From 4ca8072fd6195c0d8e1c0da24db6b67a97070260 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 20 Dec 2019 18:37:24 +0100
Subject: [PATCH] umount: when we fail to detach a loopback device, set the
 auto-clear flag

We might get lucky and this cleans up things later on automatically for
us.
---
 src/shutdown/umount.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/src/shutdown/umount.c b/src/shutdown/umount.c
index cc86f4180e..8a5e80eeaa 100644
--- a/src/shutdown/umount.c
+++ b/src/shutdown/umount.c
@@ -340,7 +340,30 @@ static int delete_loopback(const char *device) {
                 if (errno == ENXIO) /* Nothing bound, didn't do anything */
                         return 0;
 
-                return -errno;
+                if (errno != EBUSY)
+                        return log_debug_errno(errno, "Failed to clear loopback device %s: %m", device);
+
+                if (ioctl(fd, LOOP_GET_STATUS64, &info) < 0) {
+                        if (errno == ENXIO) /* What? Suddenly detached after all? That's fine by us then. */
+                                return 1;
+
+                        log_debug_errno(errno, "Failed to invoke LOOP_GET_STATUS64 on loopback device %s, ignoring: %m", device);
+                        return -EBUSY; /* propagate original error */
+                }
+
+                if (FLAGS_SET(info.lo_flags, LO_FLAGS_AUTOCLEAR)) /* someone else already set LO_FLAGS_AUTOCLEAR for us? fine by us */
+                        return -EBUSY; /* propagate original error */
+
+                info.lo_flags |= LO_FLAGS_AUTOCLEAR;
+                if (ioctl(fd, LOOP_SET_STATUS64, &info) < 0) {
+                        if (errno == ENXIO) /* Suddenly detached after all? Fine by us */
+                                return 1;
+
+                        log_debug_errno(errno, "Failed to set LO_FLAGS_AUTOCLEAR flag for loop device %s, ignoring: %m", device);
+                } else
+                        log_debug("Successfully set LO_FLAGS_AUTOCLEAR flag for loop device %s.", device);
+
+                return -EBUSY;
         }
 
         if (ioctl(fd, LOOP_GET_STATUS64, &info) < 0) {