From a5866298597e2fd460c47d9fda7cceacbe9f3fcb Mon Sep 17 00:00:00 2001
From: Harald Hoyer <harald@redhat.com>
Date: Tue, 24 Nov 2015 09:41:26 +0100
Subject: [PATCH 4/4] core: Do not bind a mount unit to a device, if it was
 from mountinfo

If a mount unit is bound to a device, systemd tries to umount the
mount point, if it thinks the device has gone away.

Due to the uevent queue and inotify of /proc/self/mountinfo being two
different sources, systemd can never get the ordering reliably correct.

It can happen, that in the uevent queue ADD,REMOVE,ADD is queued
and an inotify of mountinfo (or libmount event) happend with the
device in question.

systemd cannot know, at which point of time the mount happend in the
ADD,REMOVE,ADD sequence.

The real ordering might have been ADD,REMOVE,ADD,mount
and systemd might think ADD,mount,REMOVE,ADD and would umount the
mountpoint.

A test script which triggered this behaviour is:
rm -f test-efi-disk.img
dd if=/dev/null of=test-efi-disk.img bs=1M seek=512 count=1
parted --script test-efi-disk.img \
  "mklabel gpt" \
  "mkpart ESP fat32 1MiB 511MiB" \
  "set 1 boot on"
LOOP=$(losetup --show -f -P test-efi-disk.img)
udevadm settle
mkfs.vfat -F32 ${LOOP}p1
mkdir -p mnt
mount ${LOOP}p1 mnt
... <dostuffwith mnt>

Without the "udevadm settle" systemd unmounted mnt while the script was
operating on mnt.

Of course the question is, why there was a REMOVE in the first place,
but this is not part of this patch.

(cherry picked from commit 9d06297e262966de71095debd1537fc223f940a3)

Note: I'm adding a Related note, but I'm not entirely sure if it really is...

Related: #1195761
---
 src/core/mount.c  | 2 +-
 src/core/socket.c | 2 +-
 src/core/swap.c   | 2 +-
 src/core/unit.c   | 6 ++++--
 src/core/unit.h   | 2 +-
 5 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/core/mount.c b/src/core/mount.c
index 9b44357..2ad4ad4 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -335,7 +335,7 @@ static int mount_add_device_links(Mount *m) {
         if (mount_is_auto(p) && UNIT(m)->manager->running_as == MANAGER_SYSTEM)
                 device_wants_mount = true;
 
-        r = unit_add_node_link(UNIT(m), p->what, device_wants_mount);
+        r = unit_add_node_link(UNIT(m), p->what, device_wants_mount, m->from_fragment ? UNIT_BINDS_TO : UNIT_REQUIRES);
         if (r < 0)
                 return r;
 
diff --git a/src/core/socket.c b/src/core/socket.c
index 687675b..860a1e3 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -289,7 +289,7 @@ static int socket_add_device_link(Socket *s) {
                 return 0;
 
         t = strjoina("/sys/subsystem/net/devices/", s->bind_to_device);
-        return unit_add_node_link(UNIT(s), t, false);
+        return unit_add_node_link(UNIT(s), t, false, UNIT_BINDS_TO);
 }
 
 static int socket_add_default_dependencies(Socket *s) {
diff --git a/src/core/swap.c b/src/core/swap.c
index b6e4372..5568898 100644
--- a/src/core/swap.c
+++ b/src/core/swap.c
@@ -202,7 +202,7 @@ static int swap_add_device_links(Swap *s) {
                 return 0;
 
         if (is_device_path(s->what))
-                return unit_add_node_link(UNIT(s), s->what, UNIT(s)->manager->running_as == MANAGER_SYSTEM);
+                return unit_add_node_link(UNIT(s), s->what, UNIT(s)->manager->running_as == MANAGER_SYSTEM, UNIT_BINDS_TO);
         else
                 /* File based swap devices need to be ordered after
                  * systemd-remount-fs.service, since they might need a
diff --git a/src/core/unit.c b/src/core/unit.c
index 0a02e38..e6e67d2 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -2840,7 +2840,7 @@ int unit_deserialize(Unit *u, FILE *f, FDSet *fds) {
         }
 }
 
-int unit_add_node_link(Unit *u, const char *what, bool wants) {
+int unit_add_node_link(Unit *u, const char *what, bool wants, UnitDependency dep) {
         Unit *device;
         _cleanup_free_ char *e = NULL;
         int r;
@@ -2867,7 +2867,9 @@ int unit_add_node_link(Unit *u, const char *what, bool wants) {
         if (r < 0)
                 return r;
 
-        r = unit_add_two_dependencies(u, UNIT_AFTER, u->manager->running_as == MANAGER_SYSTEM ? UNIT_BINDS_TO : UNIT_WANTS, device, true);
+        r = unit_add_two_dependencies(u, UNIT_AFTER,
+                                      u->manager->running_as == MANAGER_SYSTEM ? dep : UNIT_WANTS,
+                                      device, true);
         if (r < 0)
                 return r;
 
diff --git a/src/core/unit.h b/src/core/unit.h
index 1681bbf..3eb3484 100644
--- a/src/core/unit.h
+++ b/src/core/unit.h
@@ -528,7 +528,7 @@ int unit_serialize_item_escaped(Unit *u, FILE *f, const char *key, const char *v
 int unit_serialize_item_fd(Unit *u, FILE *f, FDSet *fds, const char *key, int fd);
 void unit_serialize_item_format(Unit *u, FILE *f, const char *key, const char *value, ...) _printf_(4,5);
 
-int unit_add_node_link(Unit *u, const char *what, bool wants);
+int unit_add_node_link(Unit *u, const char *what, bool wants, UnitDependency d);
 
 int unit_coldplug(Unit *u);
 
-- 
2.5.0