From 441ec80468d17a548c8c85e39a0b0e74b75f2650 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 21 May 2019 18:04:04 +0200
Subject: [PATCH] loop-util: add api for locking the block device with flock()

---
 src/shared/loop-util.c | 13 +++++++++++++
 src/shared/loop-util.h |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/src/shared/loop-util.c b/src/shared/loop-util.c
index b1d07fe708..f9be08bf35 100644
--- a/src/shared/loop-util.c
+++ b/src/shared/loop-util.c
@@ -3,6 +3,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <linux/loop.h>
+#include <sys/file.h>
 #include <sys/ioctl.h>
 
 #include "alloc-util.h"
@@ -233,3 +234,15 @@ int loop_device_refresh_size(LoopDevice *d, uint64_t offset, uint64_t size) {
 
         return 0;
 }
+
+int loop_device_flock(LoopDevice *d, int operation) {
+        assert(d);
+
+        if (d->fd < 0)
+                return -EBADF;
+
+        if (flock(d->fd, operation) < 0)
+                return -errno;
+
+        return 0;
+}
diff --git a/src/shared/loop-util.h b/src/shared/loop-util.h
index e5a0ae75b8..5156b46ad6 100644
--- a/src/shared/loop-util.h
+++ b/src/shared/loop-util.h
@@ -28,3 +28,5 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(LoopDevice*, loop_device_unref);
 void loop_device_relinquish(LoopDevice *d);
 
 int loop_device_refresh_size(LoopDevice *d, uint64_t offset, uint64_t size);
+
+int loop_device_flock(LoopDevice *d, int operation);