

[Stas Sergeev <stsp2@yandex.ru>]

F_UNLCK has the special meaning when used as a lock type on input.
It returns the information about any lock found in the specified
region on that particular file descriptor. Locks on other file
descriptors are ignored by F_UNLCK.

Signed-off-by: Stas Sergeev <stsp2@yandex.ru>

CC: Jeff Layton <jlayton@kernel.org>
CC: Chuck Lever <chuck.lever@oracle.com>
CC: Alexander Viro <viro@zeniv.linux.org.uk>
CC: Christian Brauner <brauner@kernel.org>
CC: linux-fsdevel@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: Shuah Khan <shuah@kernel.org>
CC: linux-kselftest@vger.kernel.org
CC: linux-api@vger.kernel.org

---
 man2/fcntl.2 | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/man2/fcntl.2 b/man2/fcntl.2
index 7b5604e3a..e3e3e7b8c 100644
--- a/man2/fcntl.2
+++ b/man2/fcntl.2
@@ -604,6 +604,13 @@ then details about one of these locks are returned via
 .IR lock ,
 as described above for
 .BR F_GETLK .
+.B F_UNLCK
+has the special meaning when put into
+.I l_type
+as an input. It returns the information about any lock in the specified
+range on that particular file descriptor. The locks on other file
+descriptors are ignored by
+.BR F_UNLCK .
 .PP
 In the current implementation,
 .\" commit 57b65325fe34ec4c917bc4e555144b4a94d9e1f7
-- 
2.39.2